PT - JOURNAL ARTICLE AU - Leandro Fórnias Machado de Rezende AU - Thiago Hérick de Sá AU - Georgios Markozannes AU - Juan Pablo Rey-López AU - I-Min Lee AU - Konstantinos K Tsilidis AU - John P A Ioannidis AU - José Eluf-Neto TI - Physical activity and cancer: an umbrella review of the literature including 22 major anatomical sites and 770 000 cancer cases AID - 10.1136/bjsports-2017-098391 DP - 2018 Jul 01 TA - British Journal of Sports Medicine PG - 826--833 VI - 52 IP - 13 4099 - http://bjsm.bmj.com/content/52/13/826.short 4100 - http://bjsm.bmj.com/content/52/13/826.full SO - Br J Sports Med2018 Jul 01; 52 AB - Objective To provide an overview of the breadth and validity of claimed associations between physical activity and risk of developing or dying from cancer.Design Umbrella review.Data sources We searched Medline, Embase, Cochrane Database and Web of Science.Eligibility criteria for selecting studies Systematic reviews about physical activity and cancer incidence and cancer mortality in different body sites among general population.Results We included 19 reviews covering 22 cancer sites, 26 exposure-outcome pairs meta-analyses and 541 original studies. Physical activity was associated with lower risk of seven cancer sites (colon, breast, endometrial, lung, oesophageal, pancreas and meningioma). Only colon (a protective association with recreational physical activity) and breast cancer (a protective association with overall physical activity) were supported by strong evidence and highly suggestive evidence, respectively. Evidence from endometrial, lung, oesophageal, pancreas and meningioma presented hints of uncertainty and bias in the literature (eg, not reaching P values<10-6) showing large between-study heterogeneity and/or not demonstrating a definite direction for the effect when 95% prediction intervals were considered. Four of the 26 meta-analyses showed small study effects and 4 showed excess significance.Conclusion Physical activity is associated with a lower risk of several cancers, but only colon and breast cancer associations were supported by strong or highly suggestive evidence, respectively. Evidence from other cancer sites was less consistent, presenting hints of uncertainty and/or bias.