Exercise improves post-cancer survival

Physical activity decreases disease-related and all-cause mortality rates in cancer survivors.

A dose-response effect was seen between increasing levels of activity and decreasing rates of mortality.

Physical activity appears to lower mortality rates in cancer survivors, particularly among those diagnosed with breast and colorectal cancer, according to a systematic review of 45
observational or randomized and controlled studies published between 1950 and August of 2011.

Results of the review, published in theJournal of the National Cancer Institute (2012;104:1-26), indicate that physical activity reduces all-cause, breast cancer-specific, and colon cancer-specific mortality. The randomized controlled trials that used biomarker endpoints suggest that exercise may be associated with positive changes in circulating insulin level, insulin-related pathways, inflammation, and, possibly, immunity.

The strongest evidence was found among those who survived breast cancer, followed by those who survived colorectal cancer. Approximately half of the studies reported a dose-response effect of decreasing mortality risk with increasing activity. None reported an association between increased activity and an increase in breast cancer deaths or deaths from any cause.

Additional research is needed before experts can make specific recommendations about the type, timing, duration, and frequency of exercise needed to make a difference, the authors write. Further, the studies defined “physical activity” in various ways, some using hours per week and others using times, units, or MET-hours per week. Insufficient evidence exists regarding whether physical activity reduces mortality for survivors of other cancers.

The authors also note that the studies thus far have not controlled for important confounders of the association between exercise and survival. For example, it is possible that subclinical metastasis manifesting as fatigue would make a woman less able to participate, or less interested in exercise, skewing who participates in physical activity.

Read other articles in this issue of Special Delivery