Superiority of denosumab to zoledronic acid for prevention of skeletal-related events : a combined analysis of 3 pivotal, randomised, phase 3 trials

Background: Patients with bone metastases from advanced cancer often experience skeletal-related events (SRE), which cause substantial pain and morbidity. Denosumab, a fully human monoclonal antibody that inhibits RANK Ligand (RANKL), is a novel bone-targeted agent with a distinct mechanism of action relative to the bisphosphonate zoledronic acid, for prevention of SRE. This pre-planned analysis evaluates the efficacy and safety of denosumab versus zoledronic acid across three pivotal studies. Methods: Patient-level data from three identically designed, randomised, double-blind, active-controlled, phase 3 trials of patients with breast cancer, prostate cancer, other solid tumours or multiple myeloma were combined. End-points included time to first SRE, time to first and subsequent (multiple) SRE, adverse events, time to disease progression and overall survival. Findings: Denosumab was superior to zoledronic acid in delaying time to first on-study SRE by a median 8.21 months, reducing the risk of a first SRE by 17% (hazard ratio, 0.83 [95% confidence interval (CI): 0.76-0.90]; P < 0.001). Efficacy was demonstrated for first and multiple events and across patient subgroups (prior SRE status; age). Disease progression and overall survival were similar between the treatments. In contrast to zoledronic acid, denosumab did not require monitoring or dose modification/withholding based on renal status, and was not associated with acute-phase reactions. Hypocalcaemia was more common for denosumab. Osteonecrosis of the jaw occurred at a similar rate (P = 0.13). Conclusion: Denosumab was superior to zoledronic acid in preventing SRE with favourable safety and convenience in patients with bone metastases from advanced cancer.