Vanderbilt-Ingram Cancer Center

Family Cancer Risk Service

Hereditary Colon Cancer

Background

Cancer of the colon or rectum, colorectal cancer, is the third most common type of cancer in the United States, with nearly 150,000 diagnoses every year. About 1 in 18 individuals in this country will develop colorectal cancer sometime during his or her lifetime.

Colon Cancer in Families

Most cases of colorectal cancer are not hereditary. However, an estimated 5% of colon cancer cases are due to inherited alterations in single cancer susceptibility genes. An alteration of this type can be passed from generation to generation and increase the risk of developing colon and other cancers.

The most common hereditary colorectal cancer syndromes are called Hereditary Non-polyposis Colorectal Cancer (HNPCC) and Familial Adenomatous Polyposis (FAP). There are other rare genetic conditions, as well, which can increase the risk of colorectal cancer.

Hereditary Non-Polyposis Colorectal Cancer (HNPCC) or Lynch syndrome

Hereditary Non-Polyposis Colorectal Cancer, also known as Lynch syndrome, is a hereditary condition characterized by an increased risk of colorectal, uterine, and other cancers, which can develop at earlier ages than one would expect in the general population. In addition to colon and uterine cancer, individuals with HNPCC are at an increased risk for cancer of the ovary, stomach, urinary tract, small bowel, and bile duct. HNPCC accounts for approximately 2%-4% of all colon cancers.

Familial Adenomatous Polyposis (FAP)

Familial adenomatous polyposis is an inherited condition characterized by the development of hundreds to thousands of polyps in the colon and rectum at a young age, usually in the teens to 20s. A subtype of FAP (called Attenuated FAP) is characterized by fewer polyps and later age of onset. The major risk of FAP is development of colorectal cancer if not recognized and managed appropriately. Other features sometimes seen in FAP include polyps in the small intestine and stomach, soft-tissue tumors of the skin, jawbone growths, and brain tumors. FAP accounts for approximately 1% of all colon cancers.

Am I at Increased Risk for Carrying a Colon Cancer Susceptibility Gene?

• Have you or any family members been diagnosed with colon or rectal cancer or polyps at an early age (before age 50)?
• Do you have a close relative who has been diagnosed with colon cancer more than once (separate cancers, diagnosed at the same or different time) or colon cancer and another cancer such as uterine or ovarian.
• Does anyone in the family have a history of multiple colon polyps?
• Do you have a blood relative who has been found to carry an alteration in a colon cancer susceptibility gene?

If you answered "YES" to any of these questions, you may be at increased risk for carrying an alteration in a colon cancer susceptibility gene. Familial cancer risk counseling can help you to understand your cancer risks and the management options available to you.

Is Genetic Testing Right for Me?

Genetic testing for alterations in some of the colon cancer susceptibility genes is now available. The decision to undergo genetic testing is a very personal one and there are many issues to consider before making this decision. Cancer risk assessment and counseling is an important step before making the decision to pursue genetic testing. If you are concerned about your risk of cancer, cancer risk counseling can help you better understand your risks and the options available to you and your family.

See also:

• The Vanderbilt Hereditary Colorectal Cancer Registry

Vanderbilt-Ingram Cancer Center
Family Cancer Risk Service
Vanderbilt Health-One Hundred Oaks
719 Thompson Lane Suite 25107
Nashville, TN 37204

(615) 343-0738
or toll-free (877) 688-7555