Comparison of the staging of regional lymph nodes using the sixth and seventh editions of the tumor-node-metastasis (TNM) classification system for the evaluation of overall survival in gastric cancer patients: Findings of a case-control analysis involvin

BackgroundIt has recently been reported that the sixth edition of the tumor-node-metastasis (TNM) classification system for gastric cancer involving the staging of regional lymph nodes (N) has inappropriate cut-offs with regard to counts of metastatic lymph nodes. It remains controversial, however, as to whether the seventh edition of this classification system is completely accurate in staging N for the prediction of the prognosis of gastric cancer. Our aim was to determine which of these two editions of the TNM classification system was superior with regard to the prediction of the prognosis of Chinese patients with gastric cancer.MethodsWe analyzed relevant clinicopathological data statistically from 1,563 patients with gastric cancer who had undergone curative resection to evaluate the sixth and seventh editions of the TNM classification system for N staging with regard to the prediction of overall survival (OS).ResultsOur survival analyses demonstrated that N staging via use of both the sixth and seventh editions of the TNM classification system was correlated with OS. Furthermore, case-control analysis indicated that the seventh edition was significantly superior to the sixth edition in predicting the OS of patients, regardless of the extent of lymphadenectomy (D1 or D2) and the number of dissected lymph nodes (<16 or ≥16). By taking into consideration both the extent of lymphadenectomy and the number of dissected lymph nodes simultaneously, we determined that the seventh edition of the TNM classification system was superior to the sixth edition regarding the evaluation of the OS in the various subgroups of gastric cancer patients.ConclusionThe seventh edition proved more reliable and accurate than the sixth edition of the TNM classification system in categorizing the number of metastatic lymph nodes for the purpose of predicting the OS of patients with gastric cancer after curative resection.