CANCER AND INFLAMMATORY BOWEL-DISEASE - BIAS, EPIDEMIOLOGY, SURVEILLANCE, AND TREATMENT

Individuals with chronic ulcerative colitis are at increased risk of d eveloping colorectal carcinoma, particularly if there is long-standing disease or extensive colitis, It is generally accepted that the risk of colorectal cancer does not begin until 8 to 10 years after the time of diagnosis of ulcerative colitis, Thereafter it increases by approx imately 0.5% to 1.0% per year, In patients with Crohn's disease, the r isk of malignancy is smaller and less well defined. The most significa nt predictor of the risk of malignancy in patients with inflammatory b owel disease is the presence of dysplasia in colonic biopsies. There i s considerable controversy in the literature regarding the efficacy of colonoscopic surveillance programs and the role of prophylactic surge ry to prevent colorectal cancer. Surveillance certainly fails to detec t carcinoma in some patients who are having regular colonoscopy. Conce rns have also been raised as to the cost-benefit of colonoscopic surve illance in patients with colitis. Randomized controlled trials of surv eillance programs are highly unlikely in view of the low prevalence of IBD in the population, the long period of observation required, and t he probability of contamination of surveillance programs by colonoscop y for assessment of disease activity, Despite the lack of clear guidel ines, surveillance colonoscopy and biopsy continues to be widely pract iced, Research is proceeding to identify genetic and biochemical marke rs that may prove clinically useful for predicting cancer risk At pres ent, however, surveillance programs are likely to continue according t o institutional practice. It is important for those participating in s uch programs to be aware of the limitations of colonoscopy and biopsy as a means of reducing the risk of cancer in inflammatory bowel diseas e.