Background & aims: Patients with ulcerative colitis are at increased risk of colorectal cancer. It is widely believed that this is secondary to colonic inflammation. However, the severity of colonic inflammation has never been shown to be a risk factor.
Methods: We devised a case-control study of patients with long-standing extensive ulcerative colitis to examine various potential risk factors for neoplasia. All cases of colorectal neoplasia detected from our surveillance program between January 1, 1988, and January 1, 2002, were studied (n = 68). Each patient was matched with 2 control patients from the same surveillance population (n = 136). Matching was for sex, colitis extent, age at onset, duration of colitis, and year of index surveillance colonoscopy. Segmental colonoscopic and histological inflammation was recorded by using a simple score (0, normal; 1, quiescent/chronic inflammation; and 2, 3, and 4, mild, moderate, and severe active inflammation, respectively). Other data collected included history of primary sclerosing cholangitis, family history of colorectal cancer, and smoking and drug history (mesalamine 5-aminosalicylic acid, azathioprine, and folate).
Results: Univariate analysis showed a highly significant correlation between the colonoscopic (odds ratio, 2.5; P = 0.001) and histological (odds ratio, 5.1; P < 0.001) inflammation scores and the risk of colorectal neoplasia. No other factors reached statistical significance. On multivariate analysis, only the histological inflammation score remained significant (odds ratio, 4.7; P < 0.001).
Conclusions: In long-standing extensive ulcerative colitis, the severity of colonic inflammation is an important determinant of the risk of colorectal neoplasia. Endoscopic and histological grading of inflammation could allow better risk stratification for surveillance programs.