The risk of colorectal cancer in patients with inflammatory bowel diseases in Finland: a follow-up of 20 years.

Background and aims: Data on the relative risk of colorectal cancer in inflammatory bowel diseases (IBD) are inconsistent. To prevent the development of cancer, endoscopic facilities should be targeted correctly. We report here the results of a 20-year follow-up in Finland and evaluate the efficacy of endoscopic surveillance in cancer prevention. Methods: The data were based on an IBD register in our catchment area in 1986–2007. The population-based cohort comprised 1915 patients, 1254 with ulcerative colitis, 550 with Crohn's disease and 111 with inflammatory bowel unclassified. Colorectal cancer cases were obtained from the IBD register; the colorectal cancer figures in the respective population were obtained from the Finnish Cancer Registry. Results: Colorectal cancer was found in 21 patients, the standardized incidence ratio (SIR) being 1.83 (95% confidence interval (CI) 1.13–2.79) for IBD. Colorectal cancer risk was 3.09 (CI 1.50–5.75) for extensive UC, and 3.62 (CI 2.00–11.87) for Crohn's disease affecting the colon. Eleven (52%) of the colorectal cancer cases were TNM stage 3 or 4. In the same observation period 10 colectomies with ileoanal anastomosis were performed with the indication of cancer risk in ulcerative colitis; of these 10 patients only two had no additional risk factors for colorectal cancer, for example primary sclerosing cholangitis, pseudopolyposis or active disease. Conclusions: The risk of colorectal cancer in the cohort was only moderately increased. In the absence of additional risk factors, endoscopic surveillance was of limited benefit. We therefore suggest intensive endoscopy surveillance to be targeted on patients with definite risk factors.