Physical activity and breast and colon cancer: Evidence-based physical activity

Aim. - Since last years, numerous studies have reported a significant association between prevention of some cancers (mainly, breast and colon cancer) and physical activity (PA). Current knowledge. - This is for colon cancer that the strength of evidence is the highest: 43 studies out of 51 have demonstrated that subjects with higher PA have a 40 to 50% decreased risk of developing colon cancer compared to sedentary subjects. For breast cancer, there is an inverse relationship between incidence of cancer and PA in postmenopausal women with a decreased risk of 20 to 80% depending on studies; for premenopausal women the association is weaker (15-20% decrease). Most of these studies show a dose-effect relationship, an increase in PA (greater than 3-4h of moderate intensity PA per week) being associated with a more important decrease on the risk of developing breast and colon cancer. Finally, in tertiary prevention, PA started after the completion of anticancer treatment decreases the risk of recurrence of 50-60% for both types of cancer. Conclusion. - The beneficial effects of PA are mediated through different interrelated mechanisms. (C) 2009 Elsevier Masson SAS. All rights reserved.