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Study: Exercise May Improve Breast Cancer Survival (dateline September 11, 2005)

A recent study finds that women who have been diagnosed with breast cancer can improve their chances of survival if they engage in light or moderate physical activity, such as walking a few hours a week. In the study, women who walked just one hour per week lowered their risk of dying from breast cancer, compared to women who exercised less than that amount, while women who walked 3 to 5 hours lowered their risk even more. Researchers say that the study results suggest an easy way that women can improve their chances of surviving breast cancer.

While past studies have shown that physical activity can decrease the incidence of breast cancer, the effect on recurrence or survival after a breast cancer diagnosis is not known. Therefore, Michelle D. Holmes, MD, PhD of Harvard Medical School and Brigham and Women's Hospital in Boston and her colleagues followed 2,987 female registered nurses who took part in the Nurses' Health Study. Each of the women had been diagnosed with stage I, II, or III breast cancer between 1984 and 1998. The researchers followed the women until death or June 2002, whichever came first.

After 10 years of following the women, Dr. Holmes and her colleagues found that women who exercised the equivalent of walking about 1 hour a week, at a 2-3 mile-per-hour pace, were less likely to die from breast cancer than women who exercised less. In addition, women who exercised the equivalent of walking about 3-5 hours per week at that pace were at the lowest risk of dying from breast cancer. Women who got more exercise also had a lower risk of dying, but not as low as women in the middle group. In all, 92% of the women who exercised 3-5 hours per week (or about half an hour per day) were still alive after 10 years, compared to 86% of those exercised less than one hour per week.

Based on the study results, the researchers concluded that "physical activity after a breast cancer diagnosis may reduce the risk of death from this disease. The greatest benefit occurred in women who performed the equivalent of walking 3 to 5 hours per week at an average pace, with little evidence of a correlation between increased benefit and greater energy expenditure. Women with breast cancer who follow U.S. physical activity recommendations may improve their survival."

However, the study only found positive results in women with estrogen-receptor (ER) positive breast cancers. About 80% of breast cancer patients have ER-positive breast cancer, which depend on estrogen for survival. Exercise can lower the levels of estrogen in the body. There were not many ER-negative breast cancer patients in the study, though, which may explain why the researchers did not see a similar benefit in these women.

The American Cancer Society (ACS) recommends that adults engage in at least moderate activity for 30 minutes or more on 5 or more days of the week. According to ACS, 45 minutes or more of moderate to vigorous activity on 5 or more days per week may further enhance reductions in the risk of breast and colon cancer. In addition, ACS recommends that men and women maintain a healthful weight throughout life by balancing caloric intake with physical activity and to lose weight if currently overweight or obese. Finally, alcohol, if consumed, should be used in moderation.

Research has also shown that exercise can reduce the side effects associated with breast cancer treatment. In a 2001 study, Roanne Segal, MD of the Ottawa Regional Cancer Centre in Ontario, Canada and her colleagues found that women who exercised by walking one hour or more three to five times a week had improved cardiovascular health and were able to function better after breast cancer treatment than the women who did not exercise. Click here for more information on this study.

Currently, the U.S. government-sponsored Women's Health Initiative study is investigating whether exercise can help prevent breast cancer. Results released in 2003 suggest that increased physical activity is associated with reduced risk for breast cancer in post-menopausal women; that the longer one exercise, the greater the benefit; and that exercise need not be strenuous. Click here for more information on this study.

Additional Resources and References

  • The study referenced in this article appeared in the May 25, 2005 issue of the Journal of the American Medical Association, Vol. 293, No. 20: 2479-2486,
  • The American Cancer Society provides information on nutrition, exercise, and cancer on its website at