The effects of bariatric surgery on colorectal cancer risk: systematic review and meta-analysis.

Obesity is an established risk factor for colorectal cancer (CRC) but the effects of bariatric surgery on CRC incidence are uncertain. A systematic review of six electronic databases identified 3691 articles. Four observational studies met our inclusion criteria and results were pooled using a random effects model. Meta-analysis of these four studies revealed that bariatric surgery was associated with a significantly (p = 0.004) lower CRC incidence (RR = 0.73, 95 % confidence interval, 0.58 - 0.90) when compared with obese non-operated individuals, i.e., bariatric surgery is associated with a 27 % lower CRC risk. However the evidence base is limited and these findings should be confirmed by future studies with improved designs.