The benefits of timely intervention with zoledronic acid in patients with metastatic prostate cancer to bones: a retrospective study of the US Veterans Affairs population.

To examine the effect of timely zoledronic acid (ZA) treatment on clinical outcomes and health care utilization in patients with bone-metastatic prostate cancer. Patients with prostate cancer and bone metastasis were identified in a Veterans Affairs database (01/2002-09/2009). Eligible patients had no documented skeletal-related events (SREs) before the index date (that is, the first bone metastasis diagnosis date). Patients who received early ZA treatment, defined as having a ZA infusion after the index date and before any recorded SREs, were matched 1:1 on propensity score to patients not treated with bisphosphonates (BPs). Risks of SREs, hospitalization and death during the 6-month post-index period were compared between matched cohorts using Kaplan-Meier analyses. Baseline characteristics were well balanced between the matched cohorts (n = 73 per group). 6-month SRE-free survival and hospitalization-free survival were higher in patients receiving timely ZA than patients without BP treatment (91.7 versus 71.5%, P < 0.01; 80.5 versus 66.3%, P = 0.05, respectively). 6-month mortality risk was significantly lower in patients treated with ZA versus those without BP treatment (4.3 versus 13.8%, P = 0.04). Timely ZA intervention in bone-metastatic prostate cancer patients was associated with significant reductions in 6-month risks of SREs, hospitalization and mortality, as compared with no BP treatment.