OS was significantly improved with enzalutamide over placebo in patients < 75 years [ median not yet reached versus 13.6 months ; HR 0.63 ( 95 % CI 0.52-0 .78 ) , P < 0.001 ] and in patients 75 years [ median 18.2 versus 13.3 months ; HR 0.61 ( 95 % CI 0.43-0 .86 ) , P = 0.004 ] , respectively .