August 19 (HealthDay News) -- Zoledronic acid prevents bone loss in breast cancer patients undergoing endocrine therapy and improves bone mineral density after treatment, according to an Austrian study.

Adjuvant endocrine therapy is widely used in patients with endocrine-responsive early breast cancer, but the treatment causes bone loss in premenopausal women.

This study by Michael Gnant of the Medical University of Vienna, General Hospital Vienna, and colleagues included 404 premenopausal breast cancer patients randomly assigned to receive three years of either goserelin plus tamoxifen with or without zoledronic acid or goserelin plus anastrozole with or without zoledronic acid.

The women's bone mineral density was measured at the start of the study and again at six, 12, 36 and 60 months.

After three years of treatment, the women who received endocrine therapy alone (199) showed significant loss of bone mineral density (BMD). Partial recovery of BMD was noted at five years (two years after completion of endocrine therapy), but their BMD was still lower than it was at the start of the study.

BMD among the women who received zoledronic acid (Zometa) while undergoing endocrine therapy (205) remained stable at three years and increased at five years.

The study was published online and was expected to be in the September print issue of The Lancet Oncology.

"The findings presented here offer important information related to bone health for premenopausal women undergoing adjuvant endocrine therapy," Gnant wrote.

SOURCE: The Lancet, news release, Aug. 20, 2008