[An epidemiological study on familial predisposition to large bowel cancer].

To investigate hereditary factors in large bowel cancer, we studied the clinical characteristics of familial predisposed patients. The hospital records of 937 male and female patients, excluding those with familial polyposis coli, seen at the Cancer Institute Hospital, Tokyo between 1964-1979 were reviewed. The cases were grouped by sites and multiplicity of the tumors. A total of 96 patients (6%) had one or more relatives with colo-rectal cancer. The frequency of familial occurrence was highest (20%) for multiple cancers and lowest (4%) for rectal cancer. The average age at surgery was 55.3 years in familial patients and 56.9 years in non-familial patients. The lower age at surgery in familial compared to non-familial patients was significant for multiple cancers and remarkable, though not significant, for proximal colon cancer and double primary cancers. We posit that the hereditary type of large bowel cancer may be characterized by familial, early age at onset, proximity and multiplicity of the intestinal tumor, and double primary cancers in other organs. While polyp formation seems to be largely affected by environmental factors, its occurrence may be enhanced by hereditary factor.