Validation of the 9th Edition of the Tumor-Node-Metastasis Staging System for Non-Metastatic Nasopharyngeal Carcinoma: A Multicenter Retrospective Analysis From High-Incidence Regions.

OBJECTIVE: To evaluate and compare the prognostic value of the 8th and 9th editions of the American Joint Committee on Cancer (AJCC)/Union for International Cancer Control (UICC) staging system in patients with non-metastatic nasopharyngeal carcinoma (NPC). METHODS: Clinical data from 470 patients with NPC treated between November 2019 and June 2022 were retrospectively analyzed. Patients were restaged according to the 8th and 9th editions of the AJCC/UICC staging system. OS was the primary endpoint; locoregional recurrence-free survival (LRFS), distant metastasis-free survival (DMFS), and disease-free survival (DFS) were secondary endpoints. Kaplan-Meier curves were compared using global and pairwise log-rank tests. Prognostic discriminative ability was evaluated using the concordance index (C-index) and Akaike information criterion (AIC). RESULTS: Seventeen patients (3.6%) classified as T3 by TNM-8 were reclassified as T4 by TNM-9. Thirty-one patients (6.6%) were reclassified to N3 because of advanced iENE. TNM-9 improved discrimination for DMFS across N categories (log-rank p < 0.001 vs. p = 0.016 for TNM-8) and for OS (p < 0.001 vs. p = 0.042). T categories discriminated LRFS in both editions (p = 0.012 for each), whereas OS differences were not significant (TNM-8 p = 0.139; TNM-9 p = 0.137). TNM-9 overall stage discriminated OS (p = 0.002), unlike TNM-8 (p = 0.121). Both editions discriminated DFS (both p < 0.001), but TNM-9 provided better pairwise separation between early and advanced overall stages. The 9th edition exhibited enhanced predictive performance compared with the 8th edition, as evidenced by higher C-index values and lower Akaike information criterion (AIC) values for both DFS and OS prediction across overall stages. CONCLUSION: The 9th edition of the AJCC/UICC staging system demonstrated superior prognostic discriminative ability compared with the 8th edition, enabling more accurate risk stratification and supporting more informed clinical decision-making for patients with NPC.