Secondly, although our multivariate Cox regression adjusted for key clinical variables (e.g., age, gender, pathologic T/N/M stage, and tumor stage), other unmeasured confounders, such as treatment regimens, comorbidities, or molecular heterogeneity, might influence the prognostic value of PKP2, SMAD9, and GPD1L. This evidence concerns the gene PKP2 and neoplasm.