Rachel Ballard-Barbash, M.D., of the Applied Research Program in the Division of Cancer Control and Population Sciences at the National Cancer Institute and her team reviewed 45 articles of observational studies and randomized controlled trials (RCTs), published between January 1950 and August 2011, that examined the relationship between physical activity and cancer mortality and/or cancer biomarkers amongst those who survived the disease. They discovered that the RCTs with biomarker endpoints indicate that exercise is potentially beneficial in terms of the survivors' insulin levels and also reduces inflammation and may improve immunity.
The strongest evidence was found in those who survived breast cancer, followed by those who survived colorectal cancer. Most studies displayed a statistically considerably decreased risk of breast cancer and all-cause mortality related to exercise.The researchers highlight the fact that due to the diversity of the various studies, specific recommendations in terms of exercise types or timing cannot be made, however, they do confirm that exercise contributes to the cancer survivors' overall safety and to their physical and mental benefits.
They continue saying that future RCTs should examine various types of exercise, including how obesity, weight loss and cancer treatments may impact the effects of exercise on biomarkers, as well as how exercise may influence comorbidities in cancer survivors.
Edward L. Giovannucci, M.D., ScD, of the Department of Nutrition at the Harvard School of Public Health writes in a linked article that physical activity may prolong cancer survivor's life span and their quality of life, writing:
"Even though direct effects of physical activity on cancer are not definitely proven, given that physical activity is generally safe, improves quality of life for cancer patients, and has numerous other health benefits, adequate physical activity should be a standard part of cancer care."