Clinical evaluation of lymph node metastasis in gastric cancer defined by the fifth edition of the TNM classification in comparison with the Japanese system

Background: This study compared the classification of lymph node metastasis according to the number of involved nodes based on the new tumour node metastasis (TNM) system (fifth edition) with the classification by the Japanese Research Society for Gastric Cancer from an anatomical perspective. Methods: The two classifications were related to long-term results in 1489 patients with gastric cancer who underwent gastrectomy with systematic extended lymphadenectomy. Results: Both classifications performed well as prognostic indicators (5-year survival rates: pathological (p) N-0, 89 per cent; pN(1), 66 per cent; pN(2), 34 per cent; pN(3), nil; and M-1, 10 per cent by the TNM classification; n0, 89 per cent; n1, 63 per cent; n2, 46 per cent; n3, 20 per cent; and n4, 8 per cent by the Japanese classification). For regional lymph nodes, the TNM classification was a better index of the prognosis. Significant survival differences were observed among patients with M1 disease according to the number of involved lymph nodes (between one and six nodes, 48 per cent; seven to 15 nodes, 12 per cent; more than 15 nodes, 2 per cent), indicating that patients with distant metastatic lymph nodes (M1) should also be classified by the number of involved nodes. On the other hand, the Japanese classification has the added benefit of being a good indicator of the anatomical extent of lymphadenectomy. Conclusion: The new TNM classification provided a better index of the prognosis of patients who underwent systematic lymph node dissection. However, both classifications have specific benefits in the surgical treatment of gastric cancer.