Osteonecrosis of the jaw (ONJ) was seen infrequently in both treatment groups (20 patients receiving denosumab (2.0 percent) as compared with 14 patients (1.4 percent) receiving Zometa). There was no statistically significant difference in the rate of ONJ between the two treatment arms. Hypocalcemia occurred more frequently with denosumab. No AEs of hypocalcemia were reported as fatal, and grade 3 or 4 AEs of hypocalcemia were similar between groups (1.6 percent denosumab, 1.2 percent zoledronic acid). Overall survival (hazard ratio 0.95, 95 percent CI: 0.81, 1.11; p=0.50) and time to cancer progression (hazard ratio 0.99, 95 percent CI: 0.89, 1.11; p=0.90) was balanced between treatment arms.

Study Design This study was an international, randomized, double-blind, double-dummy, active-controlled study, in which breast cancer patients were randomized to receive either subcutaneous denosumab 120 mg and intravenous placebo (N=1,026), or Zometa administered intravenously as at least a 15 minute infusion at a dose of 4 mg (or equivalent creatinine clearance-adjusted dose in patients with baseline creatinine clearance < 60 mL/min) every four weeks as per the labeled instructions. All patients were strongly recommended to take daily calcium and vitamin D supplements.  The primary endpoint was time to first on-study SRE.