Prognostic Discrepancy of the 6th and 7th UICC N Classification for Lymph Node Staging in Gastric Cancer Patients after Curative Resection

BACKGROUND The validity of N classification of the 7th edition of the American Joint Committee on Cancer/Union Internationale contre le Cancer (AJCC/UICC) tumor-node-metastasis (TNM) staging system is still under debate. The purpose of this study was to evaluate the prognostic efficacy of the 7th edition of the AJCC/UICC TNM staging system (focusing on N stage), in comparison with the 6th edition, at a single Eastern institution. METHODS We analyzed 1,435 patients with gastric cancer who underwent curative resection performed from September 1998 to August 2003 at the Memorial Jin-Pok Kim Korea Gastric Cancer Center. We analyzed the survival rate of the patients according to the AJCC/UICC 6th and 7th editions, and compared each stage, focusing on N stage. RESULTS Significant differences in the 5-year survival rates were observed between the 6th and the 7th AJCC/UICC staging system. In the 6th edition staging system, the Kaplan-Meier curves discriminated each N stage significantly. In contrast, there was no difference in terms of survival curves for N stage according to the 7th edition, especially between N1 and N2: the Kaplan-Meier plots of survival curves between N1 (77.0%) and N2 (78.1%) stages overlapped significantly (p < 0.05). CONCLUSION Although the 7th UICC staging system is a more detailed and sophisticated system in the T category, there was no prognostic significance between the pN1 and pN2 stages according to our data. Therefore, we suggest establishing a new UICC staging system taking into consideration the application of the N stage.