S594
Clinical – Head & neck
ESTRO 2026
Purpose/Objective: The 9th edition AJCC/UICC staging system for
nasopharyngeal carcinoma (NPC) has not incorporated extranodal extension (ENE) of retropharyngeal lymph nodes (RLNs)[1]. This study aimed to refine risk stratification of advanced RLN ENE and evaluate its prognostic significance. Material/Methods: A total of 1,174 non-metastatic NPC patients at two centers between 2011 and 2021 were retrospectively enrolled. For advanced RLN ENE, we documented involved structures—including the longus capitis muscle, internal carotid artery, internal jugular vein, lower cranial nerves, and interval structures (medial pterygoid muscle, mandibular nerve, external carotid artery, vertebral vessels)—as well as maximum axial diameter, presence of necrosis, and bilaterality. High- risk structures were identified using adjusted hazard ratios (AHRs) and least absolute shrinkage and selection operator (LASSO)–Cox models. Multivariable Cox models adjusted for confounding factors and Kaplan-Meier (KM) curves were used to evaluate the correlations between nodal features and overall survival (OS), progression-free survival (PFS), locoregional relapse-free survival (LRRFS), and distant metastasis-free survival (DMFS). Results: Of the 1,174 patients, 905 (77.1%) had RLN metastasis, including 197 (21.7%) with advanced RLN ENE. Based on ranked AHRs, involvement of interval structures (AHR = 6.69), lower cranial nerves (AHR = 4.36), internal jugular vein (AHR = 4.05), and longus capitis muscle (AHR = 3.40) was classified as the high-risk structure group, whereas isolated internal carotid artery involvement (AHR = 1.46) was assigned to the low-risk group; these findings were supported by the LASSO–Cox model. In multivariable analyses, advanced RLN ENE with involvement of high-risk structures (OS: AHR = 1.78, 95% CI: 1.17–2.72; p = 0.007) or necrosis (OS: AHR = 1.76, 95% CI: 1.03–3.00; p = 0.037) was associated with significantly worse survival. Advanced RLN ENE with high-risk structure involvement and/or necrosis was therefore defined as high-risk RLN ENE. High-risk RLN ENE was an independent adverse prognostic factor for NPC (OS: AHR = 1.70, 95% CI: 1.15–2.51; p = 0.008; PFS: AHR = 1.49, 95% CI: 1.09–2.05; p = 0.013). N1/N2 patients with high-risk RLN ENE had survival outcomes comparable to those of N3 patients ( OS: AHR = 0.66, 95% CI: 0.36– 1.20; p = 0.169; OS: AHR = 0.84, 95% CI: 0.46–1.56; p = 0.589).
Conclusion: In this cohort of pathologically proven mandibular ORN, radiomic analysis identified three CT-derived features potentially associated with coexisting tumor recurrence. Despite limited statistical power, these findings highlight the potential of radiomics to capture imaging heterogeneity within necrotic tissue and motivate the development of multicentric studies to validate predictive models integrating clinical, dosimetric, and metabolic data Keywords: Osteoradionecrosis, recurrence, radiomics, Digital Poster Highlight 2292 Risk Stratification of Advanced Extranodal Extension in Retropharyngeal Lymph Nodes for Nasopharyngeal Carcinoma: A Dual-Center Study junyi liu, bolin lu, tong jin, tong bu, Lirong Wu, xia he Department of Radiation Oncology, Jiangsu Cancer Hospital & Jiangsu Institute of Cancer Research & Affiliated Cancer Hospital of Nanjing Medical University, Nanjing, China
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