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Screening with flexible sigmoidoscopy helps prevent cancers and deaths

BMJ 2012; 345 doi: http://dx.doi.org/10.1136/bmj.e8388 (Published 12 December 2012) Cite this as: BMJ 2012;345:e8388

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Screening 1000 middle aged adults with flexible sigmoidoscopy would prevent just under three colorectal cancers (2.8, 95% CI 1.4 to 4.0) and just over one death from colorectal cancer (1.2, 0.8 to 1.5), according to a meta-analysis of five large trials from Europe, Scandinavia, and the US. In pooled analyses, screening cut the incidence of colorectal cancer by 18% (relative risk 0.82, 95% CI 0.73 to 0.91) and mortality from colorectal cancer by 28% (0.72, 0.65 to 0.80), when compared with no screening or usual care.

The five included trials tested slightly different screening protocols, but most started with flexible sigmoidoscopy (usually once only) then moved on to full colonoscopy for adults with high risk findings, such as large or multiple polyps. In two trials, small polyps were removed at the initial screen. In others, all patients with disease were referred on for treatment. As expected, screening based on flexible sigmoidoscopy was best at preventing left sided cancers (3.0 (2.2 to 3.7) avoided cases per 1000 screened).

Pooled analyses add power and precision to estimates of benefit from individual trials, and the authors are now confident that this kind of screening can help prevent cancers and save lives (or at least prevent deaths from colorectal cancer). It is much less clear how screening with flexible sigmoidoscopy compares with primary use of colonoscopy, or faecal occult blood tests. Colonoscopy is already more popular in the US, say the authors. The meta-analysis did not report on possible harm from screening.

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Cite this as: BMJ 2012;345:e8388