The median PFS ( months ; 95 % CI ) was 2.89 ( 1.94 , 3.38 ) for pemetrexed versus 3.19 ( 2.86 , 4.70 ) for pemetrexed + erlotinib ( hazard ratio [ HR ] 0.63 ; 95 % CI : ( 0.44 , 0.90 ) ; P = 0.0047 ) .