S604
Clinical – Head & neck
ESTRO 2026
Material/Methods: We retrospectively analyzed LA-NPC patients identified within a retrospective cohort of 1,401 newly diagnosed non-metastatic (M0) NPC patients treated at three cancer centers in Jiangsu, Zhejiang and Anhui from 2011 to 2023. Outcomes included overall survival (OS), locoregional relapse-free survival (LRFS), distant metastasis-free survival (DMFS) and progression-free survival (PFS)2. Survival curves were estimated by Kaplan-Meier analysis and compared with log-rank tests. Prognostic variables were evaluated with Cox proportional hazards Models using bootstrap resampling. Candidate subgroup schemes were compared by concordance index (C-index), AUC, AIC
and BIC. Results:
Survival analysis based on TNM-9 demonstrated clear separation of survival curves across stages (P < 0.001). The 5- and 10-year OS rates were 93.4% and 75.8% for stage Ⅱ versus 78.6% and 68.4% for stage Ⅲ . For distant control, 5- and 10-year DMFS were 90.6% and 87.7% for stage Ⅱ compared with 73.3% and 69.5% for stage Ⅲ (P < 0.001). However, TNM-9 showed limited discrimination within locally advanced subgroups (e.g., C-index for original Ⅱ / Ⅲ comparison ≈ 0.383). To address this, we derived three survival-quantile–based subgrouping schemes (Categories A, B and C). All three Categories produced meaningful risk separation and outperformed TNM-9: Category A (median dichotomization) achieved C-index = 0.631; Category B (three-tier grouping) yielded C-index range 0.524– 0.592 across datasets; Category C (extreme dichotomization, OS ≥ 90% vs ≤ 80%) achieved the highest discrimination with C-index = 0.700 in the total cohort, 0.684 in internal cohort and 0.674 in external cohort. Hazard ratios (high- vs low-risk) progressively increased across Categories (Category A HR = 2.96; Category B HR = 3.99; Category C HR = 4.70), confirming stronger risk separation. In multivariable analyses, subgroup risk and older age were independent adverse prognostic factors (age: 3.6%–4% increased risk per year), while targeted therapy consistently conferred protection (HR range 0.51–0.66 across Categories).
Conclusion: TNM-9 affords robust prognostic stratification for locally advanced NPC in non-high-incidence regions of China. Notable intra-stage heterogeneity supports refined subgroup stratification to guide individualized management. References: [1] Pan JJ, Mai HQ, Ng WT, et al. Ninth Version of the AJCC and UICC Nasopharyngeal Cancer TNM Staging Classification. JAMA Oncol.2024;10(12):1627.doi:10.1001/jamaoncol.2024.4 354[2] Zhong J, Chen H, Chen X, et al. Identifying adverse nodal features associated with poor prognosis in stage IB nasopharyngeal carcinoma patients based on the 9th AJCC/UICC staging system: Implications for treatment intensification. Radiother Oncol. 2025;205:110747. doi:10.1016/j.radonc.2025.110747 Keywords: TNM staging, subgroup stratification
Digital Poster 2844
VMAT Lattice Radiotherapy in Bulky Head-and- Neck Tumors: Dosimetric Analysis and Clinical Outcomes Diego Rodolfo Fernandez, Lucas Caussa, Belen Raiden, Ivan Charif, Camila Vargas, Fernanda Diaz Vazquez, Gustavo Ferraris, Caroline Descamps Radiotherapy, Centro medico Dean Funes, Cordoba, Argentina
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