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Breast Cancer Health Center

FDA Approves New Use for Breast Cancer Drug

Aromasin May Now Treat Early Breast Cancer in Postmenopausal Women
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FDA's Decision

According to a Pfizer news release, the FDA approved Aromasin's new use based on a study of more than 4,700 postmenopausal women with estrogen receptor-positive breast cancer.

That study was published in The New England Journal of Medicine in March 2004.

All of the women had taken tamoxifen for two to three years. About half were then switched to Aromasin; others kept taking tamoxifen. Each woman got a combined total of five years of drug therapy. They didn't know which drug they were taking.

Those who were switched to Aromasin had 32% more protection from cancer's return.

"[Aromasin] therapy after two to three years of tamoxifen therapy significantly improved disease-free survival as compared with the standard five years of tamoxifen treatment," the researchers wrote.

Severe side effects were rare in their study.

Aromatase Inhibitors

Aromasin is part of a newer family of breast cancer drugs called aromatase inhibitors. Those drugs also include Femara and Arimidex.

Arimidex was recently compared to tamoxifen in a similar Austrian study. The results, published in The Lancet in August, showed fewer cancer recurrences in women who were switched to Aromasin after taking tamoxifen for about two years, instead of continuing with tamoxifen.

Femara also beat tamoxifen in yet another study, which was presented in May at the annual meeting of the American Society of Clinical Oncology.

None of those studies did a head-to-head comparison of aromatase inhibitors.

Aromatase inhibitors are generally known for a lower risk of blood clots compared with tamoxifen, yet they appear to have a higher risk of bone loss and fracture. As relatively new drugs, there is still more to learn about them. Aromatase inhibitors are also more costly than tamoxifen, which is now available as a generic drug.

Different From Tamoxifen

Like tamoxifen, aromatase inhibitors target estrogen, which fuels some (but not all) breast cancers.

Tamoxifen blocks estrogen receptors on cells. It acts like your car's gas cap, preventing the "fuel" (estrogen) from getting into the "tank" (the cell).

Aromatase inhibitors work differently. They curb estrogen production. That way, there's no "gas" to go in the "tank."

Tamoxifen has been a major part of breast cancer treatment for more than 20 years. It's typically taken for five years after surgery, chemotherapy, and radiation to try to prevent cancer's return.

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