In addition, univariate Cox regression analysis of PFI revealed that T3 & T4 stage, N2 stage, M1 stage, III & IV pathological stage, lymphatic invasion, perineural invasion, tumor partial response, and complete response after primary therapy, R1 & R2 residual tumor, CEA > 5 ng/mL, and KCNK9 expression were relevant to PFI (Table 4). Here, KCNK9 is linked to neoplasm.