The Comparison between 6th and 7th UICC/AJCC N Stage for Prognostic Significance in Gastric Cancer

Purpose: The 7th edition UICC/AJCC TNM classification for gastric cancer has several changes from the previous edition. Especially, the classification of the number of lymph node metastases (LNM) is reorganized. According to the new TNM system, N stage was categorized to N0 (no LNM), N1 (1∼2 LNM), N2 (3∼6 LNM), N3 (7 or more LNM). The aim of our study was to compare the prognostic significance of the new (7th) UICC/AJCC N stage with the old (6th). Methods: From 2000 to 2005 a total of 425 patients who underwent curative resections with D2 and with 15 or more lymph nodes retrieved were studied retrospectively. Results: According to the 7th UICC/AJCC N stage, the 5-year cumulative survival rates (5YSR) of N0, N1, N2, N3 were 96.0%, 79.2%, 58.5% and 24.3%, respectively (P0.001). Using univariate analysis, the N stage of 7th and 6th UICC/AJCC TNM classification, 7th UICC/AJCC T stage, differentiation of tumor, type of gastrectomy (subtotal and total gastrectomy), size of primary tumor (≤5, 5≤10, 10) were associated with 5YSR. However, Cox regression multivariate analysis showed the 7th UICC/AJCC N stage to bean independent factor for predicting the 5YSR instead of the 6th UICC/AJCC N stage (P0.001, hazard ratio (HR) 1.859, 95% confidence interval (CI) 1.576∼2.194), including depth of tumor invasion (P0.001, HR 1.673, 95% CI 1.351∼2.073). Conclusion: The new (7th) UICC/AJCC N stage is a more reliable prognostic factor of gastric cancer than the old (6th) N stage.