Risks of colorectal cancer and biliary cancer according to accompanied primary sclerosing cholangitis in Korean patients with ulcerative colitis: a nationwide population-based study

Background/Aims: We conducted a nationwide population-based study to investigate incidence rates of colorectal and biliary cancers according to accompanying primary sclerosing cholangitis in Korean ulcerative colitis patients. Methods: We used the Health Insurance Review and Assessment claim database from January 2007 to April 2020. Standardized incidence ratios of colorectal and biliary cancers in ulcerative colitis patients were calculated. Results: Among 35,189 newly diagnosed ulcerative colitis patients, 1,224 patients were diagnosed with primary sclerosing cholangitis. During the study period, 122 and 52 patients were diagnosed with colorectal and biliary cancers, respectively. Incidences of colorectal cancer were not higher in ulcerative colitis patients than those in the general population (standardized incidence ratios, 0.83; 95% confidence interval, 0.69-0.99), regardless of accompanied primary sclerosing cholangitis (standardized incidence ratio, 0.73; 95% confidence interval, 0.24-1.71). While incidences of biliary cancer were not higher in ulcerative colitis patients than those in the general population (standardized incidence ratio, 1.14; 95% confidence interval, 0.80-1.58), these were much higher with accompanied primary sclerosing cholangitis (standardized incidence ratio, 10.07; 95% confidence interval, 5.75-16.36). Cumulative incidences of colorectal and biliary cancers increased in patients who were diagnosed with ulcerative colitis at an older age. Conclusions: In Korean ulcerative colitis patients, colorectal cancer incidences were not higher than those in the general population regardless of accompanied primary sclerosing cholangitis. However, biliary cancer incidences were much higher in ulcerative colitis patients with primary sclerosing cholangitis than in those without, or in the general population.