Estimated 12-month survival rates were 74.1 % , 68.4 % , and 58.2 % , respectively ( hazard ratio for death for pembrolizumab every 2 weeks , 0.63 ; 95 % CI , 0.47 to 0.83 ; P = 0.0005 ; hazard ratio for pembrolizumab every 3 weeks , 0.69 ; 95 % CI , 0.52 to 0.90 ; P = 0.0036 ) .