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. The gene discussed is SMAD9; the disease is neoplasm.