Colorectal cancer is the third most commonly diagnosed cancer in both men and women. Approximately 5 to 10 percent of patients with colorectal cancer have a pathogenic genetic variant that increases their risk of developing the disease.
Hereditary colorectal cancer is generally divided into two types:
Lynch syndrome (also known as hereditary nonpolyposis colorectal cancer syndrome) is the most common cause of hereditary colorectal cancer. Approximately 1 in 400 people have a genetic variant which can cause Lynch syndrome. These variants can increase a person’s lifetime risk of developing colorectal cancer up to 80 percent and can also increase the risk of developing other cancers including uterine, ovarian, stomach, pancreatic, and kidney cancer.
Polyposis syndromes are characterized by the development of numerous precancerous polyps (small clumps of cells that forms on the lining of the colon). Familial adenomatous polyposis (FAP) is the most common polyposis syndrome and is caused by a variant in the APC gene. Classic FAP can increase a person’s lifetime risk of developing colorectal cancer to over 95 percent. Genetic variants in genes related to polyposis syndromes can also increase the risk of other cancers including stomach, small bowel, pancreatic, and thyroid cancer.
Genetic testing may be appropriate if you have:
If you have an elevated risk of developing cancer based on your genetic test result, you can work with your healthcare provider to create a plan designed to prevent a cancer entirely, or help to identify a cancer at an earlier, more treatable stage.
In addition, genetic testing may help:
Your physician will assist you in identifying and arranging for the appropriate genetic test(s). If you have specific questions or concerns about the testing, your physician may refer you to a genetic counselor to discuss further. Once you are ready to proceed with genetic testing, you will need to submit either a blood or saliva sample.
Hereditary nonpolyposis colorectal cancer (HNPCC)
Hereditary colon cancer