Is there a sufficient evidence to confirm that physical activity decreases cancer risk and improves outcomes

Epidemiological data suggest that life style, including diet and physical activity — factors determining body mass, is associated with an increased risk of several cancers and with poor outcomes. Although most studies focus on obesity, there is also evidence that decreased physical activity alone may be a risk factor of cancer and predictor of poor prognosis. However, available data is limited to observational studies and few randomized trials assessing the impact of physical activity on endocrine, metabolic and infammatory biomarkers, which may be associated with cancer risk and outcomes. Observed association between physical activity and cancer could be biased and/or confounded. Data from randomized trials, which have cancer outcomes as primary end points is needed to conclude that increased physical activity is well documented method of cancer prevention and improves prognosis. With the lack of level one evidence such conclusion is not justified.