The estimated 6-month progression-free-survival rates were 47.3 % for pembrolizumab every 2 weeks , 46.4 % for pembrolizumab every 3 weeks , and 26.5 % for ipilimumab ( hazard ratio for disease progression , 0.58 ; P < 0.001 for both pembrolizumab regimens versus ipilimumab ; 95 % confidence intervals [ CIs ] , 0.46 to 0.72 and 0.47 to 0.72 , respectively ) .