Cancer patients who keep fit may enjoy signficantly improved survival chances, researchers said yesterday.
As cancer survivors are now living longer, and often looking for lifestyle advice, Dr Rachel Ballard-Barbash at the US National Cancer Institute, based in Maryland, USA, and colleagues reviewed several studies on the relationship between physical activity and mortality.
Results from 27 observational studies showed "consistent evidence" that physical activity is linked to reduced all-cause, breast cancer-specific, and colon cancer-specific mortality.
But the researchers say: "There is currently insufficient evidence regarding the association between physical activity and mortality for survivors of other cancers."
Studies of cancer biomarkers suggest that "exercise may result in beneficial changes in the circulating level of insulin, insulin-related pathways, inflammation, and, possibly, immunity; however, the evidence is still preliminary".
Writing in the Journal of the National Cancer Institute, the authors say that future research needs to look at other types of cancer, have larger sample sizes, and to include other risk factor characteristics.
There is also a need to understand the biological mechanisms by which exercise affects survival following cancer, they add.
Commenting on the study, Dr Edward Giovannucci of the Harvard School of Public Health, Boston, USA, points out: "Few other leads have shown as much promise as physical activity in extending the lives of cancer survivors."
He says: "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."
Physical Activity, Biomarkers, and Disease Outcomes in Cancer Survivors: A Systematic Review. Ballard-Barbash, R. et al. The Journal of the National Cancer Institute May 8 2012 doi: 10.1093/jnci/djs207
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