943 PAIN INTERFERENCE WITH DAILY FUNCTIONING IN PATIENTS WITH CASTRATE-RESISTANT PROSTATE CANCER: A COMPARISON OF DENOSUMAB AND ZOLEDRONIC ACID

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INTRODUCTION AND OBJECTIVES: Men with castrate-resistant prostate cancer (CRPC) who develop bone metastases may experience pain that seriously impacts function and quality of life. A recent randomized phase 3 trial demonstrated superiority of denosumab to zoledronic acid (ZA) for prevention of skeletal complications of bone metastases in men with CRPC. Here we report the results of pain interference (PI) with daily functioning. METHODS: Patients with CRPC and 1 site of bone metastasis received either subcutaneous (SC) denosumab 120 mg and intravenous (IV) placebo (n 950) or IV ZA 4 mg and SC placebo (n 951) every 4 weeks. PI with daily functioning (overall; activity [general activity, walking, work]; and affect [mood, enjoyment of life, relations with others]) was assessed using the Brief Pain Inventory at baseline and before each monthly visit. Responses on a scale of 0 (no) to 10 (complete) interference were analyzed for all randomized patients through month 18, when 50% of patients had dropped out due to death, disease progression, or consent withdrawal. RESULTS: Overall, from month 1 to 18, the average relative proportion of patients who reported increased PI ( 2 point increase) was 5% greater in the ZA group than in the denosumab group. Among patients with no/mild pain at baseline (56%), 13% more in the ZA group had increased PI relative to denosumab. For PI activity and affect domains, overall relative proportional differences between ZA and denosumab were 6% and 5%, respectively, favoring denosumab. For patients with no/mild pain at baseline, the average relative proportional differences for both domains were 13% each (Figure: Activity). CONCLUSIONS: In this trial of men with CRPC and bone metastases, denosumab was associated with a reduced incidence of increased pain interference over the study period compared with ZA, and this was further accentuated in patients with no or mild pain at baseline. Effective management of the impact of pain on patients’ daily lives is important to minimize patients’ distress and maintain quality of life. Preservation of physical function and mood, particularly in the early stages of treatment, contributes substantially towards this goal.