Some families have a higher risk of cancer due to inherited gene mutations. These are often referred to as hereditary cancer syndromes. Here are a few common inherited cancer syndromes related to colorectal cancer:
Lynch syndrome is associated with a genetic predisposition for colon and many other types of cancer. An estimated 1 in 279 Americans have Lynch syndrome, but most are unaware.
Also known as hereditary non-polyposis colorectal cancer (HNPCC), Lynch syndrome is the most common hereditary cause of colorectal cancer and accounts for about 2-4% of all colorectal cases according to the American Cancer Society. In most cases, the inherited defect is in either the MLH1, MSH2, MSH6, PMS2 or EPCAM gene. However, there are other genes that can also cause Lynch syndrome. People with Lynch syndrome have a significantly higher lifetime risk of developing colorectal cancer, with many as high as 50%, depending on which gene is affected. They are also at increased the risk of other cancers, including endometrial, ovarian, stomach, and small intestine cancers.
Lynch syndrome is an autosomal dominant condition, meaning a person only needs to inherit the gene from one parent to be affected. Talk to a genetic counselor about being screened for Lynch syndrome if you have a strong family history of Lynch-related cancers in first degree (parent, siblings, and children) and second degree (aunts, uncles, grandparents, etc.) relatives on the same side of the family tree.
Lynch-related cancers include colorectal cancer, endometrial cancer, ovarian cancer, stomach cancer, small bowel cancer, ureter or renal pelvis cancer, bladder cancer, bile duct cancer, pancreatic cancer, or sebaceous adenomas of the skin.
Monitoring and Treatment
FAP is an inherited cancer condition caused by mutations (changes) in the APC gene, and resulting in the growth of hundreds to thousands of polyps in the colon and rectum, often starting between the ages of 10 and 12. If untreated, this condition is associated with a nearly 100% lifetime risk of colorectal cancer by age 40. Many patients with FAP choose to remove their colon to prevent colorectal cancer from developing.
FAP is a rare disease. Estimated to affect about 1 in 8,000 people and about 0.5% of all colorectal cancer cases. A FAP diagnosis will be made if a patient has at least 100 polyps and an APC mutation found during genetic testing.
Like Lynch syndrome, FAP is an autosomal dominant condition. Patients with a first-degree relative with FAP or a personal history of numerous polyps (more than 10 cumulative colorectal adenomas) should be screened for FAP. Individuals with FAP also have an increased risk of other cancers, including stomach, small intestine, pancreas, and liver.
The average age for colon polyps associated with FAP begins is 16. Families with a known FAP condition should start colorectal cancer screening with colonoscopy as early as age 10.
Monitoring and Treatment
MAP is an autosomal recessive condition caused by inheriting mutations of the MUTYH gene from both parents. The MUTYH is crucial for repairing DNA during normal cell renewal. If the condition is inherited from only one parent, that person is considered a carrier.
Individuals with MAP may develop fewer polyps than those with FAP, but they still have an increased risk of colorectal cancer. This condition causes less than 1% of all colon cancers, but by age 60 more than half of people with MAP will develop colon cancer. Without colonoscopy screening to remove polyps and monitor colon health, more than 80% of people with MAP could develop colorectal cancer during their lifetime.
Talk to a genetic counselor about testing for MAP if you have a personal history of 10 or more colorectal adenomas by age 60, 20 or more colorectal adenomas at any age, 5+ sessile serrated polyps in the first half of the colon, OR a family history of MAP or a large number of polyps.
MAP is an extremely rare condition, affecting approximately 1 in 20,000 to 40,000 people. People with a known MAP diagnosis should begin colorectal cancer screening with a colonoscopy between the ages 25 and 30. Individuals with MAP also have an increased risk of other GI (gastrointestinal) tract, breast, ovary, bladder, and thyroid cancer.
Monitoring and Treatment
FCCTX may be considered a subtype of Lynch syndrome, but while Lynch syndrome tumors show microsatellite instability (MSI), FCCTX tumors are microsatellite stable (MSS). (see biomarkers page for more)
The cause for FCCTX is still unknown, and research is ongoing.
If you have a strong family history with no other known genetic syndrome, talk to a genetic counselor about your risks, whether genetic testing is appropriate, and if earlier colonoscopy screening is needed.
Families with a strong history of colorectal cancer are recommended to begin colonoscopy screening 5 to 10 years before the earliest onset case, with additional colonoscopies every 3 to 5 years after.
Information on these pages is provided for educational purposes only. Consult your physician before making any medical decisions.
