KRAS mutations in codon 12 ( multivariate HR , 1.52 ; 95 % confidence interval , CI , 1.28-1 .80 ; P < 0.0001 ) or codon 13 ( multivariate HR , 1.36 ; 95 % CI , 1.04-1 .77 ; P = 0.0248 ) were significantly associated with shorter DFS compared with patients with wild-type KRAS/BRAF tumors , independent of covariates .