Exercise Cuts Breast Cancer Risk

Study finds significant benefits for postmenopausal women.

By Amanda Gardner
HealthDay Reporter
Tuesday, December 12, 2006; 12:00 AM

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TUESDAY, Dec. 12 (HealthDay News) -- Postmenopausal women who engage in more vigorous physical activity seem to have a lower risk of breast cancer.

The beneficial effect was most pronounced for estrogen receptor positive/progesterone receptor negative tumors, which are generally more aggressive.

"It seems like another confirmation to the fact that exercise will help reduce the risk of breast carcinoma and may play some other interesting roles in addition to effects on cardiovascular health," said Dr. Jay Brooks, chairman of hematology/oncology at Ochsner Health System in Baton Rouge, La.

While overweight and obesity are risk factors for breast cancer, the findings also suggest that additional mechanisms may be involved in promoting the growth of tumors.

The association between exercise and a reduced risk of breast cancer is not a new one. Previous studies have shown that physical activity can reduce the risk for the disease among women of all ages.

But because breast cancer is such a varied disease, there may be different risk factors, depending on different tumor characteristics, including estrogen receptor (ER) and progesterone receptor (PR) status. Receptor status refers to whether these hormones bind to the surface of the tumor.

Only three small studies have looked at the association between physical activity and postmenopausal breast cancer defined by receptor status, the study authors said.

The new study, called the Iowa Women's Health Study, is the largest study to cross-classify estrogen receptor (ER) and progesterone receptor (PR) status, said Dr. James Cerhan, senior author of the study and professor of epidemiology at the Mayo Clinic College of Medicine in Rochester, Minn. The findings are published in the Dec. 11/25 issue of Archives of Internal Medicine.

Cerhan and his colleagues looked at 41,836 postmenopausal women who were between the ages of 55 and 69 in 1986. The participants filled out a 16-page questionnaire at the beginning of the study about their recreational physical activity and then were monitored for 18 years.