Median overall survival ( OS ) for WT KRAS mCRC was 23.9 months ( 95 % CI 20.3-27 .7 months ) for arm 1 and 19.7 months ( 95 % CI 17.6-22 .7 months ) for arm 2 ; HR = 0.88 ; 95 % CI 0.73-1 .06 ; P = 0.17 ( 68 % OS events ) .