Incidence of colorectal cancer and all cause mortality in non-selected patients with ulcerative colitis and indeterminate colitis in Malmö, Sweden

Cancer morbidity and all cause mortality were studied prospectively in all patients with definite and probable ulcerative colitis and indeterminate colitis diagnosed from 1958 to 1982, in the city of Malmö, Sweden. The follow-up to Jan. 1, 1990 was complete for all but ten patients. Nine of the 471 patients with ulcerative colitis and three of the 100 patients with indeterminate colitis developed colo-rectal cancer. The incidence of colorectal cancer in ulcerative colitis was 1.4 per 1000 person-years. The observed number of cases was 2.1 times higher than expected; (95% C.I. 1.0-4.1), based on the age- and sex-specific cancer incidence in the city during the study period. Indeterminate colitis was associated with a higher colorectal cancer risk than ulcerative colitis; 2.4 per 1000 person-years; (SMR 8.6, 95% C.I. 1.8-25.1). Both conditions were associated with a slight increased mortality rate, for ulcerative colitis 12.6 per 1000 person-years; (SMR 1.3, 95% C.I. 1.0-1.5), and for indeterminate colitis 11.7 per 1000 person-years; (SMR 2.7, 95% C.I. 1.6-4.4). Complications of colitis were the main cause of death in both groups. The cancer risk was related to extent of disease, duration of disease and female gender. Ten out of the 12 cases with cancer had or developed total colitis. However, only seven of the 134 cases with total ulcerative colitis and two of 87 cases with total indeterminate colitis developed cancer.