Evaluation of the seventh edition of American Joint Committee on Cancer TNM staging system for gastric cancer: results from a Chinese monoinstitutional study.

BACKGROUND: To investigate the validity of the 7th edition of American Joint Committee on Cancer (AJCC) TNM staging system for gastric cancer with special attention paid to pT2/pT3, pN1/pN2, and pN3a/pN3b category.
MATERIALS AND METHODS: Clinicopathologic data of 1998 patients underwent R0 surgery for histologically proven gastric cancers with >15 lymph nodes retrieved were retrospectively reviewed.
RESULTS: Prognoses were significantly different between pT2 and pT3 categories, between pN1 and pN2 categories, or between pN3a and pN3b categories. Each stage in the 6th edition was divided into the 7th edition stage with different survival rates. Moreover, stage IIIA, IIIB, and IIIC in the 7th edition system was divided into the 6th edition stage with different survival rates. Prognoses for patients in 7th edition T4aN1M0/T3N2M0/T2N3aM0, T4bN0-1M0/T4aN2M0/T3N3aM0, and T4aN3aM0/T4bN2M0 were similar to that of patients in T1N3bM0, T2N3bM0, and T3N3bM0, respectively, but significantly better than that of patients in T2N3bM0, T3N3bM0, and T4aN3bM0, respectively. However, no significant difference could be observed among patients in T4bN3aM0, T4aN3bM0, T4bN3bM0, and stage IV. A revised TNM system was proposed, in which T1N3bM0 was incorporated into stage IIIA, T2N3bM0 into stage IIIB, T3N3bM0 into stage IIIC, T4bN3aM0/T4aN3bM0/T4bN3bM0 into stage IV. Further analyses revealed the revised TNM system had better homogeneity, discriminatory ability, and monotonicity of gradients than the 6th and the 7th edition system.
CONCLUSIONS: It is reasonable to subclassify the 6th edition pT2 category and pN1 category into the 7th edition pT2/pT3 category and pN1/pN2 category, respectively. However, for better prognostic stratification, it might be more suitable for pN3a and pN3b categories to be considered individual determinants of the 7th edition TNM staging system.