Is Colorectal Cancer Hereditary? 

by Jake Newby

| 3 min read

Is Colorectal Cancer Hereditary?
Colorectal cancer is currently the third most common cancer in the world. It contributes to 10.7% of new cancer cases. The American Cancer Society (ACS) projects there to be 106,190 new cases of colon cancer and 44,850 new cases of rectal cancer in the United States in 2022. One of the many risk factors for colorectal cancer is family history. Though most colorectal cancer cases are discovered in people without a family history of the disease, as many as 33% of all people who develop colorectal cancer have other family members who have had it. When cancer does run in the family, it is because of inherited genes, shared environmental factors or a combination of both factors.

Common inherited colorectal cancer syndromes

Approximately five to 10% of colon cancer itself is hereditary, based on DNA mutations that can be passed on in families. These are known as inherited mutations. Despite that relatively low figure, if you have family members who have either suffered from Lynch syndrome or developed adenomatous polyps, you have a higher risk for developing colon cancer.

Lynch syndrome (Hereditary non-polyposis colon cancer)

The most common hereditary colorectal cancer syndrome is Lynch syndrome, which is associated with a genetic predisposition to different cancer types. This means people diagnosed with it have an increased risk of developing certain types of cancer before they turn 50.  Above all, people with Lynch syndrome have a significantly increased risk of developing colorectal cancer. Lynch syndrome accounts for roughly 4% of all colorectal cancers and is one of the most common hereditary cancer syndromes overall. Lynch syndrome is caused by a genetic change called a mutation that occurs in one of five genes. This mutation impacts the body’s ability to repair damage to cells as they grow, which over time can lead to cancer.

Familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is a rare condition caused by inherited changes to a person’s APC gene, which is a tumor suppressor gene in charge of keeping cell growth in check.  People with inherited changes to APC genes experience uncontrolled cell growth that leads to the development of many polyps in the colon. The treatment for FAP is to remove the colon to prevent the development of colon cancer which can occur before the age of 40.

The importance of family health history

Those aware of their family history of colorectal cancer should share that information with their doctor and can take the necessary steps to lower their risk.  If you have a relative who has been diagnosed with colorectal cancer at a young age, your doctor may recommend screening tests such as a colonoscopy earlier than the routine screening age of 45. Here are tips from the Centers for Disease Control and Prevention (CDC) to collect your family’s health history:
  • Document which relatives have had cancer, the type(s) of cancer they have had, and the ages at which they were diagnosed.
  • Include your parents, sisters, brothers, children, grandparents, aunts, uncles, nieces, and nephews.
  • List the age and cause of death for relatives who have died.
  • Make sure to document both your mother’s side of the family and your father’s side of the family.
  • Report any history of polyps that each relative has had.
  • Share your family health history with your doctor.
  • Update your family health history regularly and alert your doctor to any new diagnosis.
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