The median time to first SRE was 31.9 months in the zoledronic acid group ( 95 % CI , 24.2 to 40.3 ) and 29.8 months in the placebo group ( 95 % CI , 25.3 to 37.2 ; hazard ratio , 0.97 ; 95 % CI , 0 to 1.17 ; one-sided stratified log-rank P = .39 ) .