When members of the general population were invited to participate in colon cancer screening, many more of them agreed to noncathartic computed tomographic colonography than to colonoscopy in a study published online Nov. 15 in the Lancet Oncology.
However, colonoscopy identified more advanced neoplasias than colonography did.
These two differences "more or less cancelled each other out" in terms of the diagnostic yield, said Dr. Esther M. Stoop of Erasmus University Medical Center, Rotterdam, and her associates.
These findings indicate that both noncathartic CT colonography and colonoscopy are appropriate for population-based screening, and other factors such as cost-effectiveness must be assessed to determine which method is preferable, the authors noted.
Dr. Stoop and her colleagues compared both the participation rate and the diagnostic yield of the two strategies among average-risk people aged 50-75 years in the general population residing in the areas around Amsterdam and Rotterdam. A total of 8,844 people were randomly assigned to be invited for screening colonoscopy (5,924 subjects) or CT colonography (2,920).
The noncathartic preparation method for CT colonography consisted of consuming small amounts of iodinated contrast agent.
Participation was markedly higher for noncathartic CT colonography (34%) than for colonoscopy (22%). The total number of invitees who participated was 1,276 for colonoscopy and 982 for CT colonography.
The final completion rates for the two procedures were similar, at 99% for CT colonography and 98% for colonoscopy. Initially, 4% of the CT colonography group had incomplete procedures because of inadequate distention, inadequate tagging, or both, but the procedure was successfully repeated in all but 11. Similarly, 3% of the colonoscopy group initially had incomplete procedures because of poor bowel preparation, pain during the procedure, bowel anatomy, colonic stricture, or other reasons, but the colonoscopy was successfully repeated in all but 28.
The diagnostic yield for all advanced neoplasia was significantly higher for colonoscopy: 8.7 per 100 colonoscopy subjects versus 6.1 per 100 CT colonography patients (P = .02). But when the data were analyzed another way, the diagnostic yield was 1.9 per 100 invitees for colonoscopy and 2.1 per 100 invitees for CT colonography; this difference was not statistically significant.
The diagnostic yield for advanced neoplasias of 10 mm or more, which included all cancers, was 1.5 per 100 invitees for colonoscopy and 2.0 per 100 invitees for CT colonography.
"Given the small number of colorectal cancers detected and the size of our study group, we were unable to obtain a precise comparison of the diagnostic yield for colorectal cancers," the investigators noted (Lancet Oncol. 2011 Nov. 15 [doi:10.1016/S1470-2045(11)70283-2]).
Postpolypectomy bleeding developed in two colonoscopy subjects and in three CT colonography patients when they were referred for colonoscopy because of suspicious lesions.
In addition, CT colonography identified potentially important extracolonic abnormalities in 107 subjects, including four renal cell carcinomas, one duodenal carcinoma, seven abdominal aortic aneurysms, and three smaller aneurysms.
The study was funded by the Netherlands Organisation for Health Research and Development, the Centre for Translational Molecular Medicine, and the Nuts Ohra Foundation. Study materials were provided by Guerbet, Philips Healthcare, and Norgine. The study authors stated that they had no conflicts of interest.