Strong evidence in support of CT colonography screening
Findings from the randomised controlled trial reported by Esther M Stoop and colleagues in The Lancet Oncology
provide important new data for adherence rates and overall programmatic yield for screening with optical colonoscopy and CT colonography. Particularly, results from this trial show a significant 55% improvement in screening participation with CT colonography over colonoscopy, which is a crucial component to the overall success of a screening programme. The overall programmatic yield (per invitee) for advanced neoplasia, which represents the optimum target of colorectal screening, was similar for CT colonography and colonoscopy. The somewhat lower yield of advanced neoplasia per patient assessed with CT colonography can be explained by the specific trial methods, most notably, the non-cathartic bowel preparation, the primary two-dimensional reading approach, and the different handling of small polyps (6—9 mm). When an approach of cathartic preparation with oral contrast tagging and primary three-dimensional reading is applied, CT colonography is equivalent or slightly better than optical colonoscopy for the detection of advanced neoplasia., An additional benefit of cathartic preparation for CT colonography is the ability to do same-day polypectomy, sparing the patient the need for repeat bowel preparation. Although only a small proportion of 6—9 mm adenomas are histologically advanced, lesions of this size were (appropriately) not sent for polypectomy in the colonography group of this trial, further decreasing its overall immediate yield. However, when the analysis of the comparative yield is restricted to cancers and large advanced adenomas, which are vastly more relevant to clinical outcomes than benign sub-centimetre polyps, CT colonography has the edge over colonoscopy. In terms of cancer detection, a meta-analysis reported a 100% sensitivity for CT colonography when a cathartic preparation with contrast tagging was used, and a slightly greater overall sensitivity than that with colonoscopy (96·1% vs
94·7%) when all colonography techniques were included.