Prognostic Value and Staging Classification of Lymph Nodal Necrosis in Nasopharyngeal Carcinoma after Intensity-Modulated Radiotherapy

PURPOSE: The aim of the present study was to evaluate the prognostic value of magnetic resonance imaging (MRI)‒determined lymph nodal necrosis (LNN) in nasopharyngeal carcinoma (NPC) and explore the feasibility of an N-classification system based on the 8th edition of the American Joint Committee on Cancer (AJCC) system. MATERIALS AND METHODS: The MRI scans of 616 patients with newly diagnosed stage T1-4N1-3M0 NPC who were treated with definitive intensity-modulated radiotherapy (IMRT) were reviewed. RESULTS: Multivariate analysis showed that LNN was an independent negative prognostic predictor of distant metastasis free survival (hazard ratio, 1.634; 95% confidence interval, 1.023 to 2.609; p=0.040) and overall survival (hazard ratio, 2.154; 95% confidence interval, 1.282 to 3.620; p=0.004). Patients of classification N1 disease with LNN were reclassified as classification N2, and classification N2 disease with LNN as classification N3 in the proposed N-classification system. Correlation with death and distant failure was significant, and the total difference between N1 and N3 was wider with the proposed system. CONCLUSION: MRI-determined LNN is an independent negative prognostic factor for NPC. The proposed N classification system is powerfully predictive.