Common Inheritance of Susceptibility to Colonic Adenomatous Polyps and Associated Colorectal Cancers

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Abstract
We studied 670 persons in 34 kindreds by flexible proctosigmoidoscopic examination (60 cm) to determine how frequently colorectal adenomas and cancers result from an inherited susceptibility. Kindreds were selected through either a single person with an adenomatous polyp or a cluster of relatives with coIonic cancer. The kindreds all had common colorectal cancers, not the rare inherited conditions familial polyposis coli and nonpolyposis inherited colorectal cancer. Likelihood analysis strongly supported the dominant inheritance of a susceptibility to colorectal adenomas and cancers, with a gene frequency of 19 percent. According to the most likely genetic model, adenomatous polyps and colorectal cancers occur only in genetically susceptible persons; however, the 95 percent confidence interval for this proportion was 53 to 100 percent.