Abstract: Objective：To observe the treatment effect of zoledronic acid dosing every 12 VS 4 weeks in patients with prostate cancer metastatic to bone.Methods:52 patients with prostate cancer and bone metastases were assigned to receive 4.0mg of intravenous zoledronic acid every 4 （group A）or every 12 weeks （group B）for 1 year.The clinical value about twoway therapy were evaluated on SRE rate、first SRE and skeletal morbidity rate、uNTX/Cr ratio、bone pain relief rate、number of bone metastases and adverse events.Results：Treatment delay was observed in 64.0% of group A and 33.3% of group B，and the difference between the two groups was statistically significant（P<0.05）.SREs occurred in 5 patients（20.0%）in group A and 6 patients（22.2%）in group B.The SREs rate and the time to first SRE（occured about 30 weeks）between two groups were not significantly different（P＞0.05）.The mean SMR was 0.46 vs 0.50 events per year in in group A and group B（P＞0.05）.The uNTX/Cr ratio had no statistical difference between the 2 treatment groups in each time period（P＞0.05），except at the 48 weeks.Bone pain relief rate of two groups was not statistically significant in each time point.Adverse events：In group A，the proportion of patients in digestive tract reaction and hypopotassemia was higher than another group.But all AEs in two groups had no statistical difference.Conclusion：The every 12 weeks regimen of zoledronic acid was noninferior to the every 4 weeks regimen for treatment of patients with bone metastasis from prostate cancer in relief bone pain and control the progression of bone lesions.This longer interval may be an acceptable treatment option.

Key words: zoledronic acid, bone metastases, prostate cancer