Lymph node ratio is an independent prognostic factor in gastric cancer after curative resection (R0) regardless of the examined number of lymph nodes.

Objectives: The purpose of this study was to evaluate the outcome of the ratio between metastatic and examined lymph nodes (N ratio) in gastric cancer patients with < 15 examined lymph nodes after curative resection. Methods: A retrospective study of 710 patients who underwent radical gastrectomy (R0) for gastric cancer from January 1980 to December 2000 was analyzed statistically to identify the N ratio. Patients with < 15 examined lymph nodes (group 1, n = 327) and those with >= 15 examined lymph nodes (group 2, n = 383) 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%; and N ratio 3, > 25%. All the enrolled categories were evaluated by the best cutoff approach. Results: The univariate analysis showed that age, tumor site, tumor size, surgery, T categories, number of metastatic nodes, and N ratio significantly affected prognosis in groups 1 and 2. By multivariate analysis, the N ratio (but not the TNM N category) classification was retained as an independent prognostic factor in groups 1 and 2 compared with the N category system. However, patients with N1 disease in group 1 obtained a better postoperative prognosis than those with N1 disease in group 2 according to the N stage classification (P = 0.003). When the N ratio classification was applied, no significant differences were found for N ratios 0, 1, 2, or 3 between the 2 groups (P > 0.05). Conclusions: The metastatic lymph node ratio is an independent prognostic factor regardless of the examined number of lymph nodes. In predicting the prognosis of gastric cancer, the staging system based on the metastatic lymph node ratio is more reliable than the system based on the number of metastatic lymph nodes regardless of the examined number of lymph nodes. This can help improve the TNM staging classification of gastric cancer and reduce the International Union Against Cancer N categories of stage migration.