Background: Phase III trial results showed that denosumab is superior to zoledronic acid (ZA) in preventing skeletal-related events (SREs) in patients with cancer and metastatic bone disease (Lipton et al; 2012, Eur J Cancer). Genitourinary (GU) cancers are some of the most commonly diagnosed cancers worldwide. We now compare the efficacy and safety of denosumab (DMAb) or ZA in a subgroup analysis of patients with GU cancers enrolled in the pivotal phase III trials. Methods: Patients were randomized 1:1 to receive DMAb (120 mg, SC) or ZA (4 mg, IV, adjusted for renal function) every 4 weeks. Daily calcium and vitamin D supplements were strongly recommended. Time to 1st on-study SRE, using a Cox proportional hazards model, time to 1st and subsequent on-study SRE, using the Anderson-Gill model, and safety were evaluated for the GU subgroup in an ad hoc analysis. Results: 2,128 patients (1,052 DMAb; 1,076 ZA) had GU cancers (prostate = 1,901, renal = 155, bladder = 63, and transitional cell = 9). DMAb significantly delayed the time to 1st on-study SRE by 4.0 months compared with ZA (20.7 months vs 16.7 months) in patients with GU cancers (Table). DMAb also significantly delayed the time to 1st and subsequent on-study SRE. Time to disease progression and overall survival were similar between treatment groups. Adverse events (AEs) and serious AEs were reported by similar percentages of patients in both groups (AEs: 96.9% denosumab, 96.8% ZA; serious AEs: 62.8% denosumab, 60.2% ZA). 14.6% of DMAb pts and 15.9% of ZA pts had a renal AE. Hypocalcemia was reported for 12.9% of DMAb patients and 6.2% of ZA patients. There was no significant difference in the incidence of positively adjudicated osteonecrosis of the jaw between the DMAb (2.2%) and ZA (1.6%) groups (p=0.34). Conclusions: Among patients with GU cancers and metastatic bone disease, DMAb was superior to ZA in preventing SREs. Clinical trial information: NCT00330759 and NCT00321620.

* Multiple-event analysis; reported as a rate ratio.