Multicenter Validation Study of the American Joint Commission on Cancer (8th Edition) for Gastric Cancer: Proposal for a Simplified and Improved TNM Staging System

Objective: To evaluate the prognostic significance of the eighth edition of the American Joint Committee on Cancer (AJCC) TNM staging classification for gastric cancer. Methods: Prospective databases were reviewed to identify patients who underwent radical gastrectomy at two specialized eastern centers. The prognostic value of the eighth edition TNM classification was estimated and compared with that of the seventh edition. Additional external validation was performed using a dataset from a Western population. Results: Significant differences in 5-year overall survival (OS) rates were observed for each TNM stage when using the eighth edition system, and smaller Akaike information criteria (AIC) values and a higher c-statistic were observed relative to those of the seventh edition. However, the OS rates in each subgroup of stage III patients based on the eighth edition were significantly different. Patients with the same pN stage, namely, the pT4a and pT4b groups, showed similar 5-year OS (P>0.05). Based on the survival data, we propose a simplified staging system. In the improved TNM (iTNM) staging system, the subgroups of a given TNM stage do not show statistically significant differences in OS. The iTNM staging exhibits superior prognostic stratification, with lower AIC values and a higher c-statistic than the eighth edition TNM classification. Similar results were obtained with the external validation dataset from the IMIGASTRIC database. Conclusion: The prognostic prediction of the eighth edition of the AJCC TNM classification is superior to that of the seventh edition. However, it remains associated with some stage migration. The iTNM staging system permits simplification and slightly better prognostic prediction.