(HealthDay News) – In the long-term, adjuvant zoledronic acid (ZOL) is associated with a significant reduction in disease-free survival (DFS) events and death in premenopausal women with endocrine-receptor positive early-stage breast cancer; and for postmenopausal women with hormone receptor-positive early breast cancer, immediate treatment with zoledronic acid is associated with a reduced risk of DFS events, according to two studies presented at the 2011 San Antonio Breast Cancer Symposium.
Michael Gnant, MD (of the Medical University of Vienna in Austria) and colleagues investigated the long-term effect of adjuvant zoledronic acid for premenopausal patients with endocrine-responsive early stage breast cancer. At a median follow-up of 76 months, compared with patients not receiving zoledronic acid, those patients receiving zoledronic acid treatment had a significant reduction in the risk of DFS events (HR, 0.73) and death (HR, 0.59).
Richard de Boer, MD (of the Royal Melbourne Hospital in Australia) and colleagues compared the benefit of immediate (IMZOL) or delayed (DZOL) treatment with zoledronic acid, for 1,065 postmenopausal women with hormone receptor-positive early breast cancer. At 60 months of follow-up, there was a significant reduction in the risk of a DFS event with immediate zoledronic acid treatment versus delayed zoledronic acid treatment (HR, 0.66). For women who were postmenopausal for more than five years, or were older than 60 at the study entry, immediate zoledronic acid treatment was associated with significantly improved DFS and prolonged overall survival versus delayed zoledronic acid treatment (HR, 0.63 and 0.50, respectively).
“Long-term follow-up in [the] Zometa-Femara Adjuvant Synergy Trial confirms the overall survival benefits of adding zoledronic acid (4mg q6mo) to adjuvant letrozole therapy for early breast cancer,” de Boer and colleagues write.