INCIDENCE OF HEREDITARY NONPOLYPOSIS COLORECTAL-CANCER IN A POPULATION-BASED STUDY OF 1137 CONSECUTIVE CASES OF COLORECTAL-CANCER

Background Previous reports have indicated that 5-13 per cent of color ectal cancer is hereditary. However, the proportion of cases arising a s a result of mutations in the hereditary non-polyposis colorectal can cer (HNPCC) genes remains to be determined. Methods This study is a pa rt prospective, part retrospective review of all cases df colorectal c ancer from a district hospital over 14 years. Some 1137 consecutive pa tients with colorectal cancer were questioned about their family histo ry of cancer and details were logged on a database. For the past 4 yea rs each case has been re-evaluated where possible. Results Some 118 pa tients indicated initially that they had a first-degree relative with colorectal cancer, but on re-evaluation there were significant discrep ancies. Only three cases (0.3 per cent) occurred in families which str ictly fulfilled the criteria for HNPCC and there were no cases of fami lial adenomatous polyposis. A total of 16 patients (1.4 per cent) fulf illed looser criteria for HNPCC. Conclusion This population-based stud y has shown a lower frequency of familial bowel cancer than previous s tudies and may reflect a lower incidence of inherited mutations in the HNPCC DNA mismatch repair genes than is currently accepted.