Biological markers as an outcome measure of exercise in cancer rehabilitation: A systematic review

The number of people living with and beyond cancer is at an all time high. These survivors are not necessarily living well, as adverse side effects from cancer and its treatment can last up to 5 years and leave patients at a higher risk of developing secondary cancers and other chronic illnesses. Exercise has been proven to be a safe and effective method of intervention to decrease mortality and overall improve health outcomes. The biological mechanism through which this occurs is an area of research that is in its infancy and not well defined. A systematic search was conducted of four databases for relevant randomized controlled trials (RCTs) published between January 2004 and December 2014. Studies had to include any blood/urine biological markers as an outcome measure to a physical activity intervention for cancer survivors posttreatment. Fifteen relevant articles were identified (12 RCTs). It was shown that randomized controlled trials of exercise for cancer survivors posttreatment may results in changes to circulating levels of insulin, insulin related pathways (insulin like growth factor II [IGF II], IGF binding protein 3), high density lipoprotein, total cholesterol, leptin, and osteocalcin. Due to small sample sizes, the evidence is still preliminary and therefore more research is warranted in this area in the form of larger, statistically powered RCTs for cancer survivors.