Genetics of Breast and Gynecologic Cancers (PDQ®)
Genetics of Breast and Gynecologic Cancers includes the hereditary cancer syndromes BRCA1/BRCA2 (hereditary breast and ovarian cancer), Lynch syndrome, Li Fraumeni syndrome, ATM, PALB2, CHEK2 and other genes. Get comprehensive information on these syndromes in this clinician summary.
https://www.cancer.gov/profiles/custom/cgov_site/themes/custom/cgov/static/images/design-elements/icons/favicons/favicon.ico
Genetics of Breast and Gynecologic Cancers (PDQ®)–Health Professional Version

Executive Summary

This executive summary reviews the topics covered in this PDQ summary on the genetics of breast and gynecologic cancers.

Inheritance and Risk

Factors suggestive of a genetic contribution to both breast cancer and gynecologic cancer include 1) an increased incidence of these cancers among individuals with a family history of these cancers; 2) multiple family members affected with these and other cancers; and 3) a pattern of cancers compatible with autosomal dominant inheritance. Both males and females can inherit and transmit an autosomal dominant cancer predisposition gene.

Additional factors coupled with family history can influence an individual's risk of developing cancer—such as reproductive history, contraceptive and hormone replacement use, radiation exposure early in life, alcohol consumption and smoking, and physical activity.

Risk assessment models have been developed to clarify an individual's 1) lifetime risk of developing breast and/or gynecologic cancer; 2) likelihood of having a pathogenic variant in BRCA1 or BRCA2; and 3) likelihood of having a pathogenic variant in one of the mismatch repair genes associated with Lynch syndrome.

Associated Genes and Syndromes

Breast and ovarian cancer are present in several autosomal dominant cancer syndromes, although they are most strongly associated with highly penetrant germline pathogenic variants in BRCA1 and BRCA2. Other genes, such as PALB2, TP53 (associated with Li-Fraumeni syndrome), PTEN (associated with PTEN hamartoma tumor syndromes, including Cowden syndrome), CDH1 (associated with diffuse gastric and lobular breast cancer syndrome), and STK11 (associated with Peutz-Jeghers syndrome), confer a risk to either or both of these cancers with relatively high penetrance.

Inherited endometrial cancer is most commonly associated with Lynch syndrome, a condition caused by inherited pathogenic variants in the highly penetrant mismatch repair genes MLH1, MSH2, MSH6, PMS2, and EPCAM. Colorectal cancer (and, to a lesser extent, ovarian cancer and stomach cancer) is also associated with Lynch syndrome.

CHEK2, BRIP1, RAD51C, RAD51D, and ATM are moderate penetrance genes that are associated with increased breast and/or gynecologic cancer risk. Genome-wide searches are showing promise in identifying common, low-penetrance susceptibility alleles for many complex diseases, including breast and gynecologic cancers, but the clinical utility of these findings remains uncertain.

Clinical Management

Breast cancer screening strategies, including breast magnetic resonance imaging and mammography, are commonly performed in carriers of BRCA pathogenic variants and in individuals at increased risk of breast cancer. Initiation of screening is generally recommended at earlier ages and at more frequent intervals in individuals with an increased risk due to genetics and family history than in the general population. There is evidence to demonstrate that these strategies have utility in early detection of cancer. In contrast, there is currently no evidence to demonstrate that ovarian cancer screening using cancer antigen–125 testing and transvaginal ultrasound leads to early detection of cancer.

Risk-reducing surgeries, including risk-reducing mastectomy (RRM) and risk-reducing salpingo-oophorectomy (RRSO), have been shown to significantly reduce the risk of developing breast and/or ovarian cancer and improve overall survival in carriers of BRCA1 and BRCA2 pathogenic variants. Chemoprevention strategies for breast cancer and chemoprevention strategies for ovarian cancer have been examined in this population. For example, tamoxifen use has been shown to reduce the risk of contralateral breast cancer among carriers of BRCA1 and BRCA2 pathogenic variants after treatment for breast cancer, but there are limited data in the primary cancer prevention setting to suggest that it reduces the risk of breast cancer among healthy female carriers of BRCA2 pathogenic variants. The use of OCs also has been associated with a protective effect on the risk of developing ovarian cancer, including in carriers of BRCA1 and BRCA2 pathogenic variants, with no association of increased risk of breast cancer when using formulations developed after 1975.

Psychosocial and Behavioral Issues

Psychosocial factors influence decisions about genetic testing for inherited cancer risk and risk-management strategies. Uptake of genetic testing varies widely across studies. Psychological factors that have been associated with testing uptake include cancer-specific distress and perceived risk of developing breast or ovarian cancer. Studies have shown low levels of distress after genetic testing for both carriers and noncarriers, particularly in the longer term. Uptake of RRM and RRSO also varies across studies and may be influenced by factors such as cancer history, age, family history, recommendations of the health care provider, and pretreatment genetic education and counseling. Patients' communication with their family members about an inherited risk of breast and gynecologic cancer is complex; gender, age, and the degree of relatedness are some elements that affect disclosure of this information. Research is ongoing to better understand and address psychosocial and behavioral issues in high-risk families.

Introduction

General Information

Among women in the United States, breast cancer is the most commonly diagnosed cancer after nonmelanoma skin cancer, and it is the second leading cause of cancer deaths after lung cancer. In 2024, an estimated 313,510 new cases of breast cancer (including 2,790 cases in men) will be diagnosed, and 42,780 deaths (including 530 deaths in men) will occur.[1] The incidence of breast cancer, particularly for estrogen receptor (ER)–positive cancers occurring after age 50 years, is declining and has declined at a faster rate since 2003. This may be temporally related to a decrease in hormone replacement therapy (HRT) after early reports from the Women’s Health Initiative (WHI).[2] An estimated 19,680 new cases of ovarian cancer are expected in the United States in 2024, with an estimated 12,740 deaths. Ovarian cancer is the sixth most deadly cancer in women.[1] An estimated 67,880 new cases of endometrial cancer are expected in the United States in 2024, with an estimated 13,250 deaths.[1] (Refer to the PDQ summaries on Breast Cancer Treatment; Ovarian Epithelial, Fallopian Tube, and Primary Peritoneal Cancer Treatment; and Endometrial Cancer Treatment for more information about breast, ovarian, and endometrial cancer rates, diagnosis, and management.)

A possible genetic contribution to both breast and ovarian cancer risk is indicated by the increased incidence of these cancers among women with a family history (refer to the Risk Factors for Breast Cancer, Risk Factors for Ovarian Cancer, and Risk Factors for Endometrial Cancer sections below for more information), and by the observation of some families in which multiple family members are affected with breast and/or ovarian cancer, in a pattern compatible with an inheritance of autosomal dominant cancer susceptibility. Formal studies of families (linkage analysis) have subsequently proven the existence of autosomal dominant predispositions to breast and ovarian cancer and have led to the identification of several highly penetrant genes as the cause of inherited cancer risk in many families. (Refer to the PDQ summary Cancer Genetics Overview for more information about linkage analysis.) Pathogenic variants in these genes are rare in the general population and are estimated to account for no more than 5% to 10% of breast and ovarian cancer cases overall. It is likely that other genetic factors contribute to the etiology of some of these cancers.

Risk Factors for Breast Cancer

This section discusses factors that can modify an individual's risk of developing breast cancer. These risk factors can affect women in the general population, women who have a family histories of breast cancer, and women who carry pathogenic variants in breast cancer risk genes. For more information on breast cancer risk factors in the general population, see Breast Cancer Prevention, and for more information on risks associated with BRCA1/2 pathogenic variants, see the Cancer Risks, Spectrum, and Characteristics section in BRCA1 and BRCA2: Cancer Risks and Management.

The following breast cancer risk factors are discussed in this section:

These factors can increase or decrease breast cancer risk in all women. However, they may affect breast cancer risk differently in women with increased breast cancer susceptibility (i.e., women who have high-risk family histories and/or pathogenic variants in hereditary breast cancer genes). Factors that increase breast cancer risk in the general population may lower breast cancer risk, increase breast cancer risk more than expected, or have no effect on breast cancer risk in women with high breast cancer susceptibility. In some cases, these risk factors may affect high-risk women in the same way that they affect average-risk women. Furthermore, modifying risk factors has a greater effect on the absolute breast cancer risk in women with high breast cancer susceptibility than in women with low breast cancer susceptibility.[3] It is imperative that providers discuss breast cancer risk factors with high-susceptibility patients, since risk patterns deviate from those seen in women in the general population. Providers may also want to convey whether these risk factors increase, decrease, or do not affect breast cancer risk in women with high breast cancer susceptibility, based on available evidence. This information may change how providers approach breast cancer risk management in women with high breast cancer susceptibility.

Age

Like other cancer types, breast cancer's cumulative risk increases with age. As individuals age, they encounter more environmental exposures and accumulate genomic changes. Hence, most breast cancers occur after age 50 years.[4] Women with pathogenic variants in breast cancer risk genes often develop breast cancer at younger ages than women with sporadic breast cancers.

Family history of breast cancer

A family history of breast cancer is a well-established, consistent risk factor for breast cancer. Approximately 5% to 10% of women with breast cancer also had a mother or sister with breast cancer in cross-sectional studies. About 10% to 20% of women had a first-degree relative (FDR) or a second-degree relative (SDR) with breast cancer.[5-8] A pooled analysis of 38 studies showed that women had increased breast cancer risk when they had at least one FDR with breast cancer (relative risk [RR], 2.1; 95% confidence interval [CI], 2.0–2.2).[9] A large population-based study that used the Swedish Family Cancer Database found that women had a significantly increased risk of breast cancer when they had a mother or a sister with breast cancer.[6,7,9-11]

The following factors can increase a woman's breast cancer risk:

Large number of affected relatives.

Family members who were diagnosed with breast cancer at young ages.

Family members with bilateral breast cancers.

Family members with multiple ipsilateral breast cancers.

Male relatives with breast cancer.

Furthermore, women with family histories of multiple breast cancers had higher hazard ratios (HRs) (HR, 2.7; 95% CI, 2.6–2.9) than women who had a single breast cancer in their families (HR, 1.8; 95% CI, 1.8–1.9). When women had multiple breast cancers in their families (with one breast cancer occurring before age 40 years), the HR was 3.8 (95% CI, 3.1–4.8). However, breast cancer risk also significantly increased when a relative was diagnosed with breast cancer at 60 years or older, suggesting that having a relative with breast cancer at any age can increase risk.[11] Another study in women with unilateral versus contralateral breast cancer (CBC) evaluated CBC risk among family members.[12] Results indicated that women with at least one affected FDR had an 8.1% chance of developing CBC after 10 years. Participants' risks also increased when relatives were diagnosed with breast cancer before age 40 years (10-year absolute risk [AR], 13.5%; 95% CI, 8.8%–20.8%) or if relatives had CBC (10-year AR, 14.1%; 95% CI, 9.5%–20.7%). These risks were similar to those seen among BRCA carriers (10-year AR, 18.4%; 95% CI, 16.0%–21.3%). These risk estimates remained unchanged when the analysis was restricted to women who tested negative for a pathogenic variant in BRCA1/BRCA2, ATM, CHEK2, or PALB2.

Albright et al. addressed how affected third-degree relatives (TDRs) can contribute to an individual's breast cancer risk.[13] These researchers used the Utah Population Database and the Utah Cancer Registry to estimate RRs for participants to develop breast cancer. They collected family histories with FDRs, SDRs, and TDRs and included both paternal and maternal relatives. They confirmed that individuals with affected FDRs had the highest breast cancer risk, particularly if the FDR was diagnosed with breast cancer early in life. When participants had five or more affected TDRs (and no FDRs/SDRs with breast cancer), they had an RR of 1.32 (95% CI, 1.11–1.57).

One of the largest studies of twins ever conducted examined 80,309 monozygotic twins and 123,382 dizygotic twins. This study had a heritability estimate of 31% for breast cancer (95% CI, 11%–51%).[14] If a monozygotic twin had breast cancer, her twin sister had a 28.1% chance of developing breast cancer (95% CI, 23.9%–32.8%), and if a dizygotic twin had breast cancer, her twin sister had a 19.9% chance of developing breast cancer (95% CI, 17%–23.2%). These estimates suggest that monozygotic twins have a 10% higher risk of developing breast cancer than dizygotic twins. However, the high rate of discordance seen, even between monozygotic twins, suggests that environmental factors can also modify breast cancer risk.

Benign breast disease, mammographic density, and background parenchymal enhancement

Benign breast disease (BBD)

BBD is a broad group of conditions characterized by non-cancerous changes in breast tissue. BBD can be divided into three categories: nonproliferative lesions, proliferative lesions without atypia, and atypical hyperplasias. BBD is a consistent risk factor for breast cancer in the general population.[15,16]

BBD is also an important risk factor in women who have high breast cancer susceptibility due to family histories of cancer or pathogenic variants in breast cancer risk genes. For example, a study of 17,154 women found that women with a history of BBD have an increased risk of breast cancer that is independent of their underlying familial and genetic risks.[17] However, breast cancer risk associated with personal histories of BBD did not vary between women with BRCA1 pathogenic variants (RR, 1.64; 95% CI, 1.04–2.58), women with BRCA2 pathogenic variants (RR, 1.34; 95% CI, 0.78–2.3), and women who only had family histories of breast cancer (RR, 1.31; 95% CI, 1.13–1.53). In women with high breast cancer susceptibility, BBD can further increase breast cancer risk, because it multiplies their underlying familial and genetic risks.

Mammographic density

Women with dense breast tissue (assessed by mammogram) also have an increased risk of developing breast cancer.[15,18,19] Studies have shown that breast density likely has a genetic etiology.[20-22]

A systematic review reported that women who had dense breast tissue and an FDR with breast cancer had an increased chance of developing breast cancer.[23] Two retrospective studies also investigated the association between mammographic density and breast cancer risk in BRCA1 and BRCA2 carriers.[24,25] These retrospective studies had samples of 206 and 691 BRCA pathogenic variant carriers. In these studies, 96 and 248 women developed breast cancer, respectively.[24,25] The studies found that mammographic density is an independent risk factor for breast cancer in both BRCA1 and BRCA2 pathogenic variant carriers. Associations between breast density and breast cancer risk were similar to those observed in the general population (RR, 2.30 for density ≥50% vs. <50%).

Background parenchymal enhancement (BPE)

Like breast density (assessed by mammogram), BPE (assessed by breast magnetic resonance imaging [MRI]) may increase breast cancer risk. Data have shown that moderate BPE (odds ratio [OR], 1.6; 95% CI, 1.0–2.6) and mild BPE (OR, 2.1; 95% CI, 1.5–3.0) can increase breast cancer risk in women with high breast cancer susceptibility. However, an association between mild/moderate BPE and breast cancer risk was not found in women with average breast cancer susceptibility.[26]

Parity, age at first birth, and breastfeeding

Parity

A large prospective study analyzed the relationship between parity and breast cancer risk in female BRCA1 and BRCA2 carriers. Results showed that parity affected breast cancer risk in BRCA1 and BRCA2 carriers differently. Breast cancer risk increased in uniparous BRCA1 carriers and parous BRCA2 carriers.[27] In BRCA1 carriers, there was no overall association between parity and breast cancer risk when compared with nulliparity and breast cancer risk. Uniparous BRCA1 carriers were at an increased risk of breast cancer in the prospective analysis (HRprospective , 1.69; 95% CI, 1.09–2.62) when compared with nulliparous BRCA1 carriers. The results also suggested that uniparous women who breastfed may have decreased breast cancer risk when compared with those who did not breastfeed. In BRCA2 carriers, being parous was associated with a 33% increase in breast cancer risk (HRcombined , 1.33; 95% CI, 1.05–1.69). Multiparity did not decrease breast cancer risk in BRCA2 carriers, unless they had at least four full-term pregnancies (HRcombined, 0.72; 95% CI, 0.54–0.98).

Age at first birth

In the general population, breast cancer risk increases when women have early menarche and/or late menopause. Breast cancer risk decreases when a woman’s first full-term pregnancy occurs at a young age. However, these risk factors can affect women with high breast cancer susceptibility differently than women in the general population. BRCA1 and BRCA2 pathogenic variant carriers who become pregnant prior to age 30 years may have increased breast cancer risk. This effect is even more significant in BRCA1 pathogenic variant carriers.[28-30] BRCA1 and BRCA2 pathogenic variant carriers who developed breast cancer during pregnancy or became pregnant after developing breast cancer did not experience adverse survival outcomes.[31]

Breastfeeding

Breastfeeding can reduce breast cancer risk in BRCA1 (but not BRCA2) pathogenic variant carriers.[32] Breastfeeding for long periods of time was associated with decreased breast cancer risk in BRCA1 carriers (P-trend = .0003).[27]

Reproductive history can also affect a woman's risk for ovarian cancer and endometrial cancer. For more information, see the Risk Factors for Ovarian Cancer and Risk Factors for Endometrial Cancer sections.

Contraceptives

Breast cancer risk is one of the factors to consider when prescribing contraceptives, which assist with pregnancy control, abnormal bleeding, and other gynecological symptoms. Oral contraceptives (OCs) may slightly increase breast cancer risk in long-term users, but this appears to be a short-term effect.[33]

Some studies show that OC use does not further increase breast cancer risk in women with high breast cancer susceptibility. For example, a meta-analysis with data from 54 studies showed that women with family histories of breast cancer did not have increased breast cancer risk from OC use.[33] Although the data are not entirely consistent, a meta-analysis of BRCA1/BRCA2 pathogenic variant carriers concluded that breast cancer risk did not significantly increase when participants used OCs.[34] More specifically, the International BRCA1/2 Carrier Cohort Study (IBCCS), the Kathleen Cuningham Foundation Consortium for Research into Familial Breast Cancer (kConFab) Follow-Up Study, and the Breast Cancer Family Registry (BCFR) did not report associations between OC use and increased breast cancer risk in women with BRCA1 pathogenic variants.[35] In fact, OCs are sometimes recommended for ovarian cancer prevention in BRCA1 and BRCA2 pathogenic variant carriers. For more information, see the Oral contraceptives and Risk Factors for Ovarian Cancer sections. However, in the prospective analyses of the IBCCS, kConFab, and BCFR studies mentioned above, women with BRCA2 pathogenic variants had increased breast cancer risk when they took OCs (HR, 1.75; 95% CI, 1.03–2.97). Additionally, a systematic review of the published data concluded that it is unclear if OC use increases breast cancer risk in BRCA1/2 carriers due to inconsistencies across studies.[36]

Some studies also suggest that the year an OC was made and a woman's age when beginning OC use may matter. For example, OCs made before 1975 are associated with increased breast cancer risk in BRCA1/2 carriers (summary relative risk [SRR], 1.47; 95% CI, 1.06–2.04).[34] A case-control study of 2,492 matched pairs of women with a BRCA1 pathogenic variant also found that OC use significantly increased breast cancer risk when women began using OCs prior to age 20 years (OR, 1.45; 95% CI, 1.20–1.75).[37]

Other contraceptive methods have not been studied in women with pathogenic variants in breast cancer risk genes. However, studies have investigated associations between intrauterine devices and breast cancer risk in the general population. A meta-analysis and systematic review of seven studies examined the effect of the levonorgestrel-releasing intrauterine system (LNG-IUS) on breast cancer risk. The meta-analysis included studies that controlled for family history of breast cancer, but associations were not separately evaluated or stratified by family history of breast cancer. In LNG-IUS users, breast cancer risk increased in all women (OR, 1.16; 95% CI, 1.06–1.28), in women younger than 50 years (OR, 1.12; 95% CI, 1.02–1.22), and in women 50 years and older (OR, 1.52; 95% CI, 1.34–1.72).[38]

Hormone replacement therapy

Both observational studies and randomized clinical trials have examined the association between postmenopausal HRT and breast cancer. Short-term use of HRT for treatment of postmenopausal symptoms appears to confer little or no breast cancer risk.[39,40] A meta-analysis with data from 51 observational studies found a 1.35 RR for breast cancer (95% CI, 1.21–1.49) in women who used HRT for 5 or more years after menopause.[39] The WHI, a randomized, controlled trial of about 160,000 postmenopausal women, investigated the risks and benefits of HRT. The estrogen-plus-progestin arm of the study, in which more than 16,000 women were randomly assigned to receive combined estrogen and progestin or placebo, was halted early because health risks exceeded health benefits.[41,42] Significant increases in both total breast cancer cases (245 in the estrogen-plus-progestin group vs. 185 in the placebo group) and invasive breast cancer cases (199 in the estrogen-plus-progestin group vs. 150 in the placebo group) prompted early closure of the study (RR, 1.24; 95% CI, 1.02–1.5; P < .001). Risks for coronary heart disease, stroke, and pulmonary embolism also increased in the estrogen-plus-progestin group. The WHI study did not stratify data by participants' family histories of breast cancer, and subjects were not systematically tested for BRCA1/BRCA2 pathogenic variants.[42] Similar findings were seen in the estrogen-progestin arm of the prospective, observational Million Women’s Study in the United Kingdom.[43] However, breast cancer risk was not elevated in women randomly assigned to the estrogen-only group when compared with those in the placebo group in the WHI study (RR, 0.77; 95% CI, 0.59–1.01). Hysterectomy was required for women to qualify for the estrogen-only arm of this study; 40% of these patients also had a bilateral oophorectomy, which can potentially decrease breast cancer risk.[44]

Among women with family histories of breast cancer, the associations between HRT and breast cancer risk have not been consistent. Some studies suggested risk was particularly elevated among women with family histories of breast cancer, while others did not report an interaction between these factors.[45-49,39] A large meta-analysis found that women who used HRT had increased breast cancer risk. However, risk did not differ significantly between subjects with or without family histories of cancer.[49]

The effect of HRT on breast cancer risk among carriers of BRCA1 and BRCA2 pathogenic variants has been studied in the context of bilateral risk-reducing oophorectomy. Short-term HRT use does not seem to alter an oophorectomy's protective effect on breast cancer risk.[50] For example, a prospective, longitudinal cohort study recruited BRCA1 carriers from 80 centers in 17 countries. This study found that HRT use after oophorectomy was not associated with increased breast cancer risk in BRCA1 carriers.[51] The HR was 0.97 (95% CI, 0.62–1.52) for individuals who used HRT when compared with individuals who had never used HRT. However, the effects of estrogen-only HRT and estrogen-plus-progesterone HRT differed. After a 10-year follow-up period, the cumulative breast cancer incidence was 12% in women who used estrogen-only HRT and 22% in women who used estrogen-plus-progesterone HRT. These associations were stronger for women who underwent oophorectomy before age 45 years. The study concluded that using estrogen-only HRT after oophorectomy did not increase risk of BRCA1-associated breast cancers. However, the potential harmful effects of progesterone-containing HRT warrant further study.[52] For more information, see the HRT in Carriers of BRCA1/BRCA2 Pathogenic Variants section in BRCA1 and BRCA2: Cancer Risks and Management.

HRT use may also increase a woman's chance of developing endometrial cancer. For more information, see the Hormones section.

Radiation exposure

Radiation exposure can increase an individual's breast cancer risk. This is demonstrated by the survivors of the atomic bombings in Hiroshima and Nagasaki and by women who have received therapeutic radiation treatments to the chest and upper body. However, it is unclear how much radiation exposure affects breast cancer risk in women with high breast cancer susceptibility.

Early data suggested that carriers of BRCA1 and BRCA2 pathogenic variants may have increased sensitivity to radiation, which may contribute to cancer susceptibility.[53-56] Studies have shown that individuals with germline ATM and TP53 variants also have increased sensitivity to radiation.[57,58]

It is possible that radiation exposure from diagnostic procedures, including mammography, poses a greater risk to women with high breast cancer susceptibility than to women who are at average risk of developing breast cancer. Therapeutic radiation could also increase cancer risk in women with high breast cancer susceptibility. However, a cohort study of BRCA1 and BRCA2 pathogenic variant carriers treated with breast-conserving therapy did not show evidence of increased radiation sensitivity in participants. Sequelae were not observed in the breasts, lungs, or bone marrow of BRCA carriers.[59]

Conversely, tumors in women with pathogenic variants in breast cancer risk genes may be more responsive to radiation treatment than tumors in women at average breast cancer risk. Studies examining the impact of radiation exposure in carriers of BRCA1 and BRCA2 pathogenic variants have had conflicting results.[60-65] A large European study showed a dose-response relationship, in which breast cancer risk increased with total radiation exposure. However, this occurred most often when patients had nonmammographic radiation exposure before age 20 years.[64] A significant association was not observed between prior mammography exposure and breast cancer risk in a prospective study of 1,844 BRCA1 carriers and 502 BRCA2 carriers without breast cancer diagnoses upon study entry. The average follow-up period in this study was 5.3 years.[65]

A retrospective cohort study estimated the effect of adjuvant radiation therapy (for primary breast cancer) on CBC risk in BRCA1 and BRCA2 carriers (N, 691; median follow-up period, 8.6 y).[66] An association was not found between radiation therapy and CBC risk (HR, 0.82; 95% CI, 0.45–1.45). This was also true in patients who were younger than 40 years when they were diagnosed with their primary breast cancers (HR, 1.36; 95% CI, 0.60–3.09). A study examined the impact of radiation therapy on CBC risk in ATM, BRCA1/2, and CHEK2 1100delC carriers. CBC risk was not modified by radiation therapy, even though these women had a higher baseline risk of CBC than women in the general population (BRCA1/2 pathogenic variant carriers without radiation therapy: RR, 3.52; 95% CI, 1.76–7.01; BRCA1/2 pathogenic variant carriers with radiation therapy: RR, 4.46; 95% CI, 2.96–6.71).[67] Thus, it is important to differentiate individuals with increased CBC risk due to pathogenic variants from individuals with increased CBC risk due to radiation therapy. For more information, see the Mammography section in BRCA1 and BRCA2: Cancer Risks and Management.

Alcohol and smoking

The risk of breast cancer increases by approximately 10% for each 10 g of daily alcohol intake (approximately one drink or less) in the general population.[68,69] Prior studies of BRCA1/BRCA2 pathogenic variant carriers have not found an association between alcohol consumption and increased breast cancer risk.[70-72] The association between cigarette smoking and breast cancer risk in women with BRCA1/2 pathogenic variants is inconclusive.[73,74]

Recent studies have evaluated the association between alcohol consumption, tobacco smoking, and breast cancer risk in individuals with BRCA1/2 pathogenic variants or family histories of breast cancer. One study evaluated if tobacco smoking and alcohol consumption are associated with increased breast cancer risk in BRCA1 and BRCA2 carriers using pooled data from an international cohort.[75] This study did not find an association between alcohol consumption and increased breast cancer risk in BRCA1 and BRCA2 carriers. Parous BRCA carriers who smoked for more than 5 years before their first full-term pregnancy had a significantly increased breast cancer risk when compared with parous BRCA carriers who did not smoke. A prospective study evaluating a cohort of women with family histories of breast cancer found that alcohol consumption was associated with an increased number of ER-positive breast cancers in women at the lowest quantile of absolute breast cancer risk (HR, 1.46; 95% CI, 1.07–1.99).[76] Cigarette smoking was also associated with increased breast cancer risk in those at the highest quantile of absolute breast cancer risk.

Physical activity

Increased physical activity has been associated with reduced breast cancer risk in most epidemiological studies. This risk reduction has also been seen in studies of female BRCA1 or BRCA2 pathogenic variant carriers. For example, one study reported a 38% reduction in premenopausal breast cancer risk from moderate physical activity (OR for the top quartile of physical activity compared with the lowest level, 0.62; 95% CI, 0.40–0.96).[77] This reduction in breast cancer risk has been seen in women with varying levels of breast cancer susceptibility, including women who have family histories of breast cancer but do not have known BRCA1 or BRCA2 pathogenic variants.[78]

Risk Factors for Ovarian Cancer

Refer to the PDQ summary on Ovarian, Fallopian Tube, and Primary Peritoneal Cancers Prevention for information about risk factors for ovarian cancer in the general population.

Age

Ovarian cancer incidence rises in a linear fashion from age 30 years to age 50 years and continues to increase, though at a slower rate, thereafter. Before age 30 years, the risk of developing epithelial ovarian cancer is remote, even in hereditary cancer families.[79]

Family history including inherited cancer genes

Although reproductive, demographic, and lifestyle factors affect risk of ovarian cancer, the single greatest ovarian cancer risk factor is a family history of the disease. A large meta-analysis of 15 published studies estimated an OR of 3.1 for the risk of ovarian cancer associated with at least one FDR with ovarian cancer.[80]

Reproductive history

Nulliparity is consistently associated with an increased risk of ovarian cancer, including among carriers of BRCA/BRCA2 pathogenic variants, yet a meta-analysis identified a risk reduction only in women with four or more live births.[30] Risk may also be increased among women who have used fertility drugs, especially those who remain nulligravid.[81,82] Several studies have reported a risk reduction in ovarian cancer after OC use in carriers of BRCA/BRCA2 pathogenic variants;[83-85] a risk reduction has also been shown after tubal ligation in BRCA1 carriers, with a statistically significant decreased risk of 22% to 80% after the procedure.[85,86] Breastfeeding for more than 12 months may also be associated with a reduction in ovarian cancer among carriers of BRCA1/BRCA2 pathogenic variants.[87] On the other hand, evidence is growing that the use of menopausal HRT is associated with an increased risk of ovarian cancer, particularly in long-time users and users of sequential estrogen-progesterone schedules.[88-91]

Surgical history

Bilateral tubal ligation and hysterectomy are associated with reduced ovarian cancer risk,[81,92,93] including in carriers of BRCA/BRCA2 pathogenic variants.[94] Ovarian cancer risk is reduced more than 90% in women with documented BRCA1 or BRCA2 pathogenic variants who chose risk-reducing salpingo-oophorectomy (RRSO). In this same population, risk-reducing oophorectomy also resulted in a nearly 50% reduction in the risk of subsequent breast cancer.[95,96] While some studies have shown more benefit for breast cancer reduction in patients with BRCA2 versus BRCA1 pathogenic variants, others have shown no benefit for BRCA1 carriers. Additionally, many of the studies remain underpowered to demonstrate benefit.[97] (Refer to the Risk-reducing salpingo-oophorectomy for breast cancer risk reduction section in BRCA1 and BRCA2: Cancer Risks and Management for more information about these studies.)

Oral contraceptives (OCs)

Use of OCs for 4 or more years is associated with an approximately 50% reduction in ovarian cancer risk in the general population.[81,98] A majority of, but not all, studies also support OCs being protective among carriers of BRCA/BRCA2 pathogenic variants.[86,99-102] A meta-analysis of 18 studies including 13,627 carriers of BRCA pathogenic variants reported a significantly reduced risk of ovarian cancer (SRR, 0.50; 95% CI, 0.33–0.75) associated with OC use.[34] (Refer to the Chemopreventive agents for reducing ovarian cancer risk section in BRCA1 and BRCA2: Cancer Risks and Management.)

Risk Factors for Endometrial Cancer

Refer to the PDQ summary on Endometrial Cancer Prevention for information about risk factors for endometrial cancer in the general population.

Age

Age is an important risk factor for endometrial cancer. Most women with endometrial cancer are diagnosed after menopause. Only 15% of women are diagnosed with endometrial cancer before age 50 years, and fewer than 5% are diagnosed before age 40 years.[103] Women with Lynch syndrome tend to develop endometrial cancer at an earlier age, with the median age at diagnosis of 48 years.[104]

Family history including inherited cancer genes

Although the hyperestrogenic state is the most common predisposing factor for endometrial cancer, family history also plays a significant role in a woman’s risk for disease. Approximately 3% to 5% of uterine cancer cases are attributable to a hereditary cause,[105] with the main hereditary endometrial cancer syndrome being Lynch syndrome, an autosomal dominant genetic condition with a population prevalence of 1 in 300 to 1 in 1,000 individuals.[106,107] (Refer to the Lynch Syndrome section in Genetics of Colorectal Cancer for more information.)

Non-Lynch syndrome genes may also contribute to endometrial cancer risk. In an unselected endometrial cancer cohort undergoing multigene panel testing, approximately 3% of patients tested positive for a germline pathogenic variant in non-Lynch syndrome genes, including CHEK2, APC, ATM, BARD1, BRCA1, BRCA2, BRIP1, NBN, PTEN, and RAD51C.[108] Notably, patients with pathogenic variants in non-Lynch syndrome genes were more likely to have serous tumor histology than were patients without pathogenic variants. Furthermore, although the overall risk of endometrial cancer after RRSO was not increased among carriers of BRCA1 pathogenic variants, these patients seemed to have an increased risk of serous and serous-like endometrial cancer.[109] These findings were supported by a Dutch multicenter cohort study in women with germline BRCA1 and BRCA2 pathogenic variants. This study concluded that participants' AR for endometrial cancer was approximately 3%. Because some serous and p53-aberrant endometrial cancers may harbor germline or somatic BRCA1/BRCA2 variants, poly (ADP-ribose) polymerase (PARP) inhibitor therapy may also be a therapeutic option.[110]

Reproductive history

Reproductive factors such as multiparity, late menarche, and early menopause decrease the risk of endometrial cancer because of the lower cumulative exposure to estrogen and the higher relative exposure to progesterone.[111,112]

Hormones

Hormonal factors that increase the risk of type I endometrial cancer are better understood. All endometrial cancers share a predominance of estrogen relative to progesterone. Prolonged exposure to estrogen or unopposed estrogen increases the risk of endometrial cancer. Endogenous exposure to estrogen can result from obesity, polycystic ovary syndrome, and nulliparity, while exogenous estrogen can result from taking unopposed estrogen or tamoxifen. Unopposed estrogen increases the risk of developing endometrial cancer by twofold to twentyfold, proportional to the duration of use.[113,114] Tamoxifen, a selective estrogen receptor modulator, acts as an estrogen agonist on the endometrium while acting as an estrogen antagonist in breast tissue, and increases the risk of endometrial cancer.[115] In contrast, OCs, the LNG-IUS, and combination estrogen-progesterone HRT all reduce the risk of endometrial cancer through the antiproliferative effect of progesterone acting on the endometrium.[116-119]

Autosomal Dominant Inheritance of Breast and Gynecologic Cancer Predisposition

Autosomal dominant inheritance of breast and gynecologic cancers is characterized by transmission of cancer predisposition from generation to generation, through either the mother’s or the father’s side of the family, with the following characteristics:

Inheritance risk of 50%. When a parent carries an autosomal dominant genetic predisposition, each child has a 50:50 chance of inheriting the predisposition. Although the risk of inheriting the predisposition is 50%, not everyone with the predisposition will develop cancer because of incomplete penetrance and/or gender-restricted or gender-related expression.

Both males and females can inherit and transmit an autosomal dominant cancer predisposition. A male who inherits a cancer predisposition can still pass the altered gene on to his sons and daughters.

Breast and ovarian cancer are components of several autosomal dominant cancer syndromes. The syndromes most strongly associated with both cancers are the syndromes associated with BRCA1 or BRCA2 pathogenic variants. Breast cancer is also a common feature of Li-Fraumeni syndrome due to TP53 pathogenic variants and of PTEN hamartoma tumor syndromes (including Cowden syndrome) due to PTEN pathogenic variants.[120] Other genetic syndromes that may include breast cancer as an associated feature include heterozygous carriers of the ATM gene and Peutz-Jeghers syndrome. Ovarian cancer has also been associated with Lynch syndrome, basal cell nevus (Gorlin) syndrome, and multiple endocrine neoplasia type 1.[120] Lynch syndrome is mainly associated with colorectal cancer and endometrial cancer, although several studies have demonstrated that patients with Lynch syndrome are also at risk of developing transitional cell carcinoma of the ureters and renal pelvis; cancers of the stomach, small intestine, liver and biliary tract, brain, breast, prostate, and adrenal cortex; and sebaceous skin tumors (Muir-Torre syndrome).[121-127]

Germline pathogenic variants in the genes responsible for these autosomal dominant cancer syndromes produce different clinical phenotypes of characteristic malignancies and, in some instances, associated nonmalignant abnormalities.

The family characteristics that suggest hereditary cancer predisposition include the following:

Multiple cancers within a family.

Cancers typically occur at an earlier age than in sporadic cases (defined as cases not associated with genetic risk).

Two or more primary cancers in a single individual. These could be multiple primary cancers of the same type (e.g., bilateral breast cancer) or primary cancer of different types (e.g., breast cancer and ovarian cancer in the same individual or endometrial and colon cancer in the same individual).

Cases of male breast cancer. The inheritance risk for autosomal dominant genetic conditions is 50% for both males and females, but the differing penetrance of the genes may result in some unaffected individuals in the family.

Figure 1 and Figure 2 depict some of the classic inheritance features of a BRCA1 and BRCA2 pathogenic variant, respectively. Figure 3 depicts a classic family with Lynch syndrome. For more information about pedigree nomenclature, see the Family history section in Cancer Genetics Risk Assessment and Counseling.

There are no pathognomonic features distinguishing breast and ovarian cancers occurring in carriers of BRCA1 or BRCA2 pathogenic variants from those occurring in noncarriers. Breast cancers occurring in carriers of BRCA1 pathogenic variants are more likely to be ER-negative, progesterone receptor (PR)–negative, human epidermal growth factor receptor two (HER2/neu)–negative (i.e., triple-negative breast cancers [TNBC]), and have a basal phenotype. BRCA1-associated ovarian cancers are more likely to be high-grade and of serous histopathology. (Refer to the BRCA1/2-associated breast cancer pathology and Pathologies of BRCA1/2-associated ovarian, fallopian tube, and primary peritoneal cancers sections in BRCA1 and BRCA2: Cancer Risks and Management for more information.)

Some pathologic features distinguish carriers of Lynch syndrome–associated pathogenic variants from noncarriers. The hallmark feature of endometrial cancers occurring in Lynch syndrome is mismatch repair (MMR) deficiencies, including the presence of microsatellite instability (MSI), and the absence of specific MMR proteins. In addition to these molecular changes, there are also histologic changes including tumor-infiltrating lymphocytes, peritumoral lymphocytes, undifferentiated tumor histology, lower uterine segment origin, and synchronous tumors.

Considerations in Risk Assessment and in Identifying a Family History of Breast and Ovarian Cancer Risk

The accuracy and completeness of family histories must be considered when they are used to assess risk. A reported family history may be erroneous, or a person may be unaware of relatives affected with cancer. In addition, small family sizes and premature deaths may limit the information obtained from a family history. Breast or ovarian cancer on the paternal side of the family usually involves more distant relatives than does breast or ovarian cancer on the maternal side, so information may be more difficult to obtain. When self-reported information is compared with independently verified cases, the sensitivity of a history of breast cancer is relatively high, at 83% to 97%, but lower for ovarian cancer, at 60%.[128,129] Additional limitations of relying on family histories include adoption; families with a small number of women; limited access to family history information; and incidental removal of the uterus, ovaries, and/or fallopian tubes for noncancer indications. Family histories will evolve; therefore, it is important to update family histories from both parents over time. (Refer to the Accuracy of the family history section in Cancer Genetics Risk Assessment and Counseling for more information.)

Models for Prediction of Breast and Gynecologic Cancer Risk

Models to predict an individual’s lifetime risk of developing breast and/or gynecologic cancer are available.[130-133] In addition, models exist to predict an individual’s likelihood of having a pathogenic variant in BRCA1, BRCA2, or one of the MMR genes associated with Lynch syndrome. (Refer to the Models for prediction of the likelihood of a BRCA1 or BRCA2 pathogenic variant section of this summary for more information about some of these models.) Not all models can be appropriately applied to all patients. Each model is appropriate only when the patient’s characteristics and family history are similar to those of the study population on which the model was based. Different models may provide widely varying risk estimates for the same clinical scenario, and the validation of these estimates has not been performed for many models.[131,134,135]

Breast cancer risk assessment models

In general, breast cancer risk assessment models are designed for two types of populations: 1) women without a pathogenic variant or strong family history of breast or ovarian cancer; and 2) women at higher risk because of a personal or family history of breast cancer or ovarian cancer.[135] Models designed for women of the first type (e.g., the Gail model, which is the basis for the Breast Cancer Risk Assessment Tool [BCRAT] [136], and the Colditz and Rosner model [137]) require only limited information about family history (e.g., number of FDRs with breast cancer). Models designed for women at higher risk require more detailed information about personal and family cancer history of breast and ovarian cancers, including ages at onset of cancer and/or carrier status of specific breast cancer-susceptibility alleles. The genetic factors used by the latter models differ, with some assuming one risk locus (e.g., the Claus model [138]), others assuming two loci (e.g., the International Breast Cancer Intervention Study [IBIS] model [139] and the BRCAPRO model [140]), and still others assuming an additional polygenic component in addition to multiple loci (e.g., the Breast and Ovarian Analysis of Disease Incidence and Carrier Estimation Algorithm [BOADICEA] model [141-143]). The models also differ in whether they include information about nongenetic risk factors. Three models (Gail/BCRAT, Pfeiffer,[133] and IBIS) include nongenetic risk factors but differ in the risk factors they include (e.g., the Pfeiffer model includes alcohol consumption, whereas the Gail/BCRAT does not). These models have limited ability to discriminate between individuals who are affected and those who are unaffected with cancer; a model with high discrimination would be close to 1, and a model with little discrimination would be close to 0.5; the discrimination of the models currently ranges between 0.56 and 0.63).[144] The existing models generally are more accurate in prospective studies that have assessed how well they predict future cancers.[135,145-147] An analysis comparing the 10-year performance of the BOADICEA, BRCAPRO, BCRAT, and IBIS models demonstrated superiority of the models with more detailed pedigree inclusion—specifically, BOADICEA and IBIS.[148]

In the United States, BRCAPRO, the Claus model,[138,149] and the Gail/BCRAT [136] are widely used in clinical counseling. Risk estimates derived from the models differ for an individual patient. Several other models that include more detailed family history information are also in use and are discussed below.

Additional considerations for clinical use of breast cancer risk assessment models

The Gail model is the basis for the BCRAT, a computer program available from the National Cancer Institute by calling the Cancer Information Service at 1-800-4-CANCER (1-800-422-6237). This version of the Gail model estimates only the risk of invasive breast cancer. The Gail/BCRAT model has been found to be reasonably accurate at predicting breast cancer risk in large groups of White women who undergo annual screening mammography; however, reliability varies depending on the cohort studied.[150-155] Risk can be overestimated in the following populations:

Women who do not adhere to screening recommendations.[150,151]

Women in the highest-risk strata.[153]

The Gail/BCRAT model is valid for women aged 35 years and older. The model was primarily developed for White women.[154] Extensions of the Gail model for African American women have been subsequently developed to calibrate risk estimates using data from more than 1,600 African American women with invasive breast cancer and more than 1,600 controls.[156] Additionally, extensions of the Gail model have incorporated high-risk single nucleotide variants (SNVs) and pathogenic variants; however, no software exists to calculate risk in these extended models.[157,158] Other risk assessment models incorporating breast density have been developed but are not ready for clinical use.[159,160]

Generally, the Gail/BCRAT model should not be the sole model used for families with one or more of the following characteristics:

Multiple affected individuals with breast cancer or ovarian cancer (especially when one or more breast cancers are diagnosed before age 50 y).

A woman with both breast and ovarian cancer.

Ashkenazi Jewish ancestry with at least one case of breast or ovarian cancer (as these families are more likely to have a hereditary cancer susceptibility syndrome).

Commonly used models that incorporate family history include the IBIS, BOADICEA, and BRCAPRO models. The IBIS/Tyrer-Cuzick model incorporates both genetic and nongenetic factors.[139] A three-generation pedigree is used to estimate the likelihood that an individual carries either a BRCA1/BRCA2 pathogenic variant or a hypothetical low-penetrance gene. In addition, the model incorporates personal risk factors such as parity, body mass index (BMI); height; and age at menarche, first live birth, menopause, and HRT use. Both genetic and nongenetic factors are combined to develop a risk estimate. The BOADICEA model examines family history to estimate breast cancer risk and also incorporates both BRCA1/BRCA2 and non-BRCA1/BRCA2 genetic risk factors.[142] The most important difference between BOADICEA and the other models using information on BRCA1/BRCA2 is that BOADICEA assumes an additional polygenic component in addition to multiple loci,[141-143] which is more in line with what is known about the underlying genetics of breast cancer. The BOADICEA model has also been expanded to include additional pathogenic variants, including CHEK2, ATM, and PALB2.[161] However, the discrimination and calibration for these models differ significantly when compared in independent samples;[145] the IBIS and BOADICEA models are more comparable when estimating risk over a shorter fixed time horizon (e.g., 10 years),[145] than when estimating remaining lifetime risk. As all risk assessment models for cancers are typically validated over a shorter time horizon (e.g., 5 or 10 years), fixed time horizon estimates rather than remaining lifetime risk may be more accurate and useful measures to convey in a clinical setting.

In addition, readily available models that provide information about an individual woman’s risk in relation to the population-level risk depending on her risk factors may be useful in a clinical setting (e.g., Your Disease Risk). Although this tool was developed using information about average-risk women and does not calculate AR estimates, it still may be useful when counseling women about cancer prevention. Risk assessment models are being developed and validated in large cohorts to integrate genetic and nongenetic data, breast density, and other biomarkers.

Although most breast cancer risk models have been shown to be well calibrated overall, model performance can be different for subgroups of women. In particular, independent, prospective validation of risk models for women who tested negative for BRCA1 or BRCA2 pathogenic variants supported that the most commonly used clinical risk models underpredicted risk for this group of women.[162] The performance also differed on the basis of whether the test results of relatives were known. The models also underpredicted risk by 26.3% to 56.7% in women who tested negative but whose relatives had not been tested.

Ovarian cancer risk assessment models

Two risk prediction models have been developed for ovarian cancer.[132,133] The Rosner model [132] included age at menopause, age at menarche, oral contraception use, and tubal ligation; the concordance statistic was 0.60 (0.57–0.62). The Pfeiffer model [133] included oral contraceptive use, menopausal HRT use, and family history of breast cancer or ovarian cancer, with a similar discriminatory power of 0.59 (0.56–0.62). Although both models were well calibrated, their modest discriminatory power limited their screening potential.

Endometrial cancer risk assessment models

The Pfeiffer model has been used to predict endometrial cancer risk in the general population.[133] For endometrial cancer, the RR model included BMI, menopausal HRT use, menopausal status, age at menopause, smoking status, and OC use. The discriminatory power of the model was 0.68 (0.66–0.70); it overestimated observed endometrial cancers in most subgroups but underestimated disease in women with the highest BMI category, in premenopausal women, and in women taking menopausal HRT for 10 years or more.

In contrast, MMRpredict, PREMM5 (PREdiction Model for gene Mutations), and MMRpro are three quantitative predictive models used to identify individuals who may potentially have Lynch syndrome.[163-165] MMRpredict incorporates only colorectal cancer patients but does include MSI and immunohistochemistry (IHC) tumor testing results. PREMM5 is an update of PREMM (1,2,6) and includes each of the five genes associated with Lynch syndrome, including PMS2 and EPCAM. It accounts for other Lynch syndrome–associated tumors but does not include tumor testing results.[164] MMRpro incorporates tumor testing and germline testing results, but is more time intensive because it includes affected and unaffected individuals in the risk-quantification process. All three predictive models are comparable to the traditional Amsterdam and Bethesda criteria in identifying individuals with colorectal cancer who carry MMR gene pathogenic variants.[166] However, because these models were developed and validated in colorectal cancer patients, the discriminative abilities of these models to identify Lynch syndrome are lower among individuals with endometrial cancer than among those with colon cancer.[167] In fact, the sensitivity and specificity of MSI and IHC in identifying carriers of pathogenic variants are considerably higher than the prediction models and support the use of molecular tumor testing to screen for Lynch syndrome in women with endometrial cancer.

Table 1 summarizes salient aspects of breast and gynecologic cancer risk assessment models that are commonly used in the clinical setting. These models differ by the extent of family history included, whether nongenetic risk factors are included, and whether carrier status and polygenic risk are included (inputs to the models). The models also differ in the type of risk estimates that are generated (outputs of the models). These factors may be relevant in choosing the model that best applies to a particular individual.

Table 1. Summary of Prediction Models Used to Calculate Age-Specific Absolute Risks of Breast and Gynecologic CancersModel Family History (input) Pathogenic Variants (input) Risk Factors (input) Risk Estimate Generated (output)Breast Cancer Risk Assessment ModelsModels for Average-Risk WomenGail/BCRAT First-degree relatives (breast cancer)NoYesBreast cancerPfeiffer (breast) [133]First-degree relatives (breast, ovarian cancers)NoYesBreast cancerColditz and Rosner [137]NoneNoYesBreast cancerModels for High-Risk WomenaClaus [138]Multigenerational (breast cancer)NoNoBreast cancer BRCAPRO Multigenerational (breast, ovarian cancers)BRCA1/BRCA2 NoBreast cancer; % risk of carrying BRCA1/BRCA2 pathogenic variantIBIS Multigenerational (ovarian cancer)BRCA1/BRCA2 YesBreast cancer; % risk of carrying BRCA1/BRCA2 pathogenic variantBOADICEA (CanRisk tool)b Multigenerational (pancreatic, breast, ovarian cancers)BRCA1/BRCA2 NoBreast and ovarian cancer; % risk of carrying BRCA1/BRCA2 pathogenic variantOvarian Cancer Risk Assessment ModelsModels for Average-Risk WomenRosner [132]None NoYesOvarian cancer Pfeiffer (ovarian) [133]First-degree relatives (breast, ovarian cancers)NoYesBreast cancer Models for High-Risk Womena BOADICEA (CanRisk tool)b Multigenerational (pancreatic, breast, ovarian cancers)BRCA1/BRCA2 NoBreast and ovarian cancer; % risk of carrying BRCA1/BRCA2 pathogenic variantEndometrial Cancer Risk Assessment ModelsModels for Average-Risk WomenPfeiffer (endometrial) [133] NoneNoYesEndometrial cancerModels for High-Risk WomenaPREMM5Multigenerational (colon, endometrial and other Lynch syndrome–associated cancers and polyps)NoNo% risk of carrying MLH1, MSH2, MSH6 pathogenic variantMMRproMultigenerational (colon, endometrial cancers)NoNo% risk of carrying MLH1, MSH2, MSH6 pathogenic variantMMRpredict [163]Multigenerational (colon, endometrial cancers)NoNo% risk of carrying MLH1, MSH2, MSH6 pathogenic variant

Models for Predicting the Likelihood of a BRCA1/BRCA2 Pathogenic Variant

Many models have been developed to predict the probability of identifying germline BRCA1/BRCA2 pathogenic variants in individuals or families. These models include those using logistic regression,[140,168-173] genetic models using Bayesian analysis (BRCAPRO and BOADICEA),[140,142] and empiric observations.[174-179]

In addition to BOADICEA, BRCAPRO is commonly used for genetic counseling in the clinical setting. BRCAPRO and BOADICEA predict the probability of being a carrier and produce estimates of breast cancer risk (refer to Table 2). The discrimination and accuracy (factors used to evaluate the performance of prediction models) of these models are much higher for their ability to report on carrier status than for their ability to predict fixed or remaining lifetime risk.

BOADICEA is a polygenetic model that uses complex segregation analysis to examine both breast cancer risk and the probability of having a BRCA1 or BRCA2 pathogenic variant.[142] Even among experienced providers, the use of prediction models has been shown to increase the power to discriminate which patients are most likely to be carriers of BRCA1/BRCA2 pathogenic variants.[180,181] Most models do not include other cancers seen in the BRCA1 and BRCA2 spectrum, such as pancreatic cancer and prostate cancer. Interventions that decrease the likelihood that an individual will develop cancer (such as oophorectomy and mastectomy) may influence the ability to predict BRCA1 and BRCA2 pathogenic variant status.[182] One study has shown that the prediction models for genetic risk are sensitive to the amount of family history data available and do not perform as well with limited family information.[183] BOADICEA is being expanded to incorporate additional risk variants (genome-wide association studies [GWAS] and SNVs) to better predict pathogenic variant status and to improve the accuracy of breast cancer and ovarian cancer risk estimates.[184]

The performance of the models can vary in specific ethnic groups. The BRCAPRO model appeared to best fit a series of French Canadian families.[185] There have been variable results in the performance of the BRCAPRO model among Hispanic individuals,[186,187] and both the BRCAPRO model and Myriad tables underestimated the proportion of carriers of pathogenic variants in an Asian American population.[188] BOADICEA was developed and validated in British women. Thus, the major models used for both overall risk (Table 1) and genetic risk (Table 2) have not been developed or validated in large populations of racially and ethnically diverse women. Of the commonly used clinical models for assessing genetic risk, only the Tyrer-Cuzick model contains nongenetic risk factors.

The power of several of the models has been compared in different studies.[189-192] Four breast cancer genetic-risk models, BOADICEA, BRCAPRO, IBIS, and eCLAUS, were evaluated for their diagnostic accuracy in predicting BRCA1/BRCA2 pathogenic variants in a cohort of 7,352 German families.[193] The family member with the highest likelihood of carrying a pathogenic variant from each family was screened for BRCA1/BRCA2 pathogenic variants. Carrier probabilities from each model were calculated and compared with the actual variants detected. BRCAPRO and BOADICEA had significantly higher diagnostic accuracy than IBIS or eCLAUS. Accuracy for the BOADICEA model was further improved when statuses of the tumor markers ER, PR, and HER2/neu were included in the model. The inclusion of these biomarkers has been shown to improve the performance of BRCAPRO.[194,195]

Table 2. Characteristics of Common Models for Estimating the Likelihood of a BRCA1/BRCA2 Pathogenic VariantMyriad Prevalence Tables [170]BRCAPRO [140,182]BOADICEA [140,142]Tyrer-Cuzick [139]MethodEmpiric data from Myriad Genetics based on personal and family history reported on requisition formsStatistical model, assumes autosomal dominant inheritanceStatistical model, assumes polygenic riskStatistical model, assumes autosomal dominant inheritanceFeatures of the modelProband may or may not have breast or ovarian cancer Proband may or may not have breast or ovarian cancerProband may or may not have breast or ovarian cancerProband must be unaffected Considers age of breast cancer diagnosis as <50 y, >50 y Considers exact age at breast and ovarian cancer diagnosis Considers exact age at breast and ovarian cancer diagnosis Also includes reproductive factors and body mass index to estimate breast cancer risk Considers breast cancer in ≥1 affected relative only if diagnosed <50 y Considers prior genetic testing in family (i.e., BRCA1/BRCA2 pathogenic variant–negative relatives) Includes all FDR and SDR with and without cancer Considers ovarian cancer in ≥1 relative at any age Considers oophorectomy status Includes AJ ancestry Includes AJ ancestry Includes all FDR and SDR with and without cancer Very easy to use Includes AJ ancestry LimitationsSimplified/limited consideration of family structureRequires computer software and time-consuming data entry Requires computer software and time-consuming data entryDesigned for individuals unaffected with breast cancer Incorporates only FDR and SDR; may need to change proband to best capture risk and to account for disease in the paternal lineage May overestimate risk in bilateral breast cancer [196] Early age of breast cancer onset May perform better in White populations than in racial and ethnic minority populations [187,197] Incorporates only FDR and SDR; may need to change proband to best capture risk May underestimate risk of BRCA pathogenic variant in high-grade serous ovarian cancers but overestimate the risk for other histologies [198]

Genetic testing for BRCA1 and BRCA2 pathogenic variants has been available to the public since 1996. As more individuals have undergone testing, risk assessment models have improved. This, in turn, gives providers better data to estimate an individual patient’s risk of carrying a pathogenic variant, but risk assessment continues to be an art. There are factors that might limit the ability to provide an accurate risk assessment (i.e., small family size, paucity of women, or ethnicity) including the specific circumstances of the individual patient (such as history of disease or risk-reducing surgeries).

Considerations When Conducting Genetic Testing

Indications for hereditary breast and gynecologic cancers genetic testing

Several professional organizations and expert panels—including the American Society of Clinical Oncology,[199] the National Comprehensive Cancer Network (NCCN),[200] the American Society of Human Genetics,[201] the American College of Medical Genetics and Genomics,[202] the National Society of Genetic Counselors,[202] the U.S. Preventive Services Task Force,[203] and the Society of Gynecologic Oncologists [204] —have developed clinical criteria and practice guidelines that can be helpful to health care providers in identifying individuals who may have a BRCA1 or BRCA2 pathogenic variant.

In 2019, the American Society of Breast Surgeons published a recommendation to make genetic testing for “BRCA1/BRCA2, and PALB2, with other genes as appropriate for the clinical scenario and family history” available to all breast cancer patients.[205] This recommendation was based on a study that suggested similar pathogenic variant rates identified through an extended multigene panel in patients with breast cancer who did or did not meet the NCCN guidelines for genetic testing.[206] This study had important methodologic challenges that need to be considered, including exclusion of participants previously tested, uncertain accuracy of the reported risk criteria for study participants, inclusion of genes with uncertain management guidelines, and difference in the specific genes in which pathogenic or likely pathogenic variants were identified across the two groups. For example, there was a statistically significant difference between participants who met and who did not meet NCCN criteria in the detection of BRCA1/BRCA2 variants.

Other studies have also found that the NCCN criteria have good sensitivity when predicting BRCA1/BRCA2 variants; however, less is known about many other genes. For example, one study showed that the NCCN criteria were able to detect 88.9% of the BRCA1/BRCA2 pathogenic variant carriers [207] and others have found that, if more than one NCCN criterion is met, then the positive predictive value does pass the 10% threshold (e.g., 12% for more than two NCCN criteria).[208]

As the cost of genetic testing continues to decrease, there is a need for unbiased evidence to guide indications for testing, including the cost-benefit impact on screening, prevention, and treatment. Efforts to generate less biased evidence include a single institution study of 3,907 unselected women with breast cancer tested for nine breast cancer genes, including BRCA1/BRCA2, ATM, CDH1, CHEK2, NF1, PALB2, PTEN, and TP53.[209] The study assessed the relative performance of NCCN genetic testing criteria as compared with the American Society of Breast Surgeons' recommendation to test all women aged 65 years or younger with breast cancer. The sensitivity of the criteria was defined as the proportion of individuals who met testing criteria and tested positive for a pathogenic or likely pathogenic variant of the total population of pathogenic or likely pathogenic variant carriers in the study, while the specificity was defined as the proportion of individuals who did not meet testing criteria and tested negative for a pathogenic or likely pathogenic variant of the total population of noncarriers in the study. High sensitivity and specificity are both important considerations; however, higher sensitivity leads to lower specificity, so it is important to balance these two factors. Detection of BRCA1/BRCA2 pathogenic or likely pathogenic variants based on NCCN criteria had a sensitivity of 87% with a specificity of 53.5%; when expanded to the nine genes included in the study, sensitivity was 70% and specificity was 53.2%. When including all women diagnosed with breast cancer at age 65 or younger, the sensitivity to detect BRCA1/BRCA2 pathogenic or likely pathogenic variants increased to 98%, while the specificity dropped to 22%. Among those who did not meet NCCN criteria, 0.7% had pathogenic or likely pathogenic BRCA1/BRCA2 variants.

Another study to assess frequency of pathogenic or likely pathogenic variants among breast cancer patients included a nested case-control study conducted through the WHI cohort among women with (cases) and without (controls) invasive breast cancer. Participants were tested for pathogenic or likely pathogenic variants in ten breast cancer–associated genes, including BRCA1/BRCA2.[210] The prevalence of pathogenic or likely pathogenic BRCA1/BRCA2 variants among those diagnosed with invasive breast cancer before age 65 years was 2.21%, compared with 1.09% among those diagnosed at age 65 years or older. In comparison, the frequency of pathogenic or likely pathogenic BRCA1/BRCA2 variants was 0.22% in the control group. Current genetic testing criteria detect BRCA pathogenic variants. Although higher sensitivity is always desired, it is at the expense of specificity. Lower specificity leads to higher costs to achieve one positive genetic test.

Benefits of offering genetic testing at the time of cancer diagnosis

At the time of a new cancer diagnosis, genetic testing for inherited cancer predisposition may guide patient care including decisions about surgery, chemotherapy and other biologics, and radiation treatment.[211,212] Among high-risk patients, the option of genetic testing is an important part of the shared decision-making process regarding cancer treatments at the time of diagnosis. Tools are available to facilitate decision making about genetic testing in this context.[213]

Breast cancer diagnosis

Benefits of offering genetic testing at the time of breast cancer diagnosis include, but are not limited to, the following:

Surgery: The identification of inherited susceptibility to breast cancer may influence surgical treatment decisions. As an example, the high risk of a second primary breast cancer among BRCA pathogenic variant carriers, particularly those diagnosed at an early age, may influence their decision to choose a bilateral mastectomy (versus a lumpectomy or unilateral/subtotal mastectomy) for surgical treatment of their breast cancer.[214] Discussion of RRSO is indicated,[215] and referral to a gynecologic provider may be considered.

Chemotherapy and other biologics: Medical treatments may be guided by the identification of a pathogenic variant in an inherited cancer predisposing gene. As an example, among BRCA pathogenic variant carriers, breast cancer treatment may include the use of platinum-based agents.[216] Furthermore, novel agents such as PARP inhibitors may be used in the treatment of metastatic breast cancer.[217]

Radiation therapy: Decisions about the use of radiation treatment may be guided by the presence of a pathogenic variant in an inherited breast cancer susceptibility gene. In particular, the poorer wound healing in irradiated breasts is an important consideration for those who may consider risk-reducing mastectomy with reconstruction. As an example, individuals with a pathogenic variant in TP53 may experience higher risks from radiation, including increased risks for subsequent new cancers.[218,219] Thus, identification of TP53 carriers in the context of an active breast cancer diagnosis may influence radiation treatment decisions and reconstruction options.

Ovarian cancer diagnosis

Benefits of offering genetic testing at the time of ovarian cancer diagnosis include, but are not limited to, the following:

Surgery: In most cases, the decision for ovarian cancer surgery is made on the basis of an adnexal mass or abdominal symptoms. When possible, considering the likelihood of a heritable genetic variant at the time of diagnosis may add value to surgical decision-making. The identification of inherited susceptibility to ovarian/fallopian tube cancer may influence surgical treatment decisions. For a questionable adnexal mass in a younger woman who is at risk of carrying a pathogenic variant of a highly penetrant ovarian cancer gene, knowledge of this information may help guide a decision for risk-reducing or therapeutic surgery.[220,221] For women who may be considering fertility preservation surgery, genetic knowledge may motivate consideration of bilateral salpingo-oophorectomy, and in the case of carriers of BRCA1 pathogenic variants, a more detailed discussion regarding aggressive uterine cancer risk.

Chemotherapy and other biologics: First-line chemotherapy for ovarian cancer still relies on a backbone of platinum and taxane chemotherapy. Current treatment options for optimally resected stage III ovarian carcinoma include intravenous (IV) chemotherapy, dose-dense IV chemotherapy, and a combination of IV paclitaxel plus intraperitoneal (IP) cisplatin, followed by IP paclitaxel 1 week later. Carriers of BRCA1 and BRCA2 pathogenic variants are considered more platinum sensitive, with longer progression-free survival times compared with BRCA1 and BRCA2 wild-type patients,[222,223] so it is unclear whether a particular treatment strategy is driven more by antiangiogenesis effects, peritoneal dose intensity, or platinum dose intensity. The advent of PARP as a biologic target (in combination with chemotherapy or as maintenance) may also increase the armory of first-line treatment of ovarian cancer.[224] (Refer to the Ovarian Cancer Treatment Strategies section in BRCA1 and BRCA2: Cancer Risks and Management for more information about PARP inhibitors in ovarian cancer treatment.)

Endometrial cancer diagnosis

Benefits of offering genetic testing at the time of endometrial cancer diagnosis include, but are not limited to, the following:

Surgery: The most common treatment for a newly diagnosed endometrial cancer includes hysterectomy with removal of the ovaries and fallopian tubes, as well as assessment of lymph nodes.[225] An exception to this practice might apply to a younger woman who wishes to retain fertility or retain her adnexa. IHC of endometrial sampling may allow for an assessment of the likelihood of a heritable genetic variant at the time of diagnosis, which may add value to the surgical decision-making process. For a young woman who is found to have Lynch syndrome, knowledge of this information may help guide a decision for hormonal management of endometrial cancer to allow future childbearing, or RRSO if her risk of ovarian cancer is deemed high enough on the basis of a specific genetic variant. For a young woman who is found to carry a pathogenic variant in BRCA1/BRCA2, or one of the other homologous recombination deficiencies increasing ovarian cancer risk, she may wish to decide between salpingo-oophorectomy or, at least, salpingectomy.

Chemotherapy and other biologics: Immune checkpoint inhibitors are now approved for use in endometrial cancers that have MSI or MMR deficiency.[226] While MSI and MMR status can be assessed at either the time of diagnosis or recurrent disease, it may be beneficial to perform tumor testing at diagnosis with the primary pathology processing, usually at the time of hysterectomy.

Multigene (panel) testing

Since the availability of next-generation sequencing and the Supreme Court of the United States ruling that human genes cannot be patented, several clinical laboratories now offer genetic testing through multigene panels at a cost comparable to that of single-gene testing. Even testing for BRCA1 and BRCA2 is a limited panel test of two genes. Approximately 25% of all ovarian/fallopian tube/peritoneal cancers are caused by a heritable genetic condition. Of these, about one-quarter (6% of all ovarian/fallopian tube/peritoneal cancers) are caused by genes other than BRCA1 and BRCA2, including many genes associated with the Fanconi anemia pathway or otherwise involved with homologous recombination.[227] In a population of ovarian cancer patients who test negative for BRCA1 and BRCA2 pathogenic variants, multigene panel testing can reveal actionable pathogenic variants.[228-230]

In general, multigene panel testing increases the yield of non-BRCA pathogenic variants across a variety of populations.[212,231-233] In an unselected population of breast cancer patients, the prevalence of BRCA1 and BRCA2 pathogenic variants was 6.1%, while the prevalence of pathogenic variants in other breast/ovarian cancer–predisposing genes was 4.6%.[234] In an unselected population of endometrial cancer patients, the prevalence of Lynch syndrome pathogenic variants (MLH1, MSH2, EPCAM-MSH2, MSH6, and PMS2) was 5.8%; the prevalence of pathogenic variants in other actionable genes was 3.4%.[108] Similarly, in a study of 35,409 women with breast cancer tested with the Myriad 25-gene panel, a pathogenic variant was found in 9.3% of women.[235] Among that 9.3%, 48.5% of the women carried a pathogenic variant in BRCA1 or BRCA2. The majority of other breast cancer genes with pathogenic variants identified included CHEK2 (11.7%), ATM (9.7%), and PALB2 (9.3%). The prevalence of pathogenic variants in the other breast cancer genes on the panel ranged from 0.05% to 0.31%. Pathogenic variants in Lynch syndrome genes accounted for 7.0% of variants identified; 3.7% were found in other genes included in the panel. The rate of pathogenic variants was higher in women with TNBC diagnosed before age 40 years. A similar trend of identifying pathogenic variants in non-BRCA susceptibility genes in male breast cancer patients has also been described.[236] In two studies of women who had previously tested negative for BRCA1/BRCA2, reflex testing with a multigene panel identified pathogenic variants in additional genes among 8% to 11% of cases.[237,238] In a study of 77,085 patients with breast cancer and 6,001 patients with ovarian cancer, 24.1% and 30.9% had genetic testing, respectively. Of those tested, pathogenic or likely pathogenic variants were identified in 7.8% of patients with breast cancer and 14.5% of patients with ovarian cancer. Prevalent non-BRCA pathogenic variants identified in patients with breast cancer included CHEK2 (1.6%), PALB2 (1.0%), ATM (0.7%), and NBN (0.4%). In patients with ovarian cancer, non-BRCA pathogenic variants included CHEK2 (1.4%), BRIP1 (0.9%), MSH2 (0.8%), and ATM (0.6%).[239] The potential utility of genetic testing in patients with ovarian tumors of all histologies was suggested in a study using a 32-gene panel that found 13.2% of 4,439 tumors harbored a pathogenic variant. Rates were highest among those with serous ovarian carcinoma (14.7%), although likely pathogenic variants were also seen in those with other histologies (borderline, germ cell, and sex cord stromal tumors), the significance of which is unclear to clinical management or etiology of disease.[240]

Multi-gene panel testing was conducted as part of two large efforts led by the worldwide Breast Cancer Association Consortium (BCAC) [241] and the United States–based CARRIERS consortium.[242] The BCAC study tested 113,927 women for 34 inherited cancer genes, while the CARRIERS study tested 64,791 women for 28 hereditary cancer genes. In both studies, significant associations were reported between eight genes and breast cancer development (BRCA1, BRCA2, PALB2, BARD1, RAD51C, RAD51D, ATM, and CHEK2). Associations were only reported between MSH6 and breast cancer development in the BCAC study. Similarly, associations were only reported between CDH1 and breast cancer development in the CARRIERS study. Both TP53 and PTEN (which are established breast cancer risk genes that are linked to early-onset disease) were not significantly associated with breast cancer development in these studies. This is presumably because TP53 and PTEN pathogenic variants are very rare.

NCCN recommends that women diagnosed with TNBC undergo BRCA1/BRCA2, CDH1, PALB2, PTEN, STK11, and TP53 testing to guide treatment decisions at any age.[200] A large study utilizing multigene (panel) testing comprising two separate cohorts reported that, in addition to BRCA1/BRCA2 genes, six other breast cancer susceptibility genes were also related to a higher risk of TNBC. Specifically, pathogenic variants in BARD1, PALB2, and RAD51D, in addition to BRCA1 and BRCA2, were each associated with more than a fivefold increase in breast cancer.[243] Pathogenic variants in three other genes —BRIP1, RAD51C, and TP53— were each associated with an increased TNBC risk of more than twofold. Pathogenic variants in these eight genes were reported in 12% of the TNBC cases (8.3% BRCA1/BRCA2, 3.7% non-BRCA1/BRCA2). The study was conducted in a clinical testing cohort of 140,449 individuals (8,753 TNBC cases) who received genetic testing using a 21-gene panel (sample A). In addition, a second sample (sample B) examined gene frequency rates in a pooled consortium of 2,143 individuals using a 17-gene panel. The overall frequency of pathogenic variants in the 21 genes examined in sample A was 14.4% (8.4% BRCA1/BRCA2, 6.0% non-BRCA1/BRCA2). The two samples had very consistent findings with respect to the risk estimates despite differences in age, race, ethnicity, and family history of cancer with sample A being younger, more racially and ethnically diverse, and more likely to have a family history of cancer. The pathogenic variant frequency detection in these 21 genes was also similar for White individuals (14% overall, 7.8% BRCA1/BRCA2, 6.2% non-BRCA1/BRCA2) and African American individuals (14.6% overall, 9.0% BRCA1/BRCA2, 5.6% non-BRCA1/BRCA2).

Multi-gene panel testing studies were conducted in women from the United States who had African ancestry, and results showed that certain genes were associated with increased breast cancer risk in this population. These genes were similar to the breast cancer risk genes found in individuals from the United States with European ancestry. A case-control study of 10,047 women with African ancestry found a pathogenic variant frequency of 10.3% in those with ER-negative breast cancer, 5.2% in those with ER-positive breast cancer, and 2.3% in those without breast cancer. BRCA1 (OR, 47), BRCA2 (OR, 7.25) and PALB2 (OR, 8.54) were associated with the highest breast cancer risks.[244] High ER-negative breast cancer risk was reported in individuals with pathogenic variants in RAD51D (OR, 7.82), while moderate ER-positive breast cancer risk was reported in individuals with pathogenic variants in CHEK2, ATM, ERCC3, and FANCC. Similarly, a case-control study of 3,286 women with African ancestry found significant associations between breast cancer risk and pathogenic variants in the following genes: BRCA1, BRCA2, PALB2, ATM, CHEK2, TP53, NF1, RAD51C, and RAD51D.[245]

There are caveats of multigene testing. Genes identified as part of multigene panel testing can be associated with varied breast cancer risk or confer no known risk.[230] There is also the possibility of finding a variant of uncertain significance (VUS). Even within a given gene, there may be differential risks on the basis of specific pathogenic variants.[246] A large population-based retrospective study using Surveillance, Epidemiology, and End Results (SEER) program data from Georgia and Los Angeles, California, found that multigene testing led to a twofold increase in the detection of pathogenic variants compared with BRCA-only testing in women with breast cancer.[247] VUS rates, however, were tenfold higher in the multigene panels, especially in African American women (44.5%) and Asian women (50.9%). Many centers now offer a multigene panel test instead of just BRCA1 and BRCA2 testing if there is a concerning family history of syndromes other than hereditary breast and ovarian cancer, or more importantly, to gain as much genetic information as possible with one test, particularly if there may be insurance limitations.

(Refer to the Multigene [panel] testing section in Cancer Genetics Risk Assessment and Counseling for more information about multigene testing, including genetic education and counseling considerations and research examining the use of multigene testing.)

References

American Cancer Society: Cancer Facts and Figures 2024. American Cancer Society, 2024. Available online. Last accessed June 21, 2024.

Ravdin PM, Cronin KA, Howlader N, et al.: The decrease in breast-cancer incidence in 2003 in the United States. N Engl J Med 356 (16): 1670-4, 2007. [PUBMED Abstract]

Quante AS, Herz J, Whittemore AS, et al.: Assessing absolute changes in breast cancer risk due to modifiable risk factors. Breast Cancer Res Treat 152 (1): 193-7, 2015. [PUBMED Abstract]

Feuer EJ, Wun LM, Boring CC, et al.: The lifetime risk of developing breast cancer. J Natl Cancer Inst 85 (11): 892-7, 1993. [PUBMED Abstract]

Yang Q, Khoury MJ, Rodriguez C, et al.: Family history score as a predictor of breast cancer mortality: prospective data from the Cancer Prevention Study II, United States, 1982-1991. Am J Epidemiol 147 (7): 652-9, 1998. [PUBMED Abstract]

Colditz GA, Willett WC, Hunter DJ, et al.: Family history, age, and risk of breast cancer. Prospective data from the Nurses' Health Study. JAMA 270 (3): 338-43, 1993. [PUBMED Abstract]

Slattery ML, Kerber RA: A comprehensive evaluation of family history and breast cancer risk. The Utah Population Database. JAMA 270 (13): 1563-8, 1993. [PUBMED Abstract]

Johnson N, Lancaster T, Fuller A, et al.: The prevalence of a family history of cancer in general practice. Fam Pract 12 (3): 287-9, 1995. [PUBMED Abstract]

Pharoah PD, Day NE, Duffy S, et al.: Family history and the risk of breast cancer: a systematic review and meta-analysis. Int J Cancer 71 (5): 800-9, 1997. [PUBMED Abstract]

Bevier M, Sundquist K, Hemminki K: Risk of breast cancer in families of multiple affected women and men. Breast Cancer Res Treat 132 (2): 723-8, 2012. [PUBMED Abstract]

Kharazmi E, Chen T, Narod S, et al.: Effect of multiplicity, laterality, and age at onset of breast cancer on familial risk of breast cancer: a nationwide prospective cohort study. Breast Cancer Res Treat 144 (1): 185-92, 2014. [PUBMED Abstract]

Reiner AS, Sisti J, John EM, et al.: Breast Cancer Family History and Contralateral Breast Cancer Risk in Young Women: An Update From the Women's Environmental Cancer and Radiation Epidemiology Study. J Clin Oncol 36 (15): 1513-1520, 2018. [PUBMED Abstract]

Albright FS, Kohlmann W, Neumayer L, et al.: Population-based relative risks for specific family history constellations of breast cancer. Cancer Causes Control 30 (6): 581-590, 2019. [PUBMED Abstract]

Mucci LA, Hjelmborg JB, Harris JR, et al.: Familial Risk and Heritability of Cancer Among Twins in Nordic Countries. JAMA 315 (1): 68-76, 2016. [PUBMED Abstract]

Chen J, Pee D, Ayyagari R, et al.: Projecting absolute invasive breast cancer risk in white women with a model that includes mammographic density. J Natl Cancer Inst 98 (17): 1215-26, 2006. [PUBMED Abstract]

Dupont WD, Page DL, Parl FF, et al.: Long-term risk of breast cancer in women with fibroadenoma. N Engl J Med 331 (1): 10-5, 1994. [PUBMED Abstract]

Zeinomar N, Phillips KA, Daly MB, et al.: Benign breast disease increases breast cancer risk independent of underlying familial risk profile: Findings from a Prospective Family Study Cohort. Int J Cancer 145 (2): 370-379, 2019. [PUBMED Abstract]

Boyd NF, Byng JW, Jong RA, et al.: Quantitative classification of mammographic densities and breast cancer risk: results from the Canadian National Breast Screening Study. J Natl Cancer Inst 87 (9): 670-5, 1995. [PUBMED Abstract]

Byrne C, Schairer C, Wolfe J, et al.: Mammographic features and breast cancer risk: effects with time, age, and menopause status. J Natl Cancer Inst 87 (21): 1622-9, 1995. [PUBMED Abstract]

Pankow JS, Vachon CM, Kuni CC, et al.: Genetic analysis of mammographic breast density in adult women: evidence of a gene effect. J Natl Cancer Inst 89 (8): 549-56, 1997. [PUBMED Abstract]

Boyd NF, Lockwood GA, Martin LJ, et al.: Mammographic densities and risk of breast cancer among subjects with a family history of this disease. J Natl Cancer Inst 91 (16): 1404-8, 1999. [PUBMED Abstract]

Vachon CM, King RA, Atwood LD, et al.: Preliminary sibpair linkage analysis of percent mammographic density. J Natl Cancer Inst 91 (20): 1778-9, 1999. [PUBMED Abstract]

Vachon CM, van Gils CH, Sellers TA, et al.: Mammographic density, breast cancer risk and risk prediction. Breast Cancer Res 9 (6): 217, 2007. [PUBMED Abstract]

Mitchell G, Antoniou AC, Warren R, et al.: Mammographic density and breast cancer risk in BRCA1 and BRCA2 mutation carriers. Cancer Res 66 (3): 1866-72, 2006. [PUBMED Abstract]

Ramón Y Cajal T, Chirivella I, Miranda J, et al.: Mammographic density and breast cancer in women from high risk families. Breast Cancer Res 17: 93, 2015. [PUBMED Abstract]

Thompson CM, Mallawaarachchi I, Dwivedi DK, et al.: The Association of Background Parenchymal Enhancement at Breast MRI with Breast Cancer: A Systematic Review and Meta-Analysis. Radiology 292 (3): 552-561, 2019. [PUBMED Abstract]

Terry MB, Liao Y, Kast K, et al.: The Influence of Number and Timing of Pregnancies on Breast Cancer Risk for Women With BRCA1 or BRCA2 Mutations. JNCI Cancer Spectr 2 (4): pky078, 2018. [PUBMED Abstract]

Johannsson O, Loman N, Borg A, et al.: Pregnancy-associated breast cancer in BRCA1 and BRCA2 germline mutation carriers. Lancet 352 (9137): 1359-60, 1998. [PUBMED Abstract]

Jernström H, Lerman C, Ghadirian P, et al.: Pregnancy and risk of early breast cancer in carriers of BRCA1 and BRCA2. Lancet 354 (9193): 1846-50, 1999. [PUBMED Abstract]

Friebel TM, Domchek SM, Rebbeck TR: Modifiers of cancer risk in BRCA1 and BRCA2 mutation carriers: systematic review and meta-analysis. J Natl Cancer Inst 106 (6): dju091, 2014. [PUBMED Abstract]

Valentini A, Lubinski J, Byrski T, et al.: The impact of pregnancy on breast cancer survival in women who carry a BRCA1 or BRCA2 mutation. Breast Cancer Res Treat 142 (1): 177-85, 2013. [PUBMED Abstract]

Jernström H, Lubinski J, Lynch HT, et al.: Breast-feeding and the risk of breast cancer in BRCA1 and BRCA2 mutation carriers. J Natl Cancer Inst 96 (14): 1094-8, 2004. [PUBMED Abstract]

Breast cancer and hormonal contraceptives: collaborative reanalysis of individual data on 53 297 women with breast cancer and 100 239 women without breast cancer from 54 epidemiological studies. Collaborative Group on Hormonal Factors in Breast Cancer. Lancet 347 (9017): 1713-27, 1996. [PUBMED Abstract]

Iodice S, Barile M, Rotmensz N, et al.: Oral contraceptive use and breast or ovarian cancer risk in BRCA1/2 carriers: a meta-analysis. Eur J Cancer 46 (12): 2275-84, 2010. [PUBMED Abstract]

Schrijver LH, Olsson H, Phillips KA, et al.: Oral Contraceptive Use and Breast Cancer Risk: Retrospective and Prospective Analyses From a BRCA1 and BRCA2 Mutation Carrier Cohort Study. JNCI Cancer Spectr 2 (2): pky023, 2018. [PUBMED Abstract]

Huber D, Seitz S, Kast K, et al.: Use of oral contraceptives in BRCA mutation carriers and risk for ovarian and breast cancer: a systematic review. Arch Gynecol Obstet 301 (4): 875-884, 2020. [PUBMED Abstract]

Kotsopoulos J, Lubinski J, Moller P, et al.: Timing of oral contraceptive use and the risk of breast cancer in BRCA1 mutation carriers. Breast Cancer Res Treat 143 (3): 579-86, 2014. [PUBMED Abstract]

Conz L, Mota BS, Bahamondes L, et al.: Levonorgestrel-releasing intrauterine system and breast cancer risk: A systematic review and meta-analysis. Acta Obstet Gynecol Scand 99 (8): 970-982, 2020. [PUBMED Abstract]

Breast cancer and hormone replacement therapy: collaborative reanalysis of data from 51 epidemiological studies of 52,705 women with breast cancer and 108,411 women without breast cancer. Collaborative Group on Hormonal Factors in Breast Cancer. Lancet 350 (9084): 1047-59, 1997. [PUBMED Abstract]

Gorsky RD, Koplan JP, Peterson HB, et al.: Relative risks and benefits of long-term estrogen replacement therapy: a decision analysis. Obstet Gynecol 83 (2): 161-6, 1994. [PUBMED Abstract]

Writing Group for the Women's Health Initiative Investigators: Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results From the Women's Health Initiative randomized controlled trial. JAMA 288 (3): 321-33, 2002. [PUBMED Abstract]

Chlebowski RT, Hendrix SL, Langer RD, et al.: Influence of estrogen plus progestin on breast cancer and mammography in healthy postmenopausal women: the Women's Health Initiative Randomized Trial. JAMA 289 (24): 3243-53, 2003. [PUBMED Abstract]

Beral V; Million Women Study Collaborators: Breast cancer and hormone-replacement therapy in the Million Women Study. Lancet 362 (9382): 419-27, 2003. [PUBMED Abstract]

Anderson GL, Limacher M, Assaf AR, et al.: Effects of conjugated equine estrogen in postmenopausal women with hysterectomy: the Women's Health Initiative randomized controlled trial. JAMA 291 (14): 1701-12, 2004. [PUBMED Abstract]

Schuurman AG, van den Brandt PA, Goldbohm RA: Exogenous hormone use and the risk of postmenopausal breast cancer: results from The Netherlands Cohort Study. Cancer Causes Control 6 (5): 416-24, 1995. [PUBMED Abstract]

Steinberg KK, Thacker SB, Smith SJ, et al.: A meta-analysis of the effect of estrogen replacement therapy on the risk of breast cancer. JAMA 265 (15): 1985-90, 1991. [PUBMED Abstract]

Sellers TA, Mink PJ, Cerhan JR, et al.: The role of hormone replacement therapy in the risk for breast cancer and total mortality in women with a family history of breast cancer. Ann Intern Med 127 (11): 973-80, 1997. [PUBMED Abstract]

Stanford JL, Weiss NS, Voigt LF, et al.: Combined estrogen and progestin hormone replacement therapy in relation to risk of breast cancer in middle-aged women. JAMA 274 (2): 137-42, 1995. [PUBMED Abstract]

Colditz GA, Egan KM, Stampfer MJ: Hormone replacement therapy and risk of breast cancer: results from epidemiologic studies. Am J Obstet Gynecol 168 (5): 1473-80, 1993. [PUBMED Abstract]

Rebbeck TR, Friebel T, Wagner T, et al.: Effect of short-term hormone replacement therapy on breast cancer risk reduction after bilateral prophylactic oophorectomy in BRCA1 and BRCA2 mutation carriers: the PROSE Study Group. J Clin Oncol 23 (31): 7804-10, 2005. [PUBMED Abstract]

Kotsopoulos J, Gronwald J, Karlan BY, et al.: Hormone Replacement Therapy After Oophorectomy and Breast Cancer Risk Among BRCA1 Mutation Carriers. JAMA Oncol 4 (8): 1059-1065, 2018. [PUBMED Abstract]

Gordhandas S, Norquist BM, Pennington KP, et al.: Hormone replacement therapy after risk reducing salpingo-oophorectomy in patients with BRCA1 or BRCA2 mutations; a systematic review of risks and benefits. Gynecol Oncol 153 (1): 192-200, 2019. [PUBMED Abstract]

Helzlsouer KJ, Harris EL, Parshad R, et al.: Familial clustering of breast cancer: possible interaction between DNA repair proficiency and radiation exposure in the development of breast cancer. Int J Cancer 64 (1): 14-7, 1995. [PUBMED Abstract]

Helzlsouer KJ, Harris EL, Parshad R, et al.: DNA repair proficiency: potential susceptibility factor for breast cancer. J Natl Cancer Inst 88 (11): 754-5, 1996. [PUBMED Abstract]

Abbott DW, Thompson ME, Robinson-Benion C, et al.: BRCA1 expression restores radiation resistance in BRCA1-defective cancer cells through enhancement of transcription-coupled DNA repair. J Biol Chem 274 (26): 18808-12, 1999. [PUBMED Abstract]

Abbott DW, Freeman ML, Holt JT: Double-strand break repair deficiency and radiation sensitivity in BRCA2 mutant cancer cells. J Natl Cancer Inst 90 (13): 978-85, 1998. [PUBMED Abstract]

Easton DF: Cancer risks in A-T heterozygotes. Int J Radiat Biol 66 (6 Suppl): S177-82, 1994. [PUBMED Abstract]

Kleihues P, Schäuble B, zur Hausen A, et al.: Tumors associated with p53 germline mutations: a synopsis of 91 families. Am J Pathol 150 (1): 1-13, 1997. [PUBMED Abstract]

Pierce LJ, Strawderman M, Narod SA, et al.: Effect of radiotherapy after breast-conserving treatment in women with breast cancer and germline BRCA1/2 mutations. J Clin Oncol 18 (19): 3360-9, 2000. [PUBMED Abstract]

Narod SA, Lubinski J, Ghadirian P, et al.: Screening mammography and risk of breast cancer in BRCA1 and BRCA2 mutation carriers: a case-control study. Lancet Oncol 7 (5): 402-6, 2006. [PUBMED Abstract]

Andrieu N, Easton DF, Chang-Claude J, et al.: Effect of chest X-rays on the risk of breast cancer among BRCA1/2 mutation carriers in the international BRCA1/2 carrier cohort study: a report from the EMBRACE, GENEPSO, GEO-HEBON, and IBCCS Collaborators' Group. J Clin Oncol 24 (21): 3361-6, 2006. [PUBMED Abstract]

Goldfrank D, Chuai S, Bernstein JL, et al.: Effect of mammography on breast cancer risk in women with mutations in BRCA1 or BRCA2. Cancer Epidemiol Biomarkers Prev 15 (11): 2311-3, 2006. [PUBMED Abstract]

Gronwald J, Pijpe A, Byrski T, et al.: Early radiation exposures and BRCA1-associated breast cancer in young women from Poland. Breast Cancer Res Treat 112 (3): 581-4, 2008. [PUBMED Abstract]

Pijpe A, Andrieu N, Easton DF, et al.: Exposure to diagnostic radiation and risk of breast cancer among carriers of BRCA1/2 mutations: retrospective cohort study (GENE-RAD-RISK). BMJ 345: e5660, 2012. [PUBMED Abstract]

Giannakeas V, Lubinski J, Gronwald J, et al.: Mammography screening and the risk of breast cancer in BRCA1 and BRCA2 mutation carriers: a prospective study. Breast Cancer Res Treat 147 (1): 113-8, 2014. [PUBMED Abstract]

Drooger J, Akdeniz D, Pignol JP, et al.: Adjuvant radiotherapy for primary breast cancer in BRCA1 and BRCA2 mutation carriers and risk of contralateral breast cancer with special attention to patients irradiated at younger age. Breast Cancer Res Treat 154 (1): 171-80, 2015. [PUBMED Abstract]

Reiner AS, Robson ME, Mellemkjær L, et al.: Radiation Treatment, ATM, BRCA1/2, and CHEK2*1100delC Pathogenic Variants and Risk of Contralateral Breast Cancer. J Natl Cancer Inst 112 (12): 1275-1279, 2020. [PUBMED Abstract]

Smith-Warner SA, Spiegelman D, Yaun SS, et al.: Alcohol and breast cancer in women: a pooled analysis of cohort studies. JAMA 279 (7): 535-40, 1998. [PUBMED Abstract]

Hamajima N, Hirose K, Tajima K, et al.: Alcohol, tobacco and breast cancer--collaborative reanalysis of individual data from 53 epidemiological studies, including 58,515 women with breast cancer and 95,067 women without the disease. Br J Cancer 87 (11): 1234-45, 2002. [PUBMED Abstract]

McGuire V, John EM, Felberg A, et al.: No increased risk of breast cancer associated with alcohol consumption among carriers of BRCA1 and BRCA2 mutations ages <50 years. Cancer Epidemiol Biomarkers Prev 15 (8): 1565-7, 2006. [PUBMED Abstract]

Dennis J, Ghadirian P, Little J, et al.: Alcohol consumption and the risk of breast cancer among BRCA1 and BRCA2 mutation carriers. Breast 19 (6): 479-83, 2010. [PUBMED Abstract]

Cybulski C, Lubinski J, Huzarski T, et al.: Prospective evaluation of alcohol consumption and the risk of breast cancer in BRCA1 and BRCA2 mutation carriers. Breast Cancer Res Treat 151 (2): 435-41, 2015. [PUBMED Abstract]

Brunet JS, Ghadirian P, Rebbeck TR, et al.: Effect of smoking on breast cancer in carriers of mutant BRCA1 or BRCA2 genes. J Natl Cancer Inst 90 (10): 761-6, 1998. [PUBMED Abstract]

Ghadirian P, Lubinski J, Lynch H, et al.: Smoking a