Past studies have shown that exercise can reduce a woman's risk of getting breast cancer. But researchers wanted to know if exercise could also help women who already have breast cancer, by reducing their risk of death. They found that exercise can help.
One woman whose health was helped by exercise is Susan de Vries, a 43-year-old mother of three. She is in great physical shape, considering that four years ago, she was diagnosed with breast cancer.
"After my mastectomies, [I] got right out there and started walking pretty much right away. I mean, I remember one week after my surgery, walking. I was staying at my parents,' walking down my parents' driveway, very proud of myself that I made it that far," she said.
Now Susan exercises about four hours a week. A new study in the Journal of the American Medical Association says this activity could cut her risk of dying from breast cancer in half.
"Women with breast cancer who walked three to five hours per week were 50-percent less likely to die from breast cancer compared to inactive women with breast cancer," said physician Michelle Holmes of Brigham and Women's Hospital in Boston, who is the lead author of the study. She and colleagues at the hospital studied about 3000 breast cancer patients, tracking their health and exercise habits for up to 18 years or, in several cases, until their deaths.
"Compared to the most inactive women, just about any amount of physical activity was linked with a lower risk of death from breast cancer," she explained.
But that does not mean breast cancer patients have to become serious athletes.
"If you had asked me before this study, I would have guessed that perhaps more exercise, more benefit, but we did not find that. Women do not have to run marathons to gain the maximum benefit. We found that women who performed activity at the level of walking three to five hours per week gained the most benefit," she added.
There are several reasons why exercise might have this effect. It reduces levels of fat and the female hormone estrogen, which have been linked to breast cancer.
"Physical activity most benefited women who had the kind of cancer that is responsive to hormone levels, and that is the most common kind."
Exercise also bolsters the immune system, which fights disease.
Whatever the reason exercise helps, Ms. de Vries says it makes her feel much better. "I am fighting for my life. It is such an uplifting part of my life that I think the day I can no longer exercise will be a sad one," she said.
Dr. Holmes emphasizes that all the women in the study received standard treatment for breast cancer and that exercise is not a substitute for such treatment.