Zoledronate plus hormone therapy for premenopausal breast cancer reduces relapse

NEW YORK (Reuters Health) - In premenopausal women with endocrine-responsive early breast cancer, addition of the bisphosphonate zoledronic acid to endocrine therapy significantly improves disease-free survival, physicians in Europe report in the New England Journal of Medicine for February 12.

Lead author Dr. Michael Gnant at the Medical University of Vienna, Austria, and his associates note that in an earlier study in premenopausal women with advanced breast cancer, ovarian suppression with gonadotropin-releasing hormone analogues in combination with an aromatase inhibitor reduced circulating estrogen levels more effectively than ovarian suppression plus tamoxifen.

They point out further that the anti-osteoporosis drug zoledronate prevents bone loss associated with aromatase inhibitors in breast cancer patients and may also possess antitumor and antimetastatic properties.

In the Austrian Breast and Colorectal Cancer Study Group trial 12 (ABCSG-12), 1803 patents were treated with the gonadotropin-releasing hormone analogue goserelin (3.6 mg by subcutaneous injection every 28 days). They were randomly assigned in a 1:1:1:1 ratio to treatment with tamoxifen (20 mg/d) or anastrozole (1 mg/d), with or without zoledronic acid (4 mg IV every 6 months). Treatment duration was 3 years.

After a median follow-up of 47.8 months, disease-free survival was 90.8% in patients treated with endocrine therapy alone vs 94.0% in patients who received endocrine therapy plus zoledronic acid (p = 0.01), representing a 36% reduction in the risk of disease progression. Survival rates were similar in the two groups: 97.1% vs 98.2%.

Clinical outcomes were similar for tamoxifen and anastrozole, with disease-free survival rates of 92.8% and 92.0%, respectively. The authors report that "adverse events were consistent with known drug-safety profiles," and there were no treatment-related deaths.

"These outcomes add to the growing body of data showing that subgroups of patients with low-risk or intermediate-risk, endocrine-responsive early breast cancer can be spared the adverse events of cytotoxic therapy after locoregional treatment," Dr. Gnant and associates conclude.

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