• R Coleman, R de Boer, H Eidtmann, A Llombart, N Davidson, P Neven, G von Minckwitz, H P Sleeboom, J Forbes, C Barrios, A Frassoldati, I Campbell, O Paija, N Martin, A Modi, and N Bundred.
• Academic Unit of Clinical Oncology, CR-UK/YCR Sheffield Cancer Research Centre, Sheffield, UK. Electronic address: r.e.coleman@sheffield.ac.uk.
• Ann. Oncol. 2013 Feb 1; 24 (2): 398-405.

BackgroundAromatase inhibitors are the preferred adjuvant endocrine therapy for the majority of postmenopausal women with hormone-responsive early breast cancer. Although generally more effective than tamoxifen, aromatase inhibitor therapy is associated with increased bone loss and fracture risk.Patients And MethodsPostmenopausal women receiving adjuvant letrozole (2.5 mg/day for 5 years; N = 1065) were randomly assigned to immediate zoledronic acid (zoledronate) 4 mg every 6 months for 5 years, or delayed zoledronate (initiated for fracture or on-study bone mineral density [BMD] decrease). The primary end point was the change in lumbar spine BMD at 12 months. Lumbar spine and total hip BMD at subsequent follow-up, disease-free survival (DFS), and overall survival were assessed as secondary end points.ResultsAt 60 months (final analysis), the mean change in lumbar spine BMD was +4.3% with immediate zoledronate and -5.4% with delayed intervention (P < 0.0001). Immediate zoledronate reduced the risk of DFS events by 34% (hazard ratio [HR] = 0.66; P = 0.0375) with fewer local (0.9% versus 2.3%) and distant (5.5% versus 7.7%) recurrences versus delayed zoledronate. In the delayed group, delayed initiation of zoledronate substantially improved DFS versus no zoledronate (HR = 0.46; P = 0.0334).ConclusionsImmediate zoledronate in postmenopausal women receiving letrozole preserved BMD and is associated with improved DFS compared with letrozole alone. Clinical Trials Registration No NCT00171340.

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