Prognostic value of radiologic extranodal extension and its potential role in future N classification for nasopharyngeal carcinoma

Abstract Purpose We evaluated the prognostic value of various grades of radiologic extranodal extension (rENE) and their potential roles in N-classification refinement for nasopharyngeal carcinoma (NPC). Methods and Materials All NPC patients treated with IMRT in our institution between 2005 and 2011 were included. Pre-treatment MR of cN+ cases were reviewed and rENE was recorded asG0: lymph nodes (LNs) without rENE; G1: tumor infiltrating beyond individual nodal capsule(s) into the surrounding fat plane; G2: coalescent nodal mass with unequivocal evidence of rENE; G3: tumor infiltrating beyond nodal capsule into adjacent structures. Multivariable analysis (MVA) assessed prognostic value of rENE for distant metastasis (DM) and death adjusted for age, gender, LDH, T-classification, N-classification, and chemotherapy cycles. Results A total of 1390 of 1616 (86%) NPC were cN+, and rENE was detected in 826/1390 (59%) patients: 256 (18.4%) G1-rENE, 487 (35%) G2-rENE, and 83 (6%) G3-rENE. MVA confirmed that G2-/G3-rENE had increased risk of DM (HR: 2.05/3.18, both p  Conclusions G2- and G3-rENE are independently prognostic for DM and death in NPC. Compared to the TNM8 N-classification, a refined N-classification incorporating G2- and G3-rENE improves prognostication of DM and mortality risk.