Background and Aims: Familial predisposition as a risk for colorectal cancer in ulcerative colitis has not been rigorously explored. The aim of this study was to compare colorectal cancer frequency among kindreds of patients who had ulcerative colitis and colorectal cancer with that of control patients who had ulcerative colitis but no cancer. Methods: Questionnaires were mailed to subjects to assess cancer occurrence among relatives. Eligible cases included 174 ulcerative colitis patients with colorectal cancer seen at Mayo Clinic in 1976-1994; 174 contemporaneous ulcerative colitis controls without cancer were matched on birth year, sex, and extent and duration of colitis. Results: The responding 147 case and 150 control subjects reported on 1044 and 1090 first-degree relatives, respectively. Colorectal cancer occurred in 14.3% case kindreds and 6.7% control kindreds (P = 0.03). By logistic regression, a family history of sporadic colorectal cancer was an independent risk factor for cancer in ulcerative colitis (odds ratio, 2.33; 95% confidence interval, 1.06-5.14; P = 0.03). Conclusions: A familial association exists between colorectal cancers occurring with ulcerative colitis and those in the general population. Colorectal cancer in persons with ulcerative colitis represents a risk factor for colorectal cancer in their noncolitic relatives. Likewise, a family history of sporadic colorectal cancer increases the risk of colorectal cancer with ulcerative colitis.
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