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In a study of premenopausal women with early-stage breast cancer treated with a combination of hormonal therapies, use of the bisphosphonate drug Zometa® (zoledronic acid) prevented bone loss. These results were published in the Journal of Clinical Oncology.

Each year breast cancer is diagnosed in over 200,000 women in the U.S. alone. Many of these breast cancers will be hormone receptor-positive, meaning that they are stimulated to grow by the circulating female hormones estrogen and/or progesterone.

The growth of estrogen receptor-positive breast cancer cells can be prevented or slowed by reducing the exposure to estrogen. Tamoxifen reduces estrogen exposure by blocking hormone receptors. Drugs known as aromatase inhibitors reduce estrogen exposure by inhibiting the production of estrogen in tissues outside of the ovaries.

In premenopausal women, who have high levels of estrogen produced by the ovaries, suppression of ovarian hormone production is another approach to reducing estrogen exposure. Drugs known as leuteinizing hormone releasing hormone (LHRH) agonists, such as Zoladex® (goserelin), suppress hormone production by the ovaries.

A common side effect of some hormonal therapies is loss of bone density. Drugs known as bisphosphonates may be able to prevent this bone loss.

To assess the effect of the bisphosphonate drug Zometa® (zoledronic acid) in premenopausal breast cancer patients, researchers in Austria evaluated information from a clinical trial of two different approaches to hormonal therapy.

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The trial enrolled premenopausal women with Stage I or Stage II, estrogen receptor-positive and/or progesterone receptor-positive breast cancer. Women were treated with either Zoladex plus tamoxifen or Zoladex plus the aromatase inhibitor Arimidex® (anastrozole). In addition, half the women received treatment with Zometa.

  • Women who did not receive Zometa during hormonal therapy experienced significant loss of bone mineral density. Bone loss was worse for women treated with Zoladex and Arimidex than for women treated with Zoladex and tamoxifen.
  • In women who did receive Zometa during hormonal therapy, bone mineral density remained stable.

The researchers conclude that Zometa prevented bone loss in premenopausal women receiving a combination of hormonal therapies. The researchers note that regular bone mineral density measurements, with use of a bisphosphonate drug if bone loss is identified, should be considered for patients at risk of bone loss due to hormonal therapy.

Reference: Gnant MFX, Mlineritsch B, Luschin-Ebengreuth G et al. Zoledronic Acid Effectively Prevents Cancer Treatment-induced Bone Loss in Premenopausal Women Receiving Adjuvant Endocrine Therapy for Hormone-responsive Breast Cancer: A Report from the Austrian Breast and Colorectal Cancer Study Group. Journal of Clinical Oncology. Early online publication December 11, 2006.

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