Risk stratification of advanced extranodal extension in retropharyngeal lymph nodes for nasopharyngeal carcinoma: a multi-center study

This study aimed to refine risk stratification of advanced extranodal extension (ENE) in retropharyngeal lymph nodes (RLNs) and evaluate its prognostic significance. A total of 1,373 non-metastatic NPC patients at three centers between 2011 and 2021 were retrospectively enrolled. For advanced RLN ENE, we documented all involved structures, maximum axial diameter (MAD), presence of lymph node necrosis (LNN), and bilaterality. High-risk structures were identified using adjusted hazard ratios and LASSO-Cox models. Multivariable Cox models and Kaplan-Meier analyses were used to evaluate associations with survival outcomes. Of the 1,373 patients, 1061 had RLN metastasis, including 168 with advanced RLN ENE. Involvement of interval structures, the lower cranial nerves region, internal jugular vein, and longus capitis muscle was classified as high-risk, whereas isolated internal carotid artery involvement was low-risk. Advanced RLN ENE with high-risk structure involvement or LNN was defined as high-risk RLN ENE. High-risk RLN ENE was an independent adverse prognostic factor for NPC. N1/N2 patients with high-risk RLN ENE showed survival comparable to N3 disease. High-risk RLN ENE is an independent adverse prognostic factor in NPC. N1/N2 patients with high-risk RLN ENE exhibit N3-like survival, supporting its potential incorporation into future refinements of N staging.