| HEREDITARY COLORECTAL CANCER (CRC) - Colon cancer is the 3rd most common type of cancer. Approximately 150,000 cases are diagnosed in the US each year.
- 15% to 50% of CRC may have a genetic component. Having a 1st-degree relative (a parent or a sibling) with CRC increases the risk of developing CRC.
- Family history is most helpful in deciding if a cancer is hereditary. Look for:
- early diagnosis (before age 50)
- multiple family members with CRC
- multiple family members with colon polyps, especially in an early age
- family history of gynecologic, stomach, ureter, or small intestine cancers
- Ashkenazi Jewish background in a family with at least one person with colon cance
- There are two well-known forms of hereditary CRC:
- hereditary nonpolyposis colorectal cancer (HNPCC) accounts for about 6% of all hereditary CRC
- familial adenomatous polyposis (FAP) accounts for about 1% of all hereditary CRC.
FAP And HNPCC Have Different Features FAP | HNPCC | More than 100 colon polyps (often thousands) | Few, if any, colon polyps | Mean age of polyposis onset = 16 yrs; Average age of CRC diagnosis = 39 yrs | Mean age of CRC diagnosis = 41-44 yrs (range 19-83 yrs) | Predominantly left-sided CRC | Predominantly right-sided colorectal tumors; More than one CRC in 30-34% of individuals | Patients have increased risk of thyroid, duodenal, stomach cancer, brain tumors, other manifestations | Patients and other family members have increased risk of endometrial, gastric, small-intestine, liver, and ovarian cancer | Caused by mutations in APC gene | Caused by mutations in one of 5 different genes |
- A person who carries a mutation in one of the hereditary CRC genes has a significantly increased risk over the general population to develop CRC:
- In individuals with FAP, this risk is almost 100%.
- In individuals with HNPCC, the risk is about 80% by age 80.
- People carrying mutations for these conditions are recommended to have earlier and more frequent colon surveillance.
- Dietary factors and lifestyle changes can also influence the occurrence of CRC.
- Genetic testing is available for some forms of hereditary CRC, but is not appropriate for everyone.
Material published on this web site is for informational purposes only. Readers are encouraged to confirm the information contained herein with other sources. Patients and consumers should review the information carefully with their professional healthcare provider. The information is not intended to replace medical advice offered by physicians. |
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