Activité physique et cancer

Several studies published over the recent years have shown an association between prevention of certain type of cancer (mainly breast and colon cancer) and physical activity (PA). A large number of evidences support the beneficial effect of PA in the prevention of colon cancer: among the 51 studies on colon and colorectal cancer, 43 have demonstrated a risk decrease in subjects with the most intense PA, a 40-50% mean risk decrease. With regard to breast cancer, studies have shown an inverse association between PA and breast cancer in menopausal women, a 20-80% risk reduction depending on studies; in non menopausal women, this association is less marked (a 15-20% reduction). Furthermore, most studies report a dose-effect relationship, an increase in the PA level (> 3-4 h/week of a moderate intensity PA) being associated with a greater reduction in the risk of occurrence of breast or colon cancer. Last, in tertiary prevention, PA initiated soon after cancer treatment, reduced the risk of cancer relapse, by 50-60% for breast cancer and colon cancer. The beneficial effects of PA are dependent of multiple interrelated mechanisms.