Aromatase inhibitors (AI), popular breast cancer drugs, can be continued to be used safely as these drugs do not carry any risk of inflammatory arthritis or autoimmune disease.
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 said 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. Our research ruled out both," said Victoria K Shanmugam, of the Georgetown University Medical Center, who led the study.
The case-controlled study included 25 postmenopausal breast cancer patients with hand pain and no known autoimmune.
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.
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.
"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.
"We found that several patients in the control arm had a similar constellation of symptoms to those receiving AIs," said Shanmugam.
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 concluded.
The findings would be presented at the 74th Annual Scientific Meeting of the American College of Rheumatology in Atlanta, Georgia.