(ChemotherapyAdvisor) – Exploratory analysis of a Phase 3 trial that concluded denosumab prolonged bone metastasis-free survival in men with nonmetastatic castrate-resistant prostate cancer (CRPC) at high risk of such metastasis has found the agent’s benefits are greatest in those with very rapid prostate specific antigen (PSA) kinetics, according to a study presented at the 2012 Genitourinary Cancers Symposium.

Matthew R. Smith, MD, PhD, of the Massachusetts General Hospital Cancer Center and colleagues evaluated bone metastasis-free survival in a subset of 1,432 men with nonmetastatic CRPC enrolled in the Phase 3 trial who had a baseline PSA doubling time of <6 months. Patients were randomized to receive subcutaneous denosumab 120mg or placebo.

In this analysis, men in the denosumab group (n=419) had bone metastasis-free survival prolonged by a median of 7.2 months, with a 23% reduction in risk vs. placebo (P=0.0064). The placebo group (n=427) had a PSA doubling time that was 6.5 months shorter than the overall population, 18.7 vs. 25.2 months, suggesting this population of men is at particularly high risk, the investigators noted.

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Denosumab (XGEVA), manufactured by Amgen, is currently approved for use in metastatic disease only.

The 2012 Genitourinary Cancers Symposium is sponsored by the American Society of Clinical Oncology, American Society for Radiation Oncology, and the Society of Urologic Oncology.