A total of 626 patients ( 72 % ) in the enzalutamide group , as compared with 532 patients ( 63 % ) in the placebo group , were alive at the data-cutoff date ( 29 % reduction in the risk of death ; hazard ratio , 0.71 ; 95 % CI , 0.60 to 0.84 ; P < 0.001 ) .