13 percent of women stop taking breast cancer drug because of side effects, U-M s...( ANN ARBOR Mich. More than 10 percen...),Health

ANN ARBOR, Mich. More than 10 percent of women with breast cancer stopped taking a commonly prescribed drug because of joint and muscle pain, according to a new study from researchers at the University of Michigan Comprehensive Cancer Center.

The women in the study were taking aromatase inhibitors, a type of drug designed to block the production of estrogen, which fuels some breast cancers. The treatment is generally given after surgery, chemotherapy or radiation therapy to prevent the cancer from returning. Its typically prescribed as one pill each day for five years. Use of these drugs has increased because they have been shown to be more effective than tamoxifen, the previous standard of care.

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.

Henry will present the findings Sept. 8 in San Francisco at the 2007 Breast Cancer Symposium, a scientific meeting sponsored by five leading cancer care societies.

The study looked at the first 100 women enrolled in a trial to study how genetics play a role in the way individuals metabolize drugs and experience side effects. The women in this analysis were all post-menopausal following treatment for hormone-responsive breast cancer. They 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 qu
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