3501 - Validation and Refinement of the AJCC/UICC TNM-9 M1 Category in Metachronous Metastatic Nasopharyngeal Carcinoma: A Recursive Partitioning Analysis for Improved Risk Stratification
Presenter(s)
D. Huang1, H. Xu1, X. Xie1, Y. Huang1, K. Lin1, Y. Huang1, L. Zhu1, Y. Zheng1, C. Huang1, Y. Xiao2, J. Pan1,3, S. Lin1,3, J. WU1,3, and Q. Guo1,3; 1Department of Radiation Oncology, Clinical Oncology School of Fujian Medical University, Fujian Cancer Hospital, Fuzhou, Fujian, China, 2Department of Radiology, Clinical Oncology School of Fujian Medical University, Fujian Cancer Hospital, Fuzhou, Fujian, China, 3Fujian Key Laboratory of Translational Cancer Medicine, Fuzhou, Fujian, China
Purpose/Objective(s):
To validate the prognostic value of the M1 category in version nine of the AJCC/UICC TNM staging system (TNM-9) in metachronous metastatic nasopharyngeal carcinoma (mmNPC) and to develop a refined M1 classification for improved risk stratification.
Materials/Methods:
Patients with newly diagnosed mmNPC (2015–2024) were analyzed and restaged per TNM-9 M1 criteria. Independent prognostic factors from multivariate Cox analysis were integrated using recursive partitioning analysis (RPA) to establish an RPA-based M1 classification (RPA-M1). Model performance was assessed using Harrell's C-index, time-dependent AUC, and Akaike information criterion.
Results:
Among 218 patients, 111 (50.9%) were M1a and 107 (49.1%) M1b. The M1a subgroup demonstrated significantly higher 3-year overall survival (OS) than the M1b subgroup (63.2% vs. 40.8%, P < 0.001). Both the TNM-9 M1 category and disease-free interval (DFI) were independent prognostic factors for OS (both P < 0.05). The RPA model stratified patients into distinct prognostic groups: RPA-M1a (= 3 metastatic lesions and DFI > 12 months) and RPA-M1b (> 3 lesions or DFI = 12 months), with 3-year OS rates of 74.6% and 40.6%, respectively (P < 0.001). The RPA-M1 classification showed superior prognostic discrimination compared with the TNM-9 M1 stage, evidenced by higher harrell’s concordance index (C-index), time-dependent AUCs, and lower akaike information criterion (AIC). Metastasis-directed therapy improved OS only in the RPA-M1a subgroup, while intensified systemic therapy primarily benefited the RPA-M1b subgroup.
Conclusion:
The TNM-9 M1 category is applicable to mmNPC. The novel RPA-M1 classification, which integrates metastatic burden and DFI, offers superior risk stratification and enables more precise prognostication and individualized management.