Lymph-node ratio is an important clinical determinant for selecting the appropriate adjuvant chemotherapy regimen for curative D2-resected gastric cancer.

Purpose: Adjuvant chemotherapy for gastric cancer, particularly stage III, improves survival after curative D2 gastrectomy. We investigated the clinical value of the lymph-node ratio (LNR; number of metastatic lymph nodes/number of lymph nodes examined) for selecting the appropriate adjuvant chemotherapy regimen in patients with D2-resected stage II/III gastric cancer.

Methods: We reviewed the data of 819 patients who underwent curative D2 gastrectomy followed by adjuvant chemotherapy. Of them, 353 patients received platinum-based chemotherapy and 466 received TS-1. The patients were categorized into three groups according to their LNR (LNR 1, 0-0.1; LNR 2, > 0.1-0.25; and LNR 3, > 0.25), and their disease-free survival (DFS) was evaluated.

Results: The DFS curves of the patients were well separated according to stage and LNR. In multivariate analyses, an LNR > 0.1 was strongly associated with the 3-year DFS (hazard ratio 2.402, 95% confidence interval 1.607-3.590, P < 0.001). Platinum-based chemotherapy improved the 3-year DFS compared to TS-1 in patients with LNR 3 group in stage III gastric cancer (platinum vs. TS-1, median DFS 26.87 vs. 16.27 months, P = 0.028). An LNR > 0.1 was associated with benefiting from platinum-based adjuvant chemotherapy in stage III gastric cancer patients with lymphovascular invasion (platinum vs. TS-1, median DFS 47.57 vs. 21.77 months, P = 0.011).

Conclusions: The LNR can be used to select the appropriate adjuvant chemotherapy regimen for patients with D2-resected gastric cancer, particularly in stage III.