Sept 7 : A new study has found that aches and pains caused due to side effects of a commonly prescribed breast cancer drug causes 13 percent of women to stop taking it.

The aromatase inhibitors, a type of drug designed to block the production of estrogen, which fuels some breast cancers, have been shown to be more effective than tamoxifen, and are generally given after surgery, chemotherapy or radiation therapy to prevent the cancer from returning.

However researchers at the University of Michigan Comprehensive Cancer Center found that a number of women discontinue with the medication due to the side effects.

“We know 25 percent to 30 percent of women taking aromatase inhibitors have aches and pains. What was surprising here was the number of people who actually discontinued the drugs because of the side effects. Up to 15 percent of patients in previously reported studies stopped taking aromatase inhibitors for a variety of reasons, but in our study, we had 13 percent drop out just because of musculoskeletal problems,” says N. Lynn Henry, M.D., Ph.D., lecturer in internal medicine at the U-M Medical School.

As a part of the study, women were assigned to take one of two aromatase inhibitors, exemestane or letrozole, and were followed for at least six months.

Study participants completed questionnaires about their health and side effects. If their reported joint and muscle concerns scored above a certain threshold on these questionnaires, the women were referred to a rheumatologist. Referrals were based on worsened pain or a change in function from the start of the study that resulted in more difficulty performing tasks such as rising from a chair, climbing out of a car or opening a jar.

The researchers are looking at interventions to determine how to manage the musculoskeletal side effects of these drugs. Symptoms almost always improve after stopping the drug.

Researchers are trying to determine if switching to a different aromatase inhibitor will prevent the side effects in women who are affected, and they’re testing interventions to manage the side effects. Another option is to switch from an aromatase inhibitor to tamoxifen, which also blocks estrogen but which is not known to cause as much joint and muscle pain.

The findings will be presented on Sept. 8 in San Francisco at the 2007 Breast Cancer Symposium, a scientific meeting sponsored by five leading cancer care societies. (ANI)