Reliability and Validity of Imaging-derived Extranodal Extension Grading Using CT and MRI in Nasopharyngeal Carcinoma.

Background Imaging-derived extranodal extension (iENE) was added to the N3 criteria for nasopharyngeal carcinoma (NPC) in the ninth version of the tumor-node-metastasis (TNM) staging system. Purpose To evaluate the reliability and prognostic value of a proposed joint task force iENE grading system in NPC. Materials and Methods This retrospective single-center study included patients with NPC treated between January 2007 and March 2025. For patients with cervical lymph node metastases, three radiologists independently graded iENE at pretreatment CT and/or MRI using the proposed four-tier classification system. Inter- and intrarater reliability was assessed using the intraclass correlation coefficient (ICC) and weighted κ. Overall survival (OS), disease-free survival, local-regional recurrence-free survival, and distant metastasis-free survival (DMFS) were evaluated across iENE grades using Kaplan-Meier and multivariable Cox regression analyses adjusted for age, sex, T and M categories, and chemotherapy status. Results A total of 401 patients (median age, 52 years [IQR, 44-60 years]; 296 male patients) were included. According to the consensus-based final iENE grades, 223, 36, 94, and 48 patients were classified as having iENE grade 0, 1, 2, and 3, respectively. Interrater reliability (ICC, 0.87 [95% CI: 0.85, 0.89]) and intrarater reliability (κ = 0.95) for iENE grading were excellent. Compared with patients with iENE grade 0, patients with iENE grade 3 had shorter OS (hazard ratio, 3.30 [95% CI: 1.70, 6.41]; P < .001). In addition, patients with iENE grade 1, 2, and 3 had shorter DMFS than patients with iENE grade 0, with hazard ratios of 2.33 (95% CI: 1.12, 4.87; P = .02), 2.11 (95% CI: 1.24, 3.60; P = .006), and 2.39 (95% CI: 1.28, 4.45; P = .006), respectively. There was no evidence of a difference in prognostic performance between the TNM-8 and TNM-9 systems. Conclusion The joint task force iENE grading system had excellent reliability and good prognostic value in patients with NPC. © RSNA, 2026 Supplemental material is available for this article.