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The purpose of this study was to clarify the outcome of the ratio between metastatic and examined lymph nodes (N ratio) in gastric cancer patients with ≤15 examined lymph nodes after D2 lymphadenectomy. A retrospective study was performed in 906 patients with gastric cancer who had undergone D2 resection. Patients with ≤15 examined lymph nodes (group 1, n = 729) and those with >15 lymph nodes (group 2, n = 177) were analyzed separately. N ratio categories were identified as follows: N ratio 0, 0%; N ratio 1, 1% to 9%; N ratio 2, 10% to 25%; N ratio 3, >25%. Univariate analysis found that both the tumor, node, metastasis system (N staging system) and N ratio system well classified patients with significantly different prognosis. By multivariate analysis, only the N ratio classification was retained as an independent prognostic factor in both group 1 and 2 compared with the N stage system. Furthermore, when patients were divided into four groups according to the number of lymph nodes examined (1 to 3, 4 to 7, 8 to 11, and 12 to 15), the 5-year survival rates remained similar between groups according to the same N ratio (p > .05). Positive N ratio classification is a better prognostic tool compared with N staging system after D2 resection in patients with gastric cancer. It can prevent stage migration and can be used regardless of the examined number of lymph nodes.

Aim To evaluate the prognostic efficacy of the 7th edition tumor–node–metastasis (TNM) classification compared with the 6th edition in gastric cancer patients. Methods A total of 1,503 gastric cancer patients undergoing surgical resection were staged using the 6th and 7th edition staging systems. Homogeneity, discriminatory ability, and monotonicity of gradients of the two systems were compared using linear trend χ2, likelihood ratio χ2 statistics, and Akaike information criterion (AIC) calculations. Results Significant differences in 5-year survival rates were observed for the T, N, and M subgroups using the 7th edition system, except for stage N2 and N3 patients in the 6th edition system. There were no significant differences in survival between IB and IIA in the 7th edition system. Patients with stage IV disease due to T4/N3 in the 6th edition system who were downstaged to stage III in the 7th edition system had significantly better survival than those who remained at stage IV. The 7th edition system had higher linear trend and likelihood ratio χ2 scores, and smaller AIC values compared with those for the 6th edition, which represented the optimum prognostic stratification. Conclusions Our study suggests that the 7th edition system performs better than the 6th edition in several aspects.