KRAS and neoplasm: There were no significant differences in mean ages, gender, tumor location, histological type, tumor depth, lymph node metastasis, retrieved lymph node number, vascular invasion, perineural invasion, pre-operative serum CEA level, and post-operative serum CEA level between patients with wild-type KRAS and those with mutated KRAS. Moreover, OS (23.04 vs. 18.74 months, P = 0.074) and PFS (10.22 vs. 7.95 months, P = 0.101) were also not significantly different.