Strategies for detecting colon cancer and/or dysplasia in patients with inflammatory bowel disease

Patients with long-standing ulcerative colitis and colonic Crohn's disease have an increased risk of colorectal cancer compared with the general population. This review shows that there is no conclusive evidence that surveillance colonoscopy prolongs survival in these patients. However, since the principal studies were completed it has become clear that numerous biopsies are needed to accurately identify pre-cancerous lesions (dysplasia) and that the benefit of surveillance could have been greater if multiple biopsies had been performed. It has also since been demonstrated that targeted biopsy of dysplastic areas is enhanced by dye spraying at colonoscopy. There is evidence from case control studies that cancers tend to be detected at an earlier stage in patients who are undergoing surveillance and that these patients have a better chance for recovery. This evidence should be treated with caution since lead-time bias (the period between early detection of disease and the time of its usual clinical presentation) may contribute substantially to this apparent benefit. It is unlikely that there will be a randomised trial of surveillance colonoscopy in patients with colitis. Lower quality evidence, however, supports the continued use of some form of surveillance for these patients. The nature of this surveillance is gradually evolving, with two important developments since the last version of this review in 2004. Firstly, it has become apparent that most pre-malignant (dysplastic) lesions can be visualised with careful endoscopy. Secondly, patients who lack histological inflammation on colonoscopy are at low risk for cancer development.