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- hereditary non-polyposis colorectal cancer
- familial adenomatous polyposis
- cancer screening
- genetic testing
Hereditary colorectal cancer syndromes account for about 6% of cases of colorectal cancer. People with gene mutations associated with hereditary non-polyposis colorectal cancer (HNPCC) and familial adenomatous polyposis (FAP) have a lifetime risk of colorectal cancer of 80%–100% and should undergo more frequent colorectal screening, as well as additional surveillance for associated extracolonic tumours. Despite the proven benefit of cancer screening and the recent publication of guidelines for genetic testing in hereditary colorectal cancer,1 there is little information about the prevalence of appropriate cancer surveillance among people at risk for HNPCC or FAP.
The HNPCC syndrome is inherited as an autosomal dominant trait in which affected people have a greater than 80% risk of developing colorectal cancer, which is often right sided and appears at an early age (4th and 5th decades).2 Although mutations in DNA mismatch repair genes (hMLH1 and hMSH2) have been identified in 30%–64% of these families,3 genetic testing is not informative in many cases and most people are diagnosed with HNPCC on the basis of clinical criteria and family cancer history. Colonoscopy with polypectomy at intervals of one to three years has been shown to be effective in reducing the incidence of colorectal cancer among people at risk of HNPCC.4 Because of accelerated tumour growth associated with HNPCC, newer recommendations advocate colonoscopy every one to two years, beginning at age 20–25.3,5 As HNPCC confers a risk of endometrial cancer of 40%–60%,6 expert panels currently recommend annual transvaginal ultrasound or endometrial aspirate for women at risk for HNPCC beginning at age 25–35.3,7
The FAP syndrome is also inherited as an autosomal dominant trait, and is characterised by the development of hundreds to thousands of adenomatous polyps in the colon. The risk of colorectal cancer is 100% if the …
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