Just a little exercise dramatically improves a woman's chances of surviving breast cancer.

How little? Walking just one hour a week is enough to make a survival difference. Just a little more exercise — walking three hours a week at an average pace of 2 to 2.9 miles per hour — cuts the risk of dying from breast cancer in half.

The findings come from an analysis of long-term data on some 3,000 women with breast cancer. Michelle D. Holmes, MD, DrPH, assistant professor at Harvard Medical School, and colleagues report the study in the May 25 issue of the Journal of the American Medical Association.

"Women who did three to five hours of exercise per week had the most benefit. They were 50 percent less likely to die," Holmes tells WebMD. "Women with breast cancer have little to lose and much to gain from being physically active."

That's good news for women with breast cancer, says Anne McTiernan, MD, PhD, author of Breast Fitness: An Optimal Exercise and Health Plan for Reducing Your Risk of Breast Cancer. McTiernan is director of cancer prevention at Fred Hutchinson Cancer Research Center.

"Women don't have to become athletes. They just have to get up and get moving," McTiernan tells WebMD. "Of course, we advise them to start slowly. Most women are debilitated after cancer treatment, so they need to take it easy at first as they become active again."

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Vigorous Exercise Not Bad — but Not Necessary

Holmes and colleagues found that compared with women who did not get at least an hour of walking each week:

—Women with 1 to 3 hours of weekly walking cut their risk of breast cancer death by 20 percent.

—Women with 3 to 5 hours of weekly walking cut their risk of breast cancer death by 50 percent.

—Women with 5 to 8 hours of weekly walking cut their risk of breast cancer death by 44 percent.

—Women with more than 8 hours of weekly walking cut their risk of breast cancer death by 40 percent.

Click here for Web MD's coverage of the breast cancer gene.

Holmes notes that there is no reason for women with breast cancer to avoid vigorous physical activity if they enjoy it.

On the other hand, women should be encouraged to hear that moderate exercise has maximum benefits, says Pamela N. Munster, MD, assistant professor at Tampa's H. Lee Moffitt Cancer Center.

"I don't want women with breast cancer to think, 'There is no way in hell I can do that,'" Munster tells WebMD. "Everyone can walk a couple of times a week. It is highly encouraging to see you can do moderate exercise and see a benefit for breast cancer."

And simple survival isn't the only benefit.

"We know from other studies that physically active women with breast cancer have better mood, better body image, and better self-esteem," Holmes says. "And this level of exercise fights heart disease and diabetes — which women with breast cancer can still get."

McTiernan notes that women should not wait until they have breast cancer to become physically active. Moderate exercise, she notes, cuts a woman's risk of getting breast cancer in the first place.

Click here for Web MD's coverage of life after surviving breast cancer.

By Daniel J. DeNoon, reviewed by Michael W. Smith, MD

SOURCES: Holmes, M.D. The Journal of the American Medical Association, May 25, 2005; vol 293: pp 2479-2486. Michelle D. Holmes, MD, DrPH, assistant professor, Harvard Medical School; associate physician, Brigham and Women's Hospital, Boston. Pamela N. Munster, MD, assistant professor, H. Lee Moffitt Cancer Center, Tampa, Fla. Anne McTiernan, MD, PhD, director, prevention center, Fred Hutchinson Cancer Research Center; professor of medicine and public health, University of Washington, Seattle; author, Breast Fitness: An Optimal Exercise and Health Plan for Reducing Your Risk of Breast Cancer.