(HealthDay News) — In the long-term, adjuvant zoledronic acid 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 annual San Antonio Breast Cancer Symposium, held from Dec. 6 to 10.
Michael Gnant, MD, from 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 (hazard ratio [HR], 0.73) and death (HR, 0.59).
Richard de Boer, MD, from the Royal Melbourne Hospital in Australia, and colleagues compared the benefit of immediate zoledronic acid or delayed zoledronic acid 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 versus delayed zoledronic acid (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 was associated with significantly improved DFS and prolonged overall survival versus delayed zoledronic acid (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 ZOL (4mg every 6 months) to adjuvant letrozole therapy for early breast cancer,” de Boer and colleagues write.