Positive Lymph Node Ratio Is an Independent Prognostic Factor in Gastric Cancer After D2 Resection Regardless of the Examined Number of Lymph Nodes

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.