Genetic Testing for Colorectal Cancer

Hello, my name is Anna McGill and I am the genetic counselor here at Alta Bates Summit Medical Center. As a genetic counselor, it is my job to help women and men with a personal or family history of cancer. In certain cases, cancer can be attributed to a change, or mutation, in a gene. These suspicious cancers often occur at young ages, with multiple family members affected, over multiple generations and may come clustered with specific types of cancer being more common in occurrence.

There are two types of hereditary colon cancer. The first types of colon cancer syndromes are called polyposis syndromes. These syndromes cause a person to develop hundreds to thousands of polyps in their colon. When a person is affected with a polyposis syndrome; their chance to develop colon cancer approaches 100% in their lifetime. Many people with a polyposis syndrome do not have a family history.

The second type of hereditary colon cancer is called nonpolyposis colon cancer. In hereditary nonpolyposis colon cancer, there are fewer polyps found in the colon than in those with polyposis syndromes; however, these polyps develop into cancer faster than normal polyps and cancer may result at earlier ages. Colon cancer risk in those affected with hereditary nonpolyposis cancer ranges from 60%-80%. There are also other cancers associated with this syndrome including endometrial and ovarian cancer.

If an individual is found to carry a change in a colon cancer predisposition gene, there are several options to decrease the chance that that individual will develop cancer. Both increased screening and preventative surgical measures have proved to be effective methods to decrease the incidence of cancer.