Joint pain linked to breast cancer drug not inflammatory arthritis or autoimmune disease

The findings of the study will be presented Nov. 9 at the 74th Annual Scientific Meeting of the American College of Rheumatology in Atlanta, Georgia.

For many post-menopausal women with breast cancer promoted by the hormone estrogen, AIs can dramatically reduce the risk of their cancer coming back. Doctors say the AIs must be taken for five years to gain the full benefit, however the development of joint complaints in up to 35 percent of women forces many of them to stop early.

"It's not clear why these joint symptoms occur, but we wondered if they could be related to inflammation or an autoimmune disease," says Victoria K Shanmugam, MBBS, MRCP, assistant professor in the Division of Rheumatology, Immunology and Allergy at Georgetown University Medical Center, who led the study. "Our research ruled out both."

The case-controlled study included 25 postmenopausal breast cancer patients with hand pain and no known autoimmune disease who were treated for their cancer at Georgetown Lombardi Comprehensive Cancer Center. Another 23 participants who were not receiving the drugs enrolled as a control group.

Subjects were evaluated after abstaining from non-steroidal anti-inflammatory drugs for 48 hours. Signs of inflammation from arthritis would reappear in that time frame, the researchers reasoned. They completed a health assessment questionnaire. The rheumatologist completed a history and physical, and disease activity score. Various blood tests were conducted and x-rays and ultrasounds of all participants' hands were performed.

The rheumatologist and radiologist did not know which participants were taking AIs and which were not.

"We did find 4 of 48 women with autoimmune disease -- 2 in each group -- that had previously been undiagnosed, but the frequency was similar both in women receiving AIs and those who were not receiving AIs," Shanmugam says. "We found that several patients in the control arm had a similar constellation of symptoms to those receiving AIs."

But Shanmugam and her team did not find any conclusive evidence from their tests of inflammatory arthritis in the women with breast cancer.

"Although our study helps to rule out inflammatory arthritis or autoimmune disease, we do not know why women using AIs have these musculoskeletal symptoms. Still, knowing that the drugs are not promoting inflammatory arthritis may be beneficial to a number of women," she concludes.

"It would be prudent to refer those experiencing joint pain to a rheumatologist to rule out a previously undiagnosed autoimmune disease, and so that we can help address the symptoms," Shanmugam says. "Since the syndrome doesn't appear to be related to inflammatory arthritis, women should be encouraged to stay on their medication so they can gain the full benefit from it."

The study was supported by funds from the Georgetown University Department of Medicine, Grant and the National Institutes of Health. Shanmugam's research is funded by the American College of Rheumatology, Research and Education Foundation, Physician Scientist Development Award and the National Center for Research Resources.

Claudine Isaacs, a co-author, is part of a speakers bureau for AstraZeneca, which makes an aromatase inhibitor.