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

The authors estimated cancer risk among 579 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< 0.001). This increase was similar in magnitude to that found in left‐sided ulcerative colitis (O/E = 8.6, P< 0.001) but was much less than that found in universal ulcerative colitis (O/E = 26.5, P< 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< 0.001), and even more so in the regional enteritis group alone (O/E = 114.5, P< 0.001). The incidence of extraintestinal cancer did not increase in any of the patient groups.