Zoledronic Acid for Treatment of Osteopenia and Osteoporosis in Women with Primary Breast Cancer (BC) Undergoing Adjuvant Aromatase Inhibitor (AI) Therapy.

Abstract

Abstract Background: Postmenopausal women with significant osteopenia/osteoporosis are at increased risk of fracture, a risk that is exacerbated by the use of Aromatase Inhibitors (AIs). Bisphosphonates may be used for these patients because there is no known interaction with estrogen and/or progesterone receptors (ER, PR). This study evaluated the concurrent use of zoledronic acid in patients with significant osteopenia or osteoporosis who received initial adjuvant letrozole therapy for primary BC, to determine if further bone mineral density (BMD) loss could be prevented.Methods: Postmenopausal women with Stage I-IIIa, ER and/or PR + BC, no evidence of metastatic disease, and a BMD T-score < -2.0 were treated with daily letrozole 2.5 mg/d, vitamin D 400 international units/d, calcium 500 mg twice daily, and 4 mg I.V. zoledronic acid every 6 months (for 5 years). The BMD was measured at baseline and at one year. Kruskall-Wallis p-value methodology was used as the method of statistical analysis. Since this was a single-arm study, the analysis plan was primarily descriptive. The primary endpoint was the mean change in lumbar spine (LS) BMD at 1 year.Results: 60 patients were enrolled; 46 completed 1 year of treatment. Mean patient age was 67 years, with 44% having taken prior tamoxifen. At 1 year (see figure 1), LS BMD increased 2.66% (p=0.01), femoral neck (FN) BMD increased 4.81% (p=0.01), and any measured endpoint (within the LS or FN) increased 4.55% (p=0.0052). 7% of patients experienced a fracture vs.13% with a pre-existing history of fracture before enrollment. No patients had disease recurrence during year 1. Toxicity was minimal with arthralgia as the most common complaint. There were no reports of osteonecrosis of the jaw.Conclusion: Zoledronic acid prevents additional bone loss in postmenopausal women with significant osteopenia or osteoporosis initiating letrozole. Treatment with zoledronic acid was associated with an improvement in BMD. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2103.