Gastrointestinal Cancers
Gastrointestinal cancers occur when DNA changes cause malignant (cancerous) cells to grow along the gastrointestinal tract. Learn about symptoms and treatment.
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Yale Medicine
The gastrointestinal (GI) tract is 25-foot-long pathway that extends from the mouth to the anus. Everything you eat passes through the esophagus and gets processed in the stomach and small intestines to extract nutrients. Ultimately, the waste is removed from your body through the colon and rectum.

Sometimes, a tumor can form in one of these organs, after a change in the DNA causes abnormal cells to grow. What’s behind this kind of change (known as a mutation)? It could be anything from underlying conditions to lifestyle choices to genetics.

Gastrointestinal cancer is common, both in the United States and worldwide. Treatments are more effective when the cancer is detected at an early stage—which, unfortunately, can be a challenge.

“Colorectal cancers are the most common and most treatable GI cancers in the United States,” says Yale Medicine’s Jeremy Kortmansky, MD, a medical oncologist. “About 5 to 10 percent occur from an inherited genetic risk factor, but the remaining cases happen sporadically. Most of these cases are related to unhealthy behaviors.”

The good news is that healthy lifestyle changes can help reduce the risk for GI cancer. “There is a clear reduction in risk with a lifestyle that includes regular exercise, a low-fat diet high in fruits and vegetables, minimal red meat, and moderate alcohol,” Dr. Kortmansky says.

Routine colorectal screening also markedly reduces the risk of colon cancer by finding and removing polyps before they have the chance to become cancerous, he says.

“We often consider the risk of colorectal cancer to increase with age,” says Dr. Kortmansky, “but recently, the incidence in patients under 50 is rapidly increasing. For this reason, the American Cancer Society recently recommended that routine colorectal cancer screening should start at age 45. It is important to catch colorectal cancers early, because if we do, they are highly curable.”