Is Colon Cancer Hereditary?

By Amy George, MS and Ashlyn Everett, MD

March is colon and rectal cancer awareness month. Many patients ask, “is colorectal cancer hereditary?” The short answer is, yes, it can be. But let’s dig a little deeper.

There are many risk factors for colon and rectal cancer, including obesity, smoking, alcohol, and inflammatory bowel disease (IBD). Your family history is also a part of your overall risk for developing colon cancer. If you have a family member (parent, sibling, or child) with colorectal cancer, you may be at higher risk of developing cancer.

• Average Risk: Patients without family history of colon cancer, screening is recommended starting at age 45.
• Increased Risk: Patients with family history of colorectal cancer; for example, if you have a first degree relative with colorectal cancer (parent, sibling, child), current nationalguidelines recommend beginning colonoscopy at age 40 or 10 years earlier than your relatives’ age of diagnosis, whichever comes first. The interval between colonoscopies may also be shorter, such as 5 years. Talk with your doctor about your family history and screening, as it may be recommended to start sooner than age 45.
• Hereditary Risk: Patients who are born with an altered gene that increases their chance of developing certain cancers such as colorectal cancer. We have guidelines for when and how to screen for colorectal cancer and other cancers. Hereditary cancer syndromes are less common but very important information for a family and future generations.

About 5% of patients with colon or rectal cancer were born with genetic mutations thatcontribute to the development of cancer. There are two major genetic conditions that are associated with colon cancer:

• Lynch syndrome, or hereditary non-polyposis colon cancer (HNPCC)
• Familial adenomatous polyposis (FAP)

There are other genes associated with colorectal cancer risk, but we will review these two genetic conditions in more detail.

Lynch Syndrome

Lynch syndrome is the most common inherited colon cancer condition, or syndrome. There are multiple genes that could be involved, including MLH1, MSH2, MSH6, and others. These genes provide the blueprint for proteins in the body called “mismatch repair proteins”. These important proteins help to repair small DNA damage that occurs every day in our bodies. When absent, there is a higher chance of DNA abnormalities, and over time this can increase the chances of developing certain types of cancers. The risk of colon cancer can be up to 60% in some cases of Lynch syndrome. Lynch syndrome is associated with endometrial cancer, ovarian cancer, stomach, pancreatic, ureter, and other cancers. In many cases, patients with Lynch syndrome will develop cancers at an earlier age. If you or a family member have Lynch syndrome, additional screening measures for these cancers are recommended. Be sure to speak with your doctor about the importance of screening for these cancers.

Familial Adenomatous Polyposis

About 1% of colon cancers are related to familial adenomatous polyposis (FAP). Individuals with FAP are born with one copy of their APC gene not functioning. This results in hundreds or thousands of polyps, or abnormal growths, in a person’s colon and rectum. Polyps will develop at very early ages (10-12 years) in FAP, with colon cancers starting as early as age 20. By the age of 40, most patients with FAP will develop colon cancer if they haven’t had surgery to remove their colon and prevent cancer. FAP is also associated with stomach, pancreatic, liver cancers, and others.

What Do I Do Next?

If you have a strong family history of colon cancer, you may want to consider asking if family members have had genetic testing. Genetic testing in a relative with colorectal cancer can be informative for the whole family if this is a feasible option. Cancer Genetic Counselors have expertise in hereditary cancer syndromes and cancer risk assessment to help you better understand your cancer risk, genetic testing options, and how to understand genetic testing results for you and your family. If you or your relative with colorectal cancer would like to schedule an appointment with a genetic counselor at a Clearview Cancer Institute location, call 256-705-4266. If you are over age 45 and have not had screening, talk to your doctor about one of the methods of colon cancer screening. Don’t wait! Colon cancer is very curable when detected early.

If you or a loved one has been diagnosed with colon or rectal cancer and would like to meet with one of our experts, please contact our Alliance Cancer Care team of experts for a consultation.