Effect of zoledronic acid on pain associated with bone metastasis in patients with prostate cancer.

Zoledronic acid reduces skeletal-related events associated with prostate cancer and has long-term efficacy in pain outcomes. Findings of treatment group differences in pain early in treatment are less reliable. We used a recently recommended analytic approach to examine the effect of zoledronic acid on pain. In a trial of zoledronic acid (n = 214) versus placebo (n = 208), we used the Brief Pain Inventory to assess pain at baseline, 3 weeks, 6 weeks and every 6 weeks thereafter for a total of 60 weeks. We used a modified longitudinal rank test to determine whether clinically meaningful changes in pain were related to treatment group. Seventy-six of 214 patients (35.5%) receiving zoledronic acid and 62 of 208 patients (29.8%) receiving placebo completed the 60-week visit (P = 0.22). In all 11 pain assessments, patients receiving zoledronic acid reported more favorable, clinically meaningful changes in pain scores. Overall, patients receiving zoledronic acid had a 33% chance of a favorable response, compared with 25% for patients receiving placebo (P = 0.04; 95% CI 0.5% to 15.6%). Zoledronic acid was more likely than placebo to be associated with clinically meaningful reductions in pain. Thus, zoledronic acid may help to avert the pain experienced by patients with progressing metastatic disease secondary to prostate cancer.