Physical activity decreases cancer risk.  Exercise may help prevent the development of certain cancers, notably colon and breast, numerous studies show.
D001943:Breast Neoplasms / Q000517:prevention & control*; D003110:Colonic Neoplasms / Q000517:prevention & control*; D019317:Evidence-Based Medicine; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D040242:Risk Reduction Behavior