On Apr. 19, 2021, the Mayo Clinic announced a study that bolstered evidence that colorectal cancer is often imprinted in family genes and passed on from one generation to the next.

In the study, published in Clinical Gastroenterology and Hepatology, researchers found 1 in 6 patients with colorectal cancer had an inherited cancer-related gene mutation, which likely predisposed them to the disease. In addition, the researchers discovered that 60% of these cases would not have been detected if relying on a standard guideline-based approach.

“We found that 13.5% of patients had an inherited mutation in a gene associated with the development of their cancer,” says Niloy Jewel Samadder, M.D., a Mayo Clinic gastroenterologist and hepatologist, who is the study’s author. “Everyone has some risk of developing cancer, and in most cases the disease develops by chance. However, some people are genetically predisposed to developing certain types of cancer, such as breast or colon cancers.”

A genetic mutation can cause a gene to malfunction and lead to a cell becoming cancerous. Although many mutations that cause cancer happen by chance in a single cell, the study confirms that nearly 10%–25% are inherited mutations that set off a cycle of events that can lead to cancer. Dr. Samadder says uncovering these hidden inherited genetic mutations could lead to opportunities for cancer management in families and targeted cancer therapies that can save lives.

In the two-year Interrogating Cancer Etiology Using Proactive Genetic Testing (INTERCEPT) study, Mayo Clinic provided free genetic testing and counseling to 3,084 Mayo Clinic patients as part of their standard cancer care. The project, representing the largest known multicenter study of universal testing of patients with cancer, included a broad mix of cancer stages and types, including breast, colorectal, lung, ovarian, pancreatic, bladder, prostate and endometrial cancers.

The researchers were surprised to find that the standard guidelines physicians relied on to determine which patients with cancer should undergo genetic testing were only able to identify 48% of the patients with an inherited genetic mutation. “More than half of the patients who developed cancer due to inherited mutations were being missed, and that has major implications for family members,” Dr. Samadder says.

Dr. Samadder says equally important to the discovery of a patient’s inherited cancer mutation is the potential for patients to share the heretible-cause of their disease with their relatives, allowing family members to pursue care for earlier disease detection and cancer management.