Reduction of the individual cancer risk by physical exercise.

The great variety of different types of human malignancies and the equally variable individual history of physical activity militate against finding any simple relationship between the risk of developing cancer and physical activity. Due to an obvious lack of prospective randomized trials, any evidence for a correlation is currently based on cohort and case control studies. Furthermore, the study results are sometimes inconsistent, and only for selected cancers, the available data are sufficient to draw any conclusions, resulting in a level of evidence of 2-3 (level of recommendation 'B'). Thus, a convincing risk reduction was found for colon cancer (40-50%) and estrogen-dependent malignancies such as breast (40-50%) and endometrial cancer (35-40%). Risk reduction is likely for some others, e. g. ovarian, lung or prostate cancer; but no definite conclusions can be drawn for hematological malignancies. Plausible explanations for reduction of the individual's cancer risk by increased physical activity are currently available for estrogen dependent cancers (breast, ovarian, endometrial) and colon cancers. The currently available data allow the recommendation of adopting a 'healthy life style' including physical activity for prevention of certain cancers.