Colitis-associated cancer in inflammatory bowel disease and effective endoscopic surveillance programs

Patients with longstanding inflammatory bowel disease, such as ulcerative colitis and Crohn's disease are well known to have at high risk of developing colorectal cancer. Oxidative stress-induced DNA damage from chronic inflammation is considered to cause various genomic and epigenomic changes in the intestinal mucosa (e.g., TP53 mutation, microsatellite instability and the methylation of the CpG islands) and the accumulation of such changes may lead to the development of dysplasia in the normal mucosa, which finally grows to become carcinoma. This model of carcinogenesis is called "the dysplasia- carcinoma sequence" of colitis-associated cancer. Surveillance colonoscopy with random biopsy has previously been recommended for the detection of early-phase tumors, which are generally faint and difficult to identify. However, targeted biopsy with chromoendo- scopy has been proposed because of its less invasive nature and cost effectiveness. A randomized controlled trial comparing random and targeted biopsy methods was conducted in Japan and targeted biopsy was shown to be almost comparable to random biopsy in terms of the rate of dysplasia detection. To enable more effective surveillance colonoscopy, the appropriate selection of high-risk patients and biopsy methods are important to allow lesions to be correctly detected.