Photo by Stephanie Cartier
To the seemingly endless list of benefits that come from regular exercise, researchers are adding one more reason to get out and get moving. Dr. Page Abrahamson, a postdoctoral researcher in the Public Health Sciences Division, led a study recently that found overweight breast-cancer patients who were physically active in the year before diagnosis had increased five-year survival rates.
In the Oct. 15 issue of Cancer, the peer-reviewed journal of the American Cancer Society, study author Abrahamson reports that the level of exercise in the year prior to breast-cancer diagnosis affects patients' ability to survive after a diagnosis.
Abrahamson conducted the study as a doctoral student in the University of North Carolina at Chapel Hill's School of Public Health. To measure the effects of physical activity on breast-cancer survival, Abrahamson and her colleagues followed 1,264 women aged 20 to 54 who had been diagnosed with breast cancer between 1990 and 1992. Interviewers asked participants to report the nature and frequency of exercise they did at ages 12 to 13, 20 and in the year prior to diagnosis.
Researchers weren't surprised to find that physical activity increased the odds of surviving breast cancer, but what did surprise them was that the most crucial activity occurred in the year immediately before diagnosis, not an average over a lifetime.
"We were not able to evaluate detailed, long-term exercise," Abrahamson said in a news release. "However, exercise levels in the year before diagnosis is likely an indicator of a person's average adult exercise patterns."
The study shows a benefit only for women with a body-mass index of 25 or higher, which is overweight. Researchers point out that studies on the effect of exercise and survival rates after diagnosis are limited — most research focuses on how exercise prevents cancer — and further study is needed. "Research focusing on survivorship is definitely growing," Abrahamson said. "Survival has traditionally focused on the tumor characteristics, such as the stage and grade of the cancer, and more recently, clinicians and researchers have realized there are likely other factors involved, such as lifestyle factors."
Women with a BMI of 25 or higher in the top 25th percentile in terms of exercise were 21 percent more likely to survive a breast-cancer diagnosis over the nine-year study period than those in the lowest quartile. But even for woman not in the top quartile, there is an increased benefit. For overweight or obese women with high levels of exercise prior to diagnosis, chances of survival were 30 percent higher than those who reported low levels of activity.
Abrahamson said physical activity might influence breast-cancer outcomes in the same way it affects the odds of developing breast cancer. Benefits of increased exercise include decreased estrogen exposure, enhanced immune function, lower body fat or reduced insulin resistance, all of which are key in preventing breast cancer.
"Disease stage and tumor grade are estimated to explain only about 20 percent of variation in survival. Identifying other factors that affect prognosis will help us identify women at increased risk of death and provide more ways for patients to enhance their survival," Abrahamson said.
Determining which lifestyle factors play a role in survival will likely continue to be studied, since more and more women are living longer and better after surviving breast cancer, and many of them are pushing for more research. "This study is a good step for encouraging additional studies to look more specifically at different types and amounts of physical activity, and how that may impact survival," Abrahamson said.
Funding for this study came from the National Cancer Institute and Public Health Service grants from the National Institutes of Health.
Dr. Peggy Porter of the Center's Human Biology Division is a co-author on this study. Other co-authors are from: Emory University, Atlanta, Ga.; Mount Sinai School of Medicine, New York, N.Y.; the federal Centers for Disease Control and Prevention, Atlanta, Ga.; and the National Cancer Institute, National Institutes of Health, Bethesda, Md.