Proposal of a novel stage grouping of the Eighth Edition of American Joint Committee on Cancer TNM Staging System for Gastric Cancer: results from a retrospective study of 30 years clinical data from a single institute in China.

: To improve the prognostic accuracy of 8th edition of American Joint Committee on Cancer TNM staging system for gastric cancer by reclassifying N3a category.: 1446 patients who underwent R0 surgery for histologically proven gastric cancers with ≥16 lymph nodes retrieved were selected.: Significant prognostic difference was observed among patients in N3a category ('7-10' group '11-15' group; P = 0.029). We proposed a revised pN category in which patients with '7-10' metastatic lymph nodes were categorized as r-N3a, '11-15' as r-N3b, and '>15' as r-N3c. Prognosis for patients in T2r-N3aM0 was similar to that of patients in T4aN0M0/T3N1M0/T2N2M0/T1r-N3bM0 (P = 0.584), but significantly better than that of patients in T4bN0M0/T4aN1-2M0/T3N2M0/T2r-N3bM0 (P = 0.031). Similarly, prognoses for patients in T3r-N3aM0 and T4ar-N3aM0 were similar to that of patients in T4bN0M0/T4aN1-2M0/T3N2M0/T2r-N3bM0 (P = 0.136; P = 0.193), but significantly better than that of patients in T4bN1-2M0/T4ar-N3bM0/T3r-N3bM0/T1-2r-N3cM0 (P = 0.011; P = 0.017). A revised TNM system was also proposed, in which T2r-N3aM0 was incorporated into stage IIB, T3r-N3aM0 and T4ar-N3aM0 into stage IIIA. The revised TNM system had better homogeneity, discriminatory ability, and monotonicity of gradients than the 8th edition system.: Patients with 7-10 metastatic lymph nodes in T2-T4a categories should be considered lower stage in the final TNM stage.