Background: The AJCC 7th edition changes the classification of T- and N-factors and the TNM stage of gastric cancer. We evaluated its prognostic impact. Methods: From December 1987 to December 2006, a total of 1,380 patients underwent curative surgery for gastric cancer at the Department of Surgery, Taipei Veterans General Hospital, with a retrieved lymph node number ≥15. Survival was compared for disease classified according to the AJCC 6th and 7th editions. Results: There is a significant difference in 5-year survival between T2 and T3 gastric cancer classified according to the AJCC 7th edition (75.2 vs. 54.9%, p <0.001), as well as between N1 and N2 (71.4 vs. 44.1%, p <0.001). Although patients with N3a had a better 5-year survival than did those with N3b (27.6 vs. 11.3%, p <0.001), the N3 categories were combined and not applied in the TNM stage in the 7th edition. Multivariate analysis using Cox's proportional hazards model with a forward logistics regression stepwise procedure demonstrates that age, N category of 6th edition, and T and N categories of 7th edition are independent prognostic factors; however, T category of 6th edition is no longer significant. Furthermore, the discriminative power of survival difference between each TNM stage seems to be comparable between the 6th and 7th editions. Conclusions: The AJCC 7th edition provides a more stratified survival difference in staging of gastric cancer. Future division of N3a and N3b in the classification of the TNM stage is recommended.
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