Hereditary cancer

Hereditary colorectal cancer

What is Hereditary colorectal cancer?

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.

Some basic facts about Hereditary colorectal cancer

Hereditary colorectal cancer is generally divided into two types:

Lynch syndrome
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
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.

Reference: National Cancer Institute, The genetics of colorectal cancer.

Role of genetics in diagnosis

Genetic testing may be appropriate if you have:

  • colorectal cancer diagnosed before age 50
  • more than one type of cancer, including colorectal cancer
  • a high number (10 to 1000 or more) of precancerous colorectal polyps
  • 3 or more individuals on the same side of your family with cancers that may suggest an inherited cancer syndrome, such as colon, rectal, stomach, thyroid, uterine, ovarian, or pancreatic cancer

Role of genetics in treatment

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:

  • provide an explanation for your personal or family history of cancer
  • evaluate your risk of developing future cancers
  • make informed medical decisions, including treatment, surveillance, and preventive options
  • qualify you for participation in clinical trials or research studies
  • identify other at-risk relatives for whom genetic testing is recommended

How do I arrange for genetic testing?

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.

Other names for Hereditary colorectal cancer

Hereditary nonpolyposis colorectal cancer (HNPCC)
Hereditary colon cancer