Hereditary colon cancer syndromes

Colon cancer can be hereditary. One of the biggest risk factors for colon cancer is having a family history of the disease.

There are known gene mutations that lead to hereditary colon cancer syndromes. The two most common hereditary colon cancer syndromes are hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch syndrome, and familial adenomatous polyposis (FAP).

The children of those who carry these genes have a 50 percent chance of inheriting them. Those with these genes will most likely develop colorectal cancer but preventative options can help. Hereditary colon cancer syndromes cause less than 5 percent of all colon cancer cases.

Hereditary nonpolyposis colorectal cancer (HNPCC)

HNPCC is the most common hereditary colon cancer syndrome. Most people who inherit HNPCC will develop colon cancer. The cancer often develops before age 50. Having it increases your risk of developing other HNPCC-related cancers such as kidney, ovarian, and stomach cancer.

HNPCC criteria

Doctors use a set of criteria to determine if HNPCC is present in your family. These criteria are known as the Amsterdam criteria.

The criteria used to determine if HNPCC is present in your family

• Three family members with HNPCC-related cancer
• Two successive generations with HNPCC-related cancer
• Two affected family members are first degree relatives of another family affected member
• One family member develops HNPCC cancer before age 50
• FAP is not present in any family member’s diagnosis

HNPCC screening

Doctors can determine if you have the HNPCC gene mutation with genetic testing. The test is done by giving a blood sample.

For those with HNPCC families, routine cancer screenings should start between the ages of 20 and 25. Colonoscopies are recommended for family members who are 10 years younger than the youngest family member diagnosed with cancer. This allows doctors to detect and treat any abnormalities as early as possible.

HNPCC treatment

A colectomy is the best way to prevent or treat cancer from HNPCC. This operation removes the colon. Continual, regular screenings are necessary to check for cancer elsewhere.

Familial adenomatous polyposis (FAP)

FAP is an inherited polyposis syndrome. This syndrome causes thousands of polyps to develop in the large intestine. Polyps are small, benign lesions. Overtime they can grow and develop into cancer. Due to the number of polyps in those with FAP, they have a 100 percent chance of developing colon cancer. FAP is present in about 1 percent of those diagnosed with colorectal cancer each year. Those with FAP also have an increased risk of developing cancer in areas such as the liver, small intestine, and stomach.

FAP diagnosis

Many different types of inherited polyposis syndromes as well as sub-types of FAP exist. An exact diagnosis depends on number of polyps present, the age at which they first developed, and additional criteria. A person with more than 100 colorectal polyps is considered to have FAP. Polyps can be found through colonoscopy procedures.

Colorectal polyp symptoms

Typically, colorectal polyps have no symptoms and it’s unusual to notice them yourself.

Possible symptoms that should be checked by your doctor

• A change in normal bowel habits that last for more than a couple weeks
• Abdominal pain
• Blood or mucus in the stool

FAP screening

Genetic testing is available to determine if you have the FAP gene mutation. Doctors can take a sample of your blood and compare it to a family member’s that is affected with FAP.   

Colonoscopies are recommended every one to two years beginning at age 10 for those with FAP families. Tests may also be done to screen the upper part of the gastrointestinal tract, such as the stomach, for polyps. As the condition is monitored, the doctor and patient will typically decide when surgery should be performed to prevent cancer.

FAP treatment

Surgery is the best way to treat FAP and prevent cancer. This normally involves removing the colon and rectum.