In a pair of studies published on the Journal of Clinical Oncology website http://www.jco.org/early_release/, and slated to appear in the journal's Aug. 1 issue, the researchers found that colon cancer patients engaging in moderate levels of exercise six to 12 months after completing therapy had an approximately 50 percent higher survival rate than those who didn't exercise. The improvement took place in patients with very early and more advanced (but non-spreading) colon cancer, all of whom had undergone surgery intended to cure the disease.
"From previous studies we know that regular physical activity reduces the risk of developing colon cancer, but until now few studies have looked at the survival effect of exercise on people who have been treated for disease," says the study's lead author, Jeffrey Meyerhardt, MD, MPH, of Dana-Farber. "While our work found a significant benefit for patients who exercise, it's important that exercise be seen as a supplement to, not a replacement for, standard therapies."
The two studies used different sets of data to arrive at their shared conclusion. One study involved 832 patients with stage III colon cancer (involving the lymph nodes around the tumor but with no signs of having spread outside the area) who had received surgery and follow-up chemotherapy as part of the Cancer and Leukemia Group B (CALGB) national clinical trial. Data on participants' recreational physical activities and health status was collected about six months after the completion of therapy.
Researchers found that patients who engaged in moderate physical activity - the equivalent of walking six or more hours a week at an average pace of 2-2.9 miles per hour - were 47 percent more likely to be alive and free of disease than those who were less physically active.
The other study involved 573 participants in the Nurses' Health Study, a project organized by Brigham and Women's Hospital which tracks the health of 121,700 female registered nurses by questionnaires mailed every two years. The nurses included in the current study had undergone surgery intended to cure stage I to III cancer at least six months earlier.
The results of this study mirrored those of the CALGB-based study. Additionally, patients who increased their physical activity from levels before diagnosis had an approximately 50 percent lower chance of dying, from colon cancer or any other cause, than those who remained physically inactive.
"The fact that two different sets of data have yielded such similar results encourages us about the validity of our findings," Meyerhardt remarks. "Although the data from the CALGB study did not include data on the participants' exercise levels prior to diagnosis with colon cancer, we do have that information for those in the nurses study. From that data, it appears that the amount of exercise prior to diagnosis doesn't affect the outcome of treatment. What matters is exercising after standard therapy has been completed."
Scientists do not have a definite physiological explanation for the benefit of exercise for colon cancer survivors, but they speculate it may be tied to a reduction in the body's production of insulin and a similar compound, insulin-like growth factor, which fuel the growth of some cancer cells.
"To reduce the chances that colon cancer will return after treatment, as well as for overall health reasons, regular exercise is a good option for survivors to consider," says Meyerhardt, who also is an assistant professor of medicine at Harvard Medical School. "As with any exercise program, people should check with their doctor before increasing their degree of physical activity."