What is Inherited Colorectal Cancer?
Each year, approximately 140,000 individuals are diagnosed with colorectal cancer and more than 50,000 die from the disease. Colorectal cancer is the second leading cause of cancer-related deaths in the United States, and up to 5-6% of individuals in this group have cells in their bodies that are pre-programmed from birth to develop colorectal cancer. This vulnerability comes from a mutation in a gene that causes the gene to not function properly and cancer to develop as a result. These mutations are inherited in a parent-to-child manner and are the basis of inherited colorectal cancer syndromes.
Two of the more common inherited syndromes are familial adenomatous polyposis (FAP) and hereditary non-polyposis colon cancer (HNPCC). FAP is characterized by the development of colon “polyps” (abnormal growths of cells that form lumps, tumors or masses) that almost always progress to cancer if not removed in a timely manner. Polyp development can start as early as puberty, and there is a 100% lifetime risk of developing colorectal cancer at an average age of 40 years unless your colon is removed as a preventative measure. Even after your colon is removed, polyps and cancer can still develop in the small intestine pouch or residual rectum that is left in your body after surgery. For this reason, it is important that you and your family members have regular and close follow-up surveillance with an endoscopic exam (a flexible medical instrument with a camera is used for this purpose).
Since the abnormal gene that causes FAP is present in all of the body’s cells, other organs in your body can also develop growths or masses. Polyps form in the stomach and small intestine in more than 80% of patients, and duodenal cancer develops in up to 12% of patients. As a result, routine screening of the stomach and small intestine with an upper endoscopy scope is important. Thyroid cancer and desmoids (a type of tumor that develops from the soft connective tissues in the body) may also occur in FAP. Close follow-up of you and your at-risk family members is the key to reducing cancer risk.
HNPCC, or hereditary non-polyposis colon cancer, is a clinical syndrome that is associated with the development of a variety of cancers. HNPCC accounts for 3% of all newly diagnosed cases of colorectal cancer. About 80% of patients with HNPCC develop cancer in their lifetime, most commonly in the colon and rectum, but cancer may also develop in the uterus (endometrium), ovaries, small intestine, urinary tract, liver, kidneys and bile duct.
A diagnosis of HNPCC is made with a family medical history or pedigree. Genetic testing may also be ordered. Because colorectal cancer in HNPCC families often develops before the recommended age to begin colorectal screening in the general population, it is very important to start preventative screening at an early age. Screening exams may include colonoscopies and pelvic examinations with a transvaginal ultrasound.
Coming soon: Information on juvenile polyposis syndrome (JPS), MYH-associated polyposis (MAP), and Peutz-Jeghers syndrome (PJS).