Background: Colorectal cancer is a complication of longstanding inflammatory bowel disease. The association between cancer and inflammation is best documented in ulcerative colitis, but an increased risk of cancer is also found in patients with Crohn's disease. Surveillance with colonoscopy is commonly used to detect dysplasia and early cancer in patients with in ulcerative colitis. There has been an increased focus on chemoprevention during the last decade.
Material and method: This paper is based on literature retrieved through non-systematic searches of the PubMed and Cochrane databases.
Results and interpretation: Several recent studies indicate that the incidence of colorectal cancer in patients with ulcerative colitis is lower than previously shown; in some population-based studies it does not exceed that in the general population. Extensive use of 5-aminosalicylates (5-ASA) explains a substantial part of the declining risk. The effect of surveillance colonoscopy has not been documented through prospective and randomized studies. Several studies have shown an increased risk of colorectal cancer and cancer in the small bowel in patients with Crohn's disease. No evidence supports that treatment with 5-ASA reduces the risk of colorectal cancer in patients with Crohn's disease, or that regular use of surveillance colonoscopy reduces the risk of cancer or mortality in patients with longstanding chronic inflammatory disease.