The study involved 121 postmenopausal women who were taking aromatase inhibitors for breast cancer and who rated their joint pain as mild or greater on a standard pain-evaluation questionnaire. Sixty-one of them were randomly assigned to participate in two supervised strength training sessions a week and to engage in an average of 150 minutes of aerobic exercise a week. The others followed their normal daily activities.

After a year, joint pain scores decreased by 20 percent among the women in the exercise group and by three percent in the other group. The severity of joint pain also decreased significantly more in those who exercised than in those who didn't, as did the degree to which pain interfered with their lives.

"This is one of the first studies to identify an approach -- particularly a non-medical approach -- that can effectively lower joint pain for these patients," says the study's senior author, Jennifer Ligibel, MD, of the Susan F. Smith Center for Women's Cancers at Dana-Farber. "Exercise offers an attractive option for patients who want to continue taking these drugs but who are burdened by their side effects."

Aromatase inhibitors are recommended for all postmenopausal women with breast cancer categorized as hormone receptor-positive, meaning the cancer cells grow and divide in response to estrogen. The drugs, which prevent other hormones from being converted into estrogen, can reduce the risk of a cancer recurrence.

"Joint pain, or arthralgia, which occurs in up to half of breast cancer patients who take aromatase inhibitors, is one of the major drawbacks of these drugs," Ligibel states. "The pain leads many to discontinue the drugs, which can increase the chance that the cancer will return. Identifying a way to help women tolerate these drugs is a very important finding."