At a median follow-up of 49.2 months ( IQR 47.0-51 .8 ) , 741 ( 96 % ) of the prespecified 773 death events for the final analysis had been observed : 354 ( 65 % ) of 546 patients in the abiraterone acetate group and 387 ( 71 % ) of 542 in the placebo group .