From Science Daily
"Many treatments may increase survival, but at a cost of quality of life; physical activity may not only extend life but may also enhance its quality. Given that physical activity is generally safe and has numerous other health benefits, adequate physical activity should be a standard part of cancer care."
Edward Giovannucci, epidemiologist at the Harvard School of Public Health, advanced this opinion a few weeks ago in the Journal of the National Cancer Institute [J Natl Cancer Inst. 2012 Jun 6;104(11):797-9.] in relation to a general article published in the same edition of that journal. In that article Rachel Ballard-Barbash of the National Cancer Institute summarised 45 studies on the effect of physical activity on cancer survivors. [J Natl Cancer Inst. 2012 Jun 6;104(11):815-40.]
Ballard-Barbash concluded that almost all of the studies reported that cancer survivors live longer if they are physically active. The figures below summarise the results of studies of women with breast cancer, the most fully researched form of cancer.
The table first shows the effect of physical activity on death by breast cancer and then on death in general. Breast cancer survivors who were physically active before they were diagnosed with breast cancer had a higher survival rate than did women who were physically less active. However, an important factor is physical activity after the diagnosis.
Similar figures, but then in relation to other forms of cancer, can be found [here] en [here]. Once again, physical activity increases the chances of survival.
The general study shows that cancer survivors who want to improve their chances don't need to become fanatic sportsmen. "In our review, the most common activity was walking", Ballard-Barbash said in the New York Times. [nytimes.com May 16, 2012], "which happens to be an activity that is within the scope of almost anyone." Ballard-Barbash also advised cancer survivors who want more intense physical activity to first consult with their physician since some cancer treatments can damage the heart and circulatory system.
How physical activity helps cancer survivors is still a mystery, writes Giovannucci in his commentary. But it works extremely well. "Given the limited success that the most potent and cleverly designed drugs have had on cancer to date, why should something as seemingly simple as walking have potent anticancer activity?"
Giovannucci suggests two answers to that question. One answer is that physical activity makes people healthy, whether or not they have cancer. For example, physical activity is a medicine against diabetes, and cancer patients with diabetes die sooner than do those without diabetes. [JAMA. 2008 Dec 17;300(23):2754-64.] Eliminate the diabetes and the chances of survival increase.
The other answer is that physical activity has a direct effect on cancer cells. It's possible that muscles that move draw hormones such as insulin and IGF-1 from the blood and block hormones that stimulate the growth of cancer cells.
Organisations such as the American Cancer Society [CA Cancer J Clin. 2006 Nov-Dec;56(6):323-53.], the World Cancer Research Fund [Food, Nutrition, Physical Activity, and the Prevention of Cancer. Washington, DC: World Cancer Research Fund; 2007] en het American College of Sports Medicine [Med Sci Sports Exerc. 2010 Jul;42(7):1409-26.] concluded years ago that cancer survivors had to be physically active.
"The advice that I would have previously given to one of my patients would have been to 'take it easy'", said oncologist Jane Maher at Macmillan Cancer Support in an interview with the BBC. [bbc.co.uk 7 August 2011] "This has now changed significantly because of the recognition that if physical exercise were a drug, it would be hitting the headlines."
J Natl Cancer Inst. 2012 Jun 6;104(11):815-40.