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Investigators in Italy conducted a randomized, controlled trial comparing the effectiveness of computed tomographic colonography (CTC) and flexible sigmoidoscopy for colorectal cancer screening. Patients were invited by a personal letter signed by their general practitioner to a prefixed appointment for their randomly assigned procedure. Preprocedure preparations included a single enema for flexible sigmoidoscopy and a noncathartic protocol for CTC. Results were as follows:
Among 1956 total invitations, the participation rate was 30.4% for CTC versus 27.0% for flexible sigmoidoscopy.
Men were slightly more likely to accept CTC versus flexible sigmoidoscopy, but acceptance rates in women were similar for each test.
Rates of referral to colonoscopy based on findings were 10% for each test.
The rate of advanced neoplasia detection was not significantly different between CTC and flexible sigmoidoscopy (5.1% and 4.7%).
A higher rate of advanced neoplasia detection in the proximal colon for CTC (2.7% vs. 1.3% for flexible sigmoidoscopy) was offset by a higher detection rate in the distal colon for flexible sigmoidoscopy (4.1% vs. 2.9%).
Regge D et al. Comparing CT colonography and flexible sigmoidoscopy: A randomised trial within a population-based screening programme. Gut 2016 Apr 12; [e-pub]. (http://dx.doi.org/10.1136/gutjnl-2015-311278)
Comment
This study has limited direct relevance to the U.S. because of the unpopularity of flexible sigmoidoscopy as a screening test. However, it is likely to be cited in the never-ending discussion of colonoscopy versus CTC as a screening test, because it provides direct evidence that colonoscopy would be more effective than cathartic-free CTC for detection of advanced neoplasia in the left colon. This result is consistent with the Dutch randomized trial of colonoscopy versus CTC for screening, which showed higher rates of advanced neoplasia detection by colonoscopy per participating subject.