Comparative study of the 7(th) and 8(th) AJCC editions for gastric cancer patients after curative surgery

OBJECTIVES: The classification of pathological tumor-node-metastasis (pTNM) staging of gastric cancer was revised in the 8(th) American Joint Committee on Cancer (AJCC) edition. The major revision was the separation of pN3a and pN3b in the pTNM staging. The current study evaluated the prognostic impact of this change. METHODS: A total of 1,517 patients who underwent curative surgery for gastric cancer with a retrieved lymph node number ≥15 at our institution from January 1995 to December 2011 were enrolled. Survival was compared for the disease classified according to both the 7(th) and 8(th) editions. RESULTS: After separation of pN3a and pN3b in the pTNM stage definition, the 8(th) edition still provides significant survival differences between each stage. The multivariate analysis demonstrated that the pTNM stage in both the 7(th) and 8(th) editions was an independent prognostic factors of overall survival and disease-free survival. The 8(th) edition has a better homogeneity than the 7(th) edition with a significantly higher likelihood ratio chi-square test. Regarding the OS and DFS, the time-dependent receiver operating characteristic (ROC) curves of the two staging systems are almost overlapping, indicating that the prognostic performance is comparable between the two staging systems. CONCLUSIONS: Both the 7(th) and 8(th) edition-based stages are independent prognostic factors for gastric cancer. The 8(th) edition has a better homogeneity than the 7(th) edition; the 8(th) edition provides discriminant survival differences among each pTNM stage that are comparable to those in the 7(th) edition.