Evaluation of the Eighth Edition of the American Joint Committee on Cancer TNM Staging System for Gastric Cancer: An Analysis of 7371 Patients in the SEER Database

Abstract

Objective: To investigate the validity of the 8^th edition of the American Joint Committee on Cancer (AJCC) TNM staging system for gastric cancer.

Methods: The clinicopathologic data of 7371 patients who were diagnosed with gastric cancer and had 16 or more involved lymph nodes (LNs) were retrieved from the Surveillance, Epidemiology, and End Results (SEER) database and retrospectively reviewed.

Results: Stage migration occurred primarily during stage III between the 7^th and 8^th edition TNM staging systems. Stages IIIB and IIIC in the 7^th edition staging system were divided in the 8^th edition and had obvious differences in survival rates (both P < 0.001). The 8^th edition TNM stages IIIC and IV showed similar survival rates (P = 0.101). The prognosis of patients with T4aN3bM0 was not different from that of patients with TxNxM1 (P = 0.433), while the prognosis of patients with T4bN3bM0 was significantly poorer than that of patients with TxNxM1 (P = 0.008). A revised TNM system with both T4aN3bM0 and T4bN3bM0 incorporated into stage IV was proposed. Multivariable regression analysis showed that the revised TNM system, but not the 7^th and 8^th editions, was an independent factor for disease-specific survival (DSS) in the third step of the analysis. Further analyses revealed that the revised TNM system had superior discriminatory ability to the 8^th edition staging system, which was also an improvement over the 7^th edition staging system.

Conclusion: The 8^th edition of the AJCC TNM staging system is superior to the 7^th edition for predicting the DSS rates of gastric cancer patients. However, for better prognostic stratification, it might be more suitable for T4aN3bM0/T4bN3bM0 to be incorporated into stage IV in the 8^th edition TNM staging system.

Figure 1

Comparison of survival curves. (a) According to the 8^th edition T category. (b) According to the 8^th edition N category. (c) According to the 7^th edition AJCC TNM stage. (d) According to the 8^th edition AJCC TNM stage.

Figure 2

Five-year survival rates according to the 8^th edition T and N categories.

Figure 3

Comparison of survival curves based on the 8^th edition staging system. (a) Among T4bN3aM0/T4bN3bM0/T4aN3bM0/T3N3bM0/TxNxM1. (b) Between T4bN3aM0/T4aN3bM0/T3N3bM0 and T4bN3bM0/TxNxM1 (HR: 1.047, 95% CI: 1.020-1.076, P = 0.001). (c) Between T4bN3aM0/T3N3bM0 and T4aN3bM0/T4bN3bM0/TxNxM1 (HR: 1.062, 95% CI: 1.029-1.097, P < 0.001). (d) Between T4bN3aM0 and T4aN3bM0/T4bN3bM0/T3N3bM0/TxNxM1 (HR: 1.048, 95% CI: 0.993-1.106, P = 0.089).