Inflammatory Bowel Disease (IBD) is a condition characterized by chronic inflammation of the intestines. The two most common types of IBD are Crohn’s Disease (CD) and Ulcerative Colitis (UC). Although the overall risk of colon cancer in IBD is only 95 cases per 100,000 – this is much higher than for the general population.
In IBD, the main risk factors for colon cancer are the amount of intestine involved as well as the duration of the disease. It’s been estimated that patients with extensive UC have about a 2.5% increased risk of colon cancer. This increased risk is seen after eight to ten years of disease. This can increase up to 20% after thirty years of disease. Ulcerative Colitis, limited to the left side of the colon, also carries a high risk of colon cancer even though this higher risk is not seen until after 15 years of disease. Crohn’s Disease also carries a higher risk CRC after seven years of disease. Both Crohn’s Disease and UC patients should be screened for colon cancer with colonoscopy every one to two years starting seven years after disease duration.
Cancer in IBD is typically seen in areas of chronic inflammation, which can lead to an abnormal cell growth of colon cells called dysplasia. Dysplasia is known to be a precursor to colon cancer. Detecting dysplasia by colonoscopy has been shown to be an effective manner for preventing deaths in IBD. Dysplasia can be found in both colonic growths as well as a normal appearing colon. This means that frequent biopsies need to be taken throughout the colon in order to try to detect dysplasia. Furthermore, a confirmed finding of dysplasia should lead to a total removal of the colon as there is no way to determine if there is cancer away from an area of dysplasia.
The goal of colonoscopy in IBD is to detect dysplasia. An endoscopist must take multiple biopsies during the procedure in order to get an adequate sampling of the colonic mucosa. It takes up to 33 biopsies to detect dysplasia with a 90% confidence. Besides multiple random biopsies, there are other techniques that can help detect dysplasia including the use of jumbo forceps in order to obtain large biopsies for pathology analysis. Another aid that can be used to better detect dysplasia is chromoendoscopy. This refers to the topical application of temporary stains to better characterize inflammatory changes within the colon. The most commonly used stain, indigo carmine, has been shown to be more effective that a random biopsy protocol in detecting dysplasia.
In conclusion, the presence of IBD carries a high risk for the development of colon cancer. Frequent screening colonoscopy with multiple biopsies is an effective way to prevent the development of colon cancer, and should be standard of care for any patient with IBD.