Hereditary proximal colonic cancer.

Ten families prone to cancer of the colon (in the absence of familial polyposis coli) have been investigated. A significantly greater frequency of carcinomas of the proximal colon was evident relative to non-familial colonic cancers (65% versus less than 35%, P less than .001). Moreover, family members with proximal colonic cancers experienced significantly enhanced survival, compared with family members with distal colonic or rectal cancers. Findings consistent with a genetic predisposition included early mean age at onset (45 years) and a high frequency (40%) of multiple primary cancers in the patients studied. The results are in accord with reported findings in 11 similar kindreds from the literature, and strongly suggest the existence of a heritable variety of colonic cancer in which the proximal colon is at particularly high risk. Extraordinary early diagnostic measures, including colonoscopy, are indicated for members of such families.