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

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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.