Increased risk of cancer in ulcerative colitis: a population-based cohort study.

Objective: There is an increased risk of colorectal cancer among patients with ulcerative colitis (UC). However, the overall and site specific cancer risks in these patients have been investigated to a limited extent. To study the association between UC and cancer, a population-based study of 1547 patients with UC in Stockholm diagnosed between 1955 and 1984 was carried out.
Methods: The patients were followed in both the National Cancer Register and the National Cause of Death Register until 1989. For comparisons, regional cancer incidence rates in Stockholm County were used together with individually computed person-years at risk in the UC disease cohort.
Results: A total of 121 malignancies occurred among 97 individuals as compared with 89.8 expected (standardized morbidity ratio [SMR] = 1.4; 95% confidence interval (CI), 1.1-1.6). Overall, an excess number of colorectal cancers (SMR, 4.1; 95% CI, 2.7-5.8), and hepatobiliary cancers in men (SMR = 6.0; 95% CI, 2.8-11.1) associated with primary sclerosing cholangitis, was observed. The risk of pulmonary cancer was decreased (SMR = 0.3; 95% CI, 0.1-0.9). In all, 91 extracolonic malignancies were observed, compared with the 82.3 expected (SMR = 1.11; 95% CI, 0.9-1.3).
Conclusions: In UC patients, the overall cancer incidence is increased mainly because of an increased incidence of colorectal and hepatobiliary cancer. This increase is partly counterbalanced by a decreased risk of pulmonary cancer compared with that in the general population.