Our experts highlight the most important research articles across the spectrum of topics relevant to the field of colorectal cancer

Abstract

Several studies over the past couple of years have indicated that colonoscopy is more efficacious in protecting against left-sided (or distal) compared with right-sided (or proximal) colorectal cancer. This is generally viewed as being a consequence of either an inadequate quality of endoscopic examination or biological differences between the proximal and distal colon. To gain insight into this issue, BurnettHartman et al. conducted a case–control study of advanced adenomas and sessile serrated polyps (SSPs) in patients who had undergone an earlier index colonoscopy. Advanced adenomas have a significant role in cancer development and are typical targets of endoscopy; SSPs have been recently described as precursors of a subset of colorectal cancers, and occur predominantly in the proximal colon. The study involved over 2000 participants who had had an index colonoscopy between 1998 and 2007. Previous endoscopy was found to be inversely associated with advanced adenomas in both the distal colon/rectum (overall response [OR]: 0.38; 95% CI: 0.26–0.56) and the proximal colon (OR: 0.31; 95% CI: 0.19–0.52). However, no associations were observed between previous endoscopy and SSPs (OR: 0.80; 95% CI: 0.56–1.13). Thus, there may be a disparity between advanced adenomas and SSPs with regard to their detection and removal. Alternatively, SSPs may develop much more rapidly than adenomas, so that their reoccurrence is more prevalent. In either case, the study by Burnett-Hartman et al. has significant implications for the issue of differential protection against proximal and distal colorectal cancer, and the overall utility of colonoscopy in preventing colorectal cancer.