A comparison of cancer risk in Crohn's disease and ulcerative colitis.

The authors estimated cancer risk among 589 patients hospitalized with Crohn's disease between 1960-1976 by calculating the ratios of observed number of cancers (O) in our hospital sample to the expected number of cancers (E) based on the age- and sex-specific cancer rates of a standard population. The authors then compared these O/E ratios with the O/E ratios similarly calculated among 267 patients hospitalized with ulcerative colitis. The risk of colorectal cancer was significantly increased in Crohn's disease (O/E = 6.9, P less than 0.001). This increase was similar in magnitude to that found in left-sided ulcerative colitis (O/E = 8.6, P less than 0.001) but was much less than that found in universal ulcerative colitis (O/E = 26.5, P less than 0.001). The incidence of small bowel cancer was greatly increased in the combined group of regional enteritis and ileocolitis (O/E = 85.8, P less than 0.001), and even more so in the regional enteritis group alone (O/E = 114.5, P less than 0.001). The incidence of extraintestinal cancer did not increase in any of the patient groups.