Integrating Postradiotherapy MRI-Detected Lymph Node Necrosis and Pre- and Posttreatment Epstein-Barr Virus-DNA for Risk Stratification in Nasopharyngeal Carcinoma.

BACKGROUND: Residual lymphadenopathy and detectable Epstein-Barr virus (EBV) DNA after radiotherapy (RT) are known negative prognostic factors for nasopharyngeal carcinoma (NPC). However, there is a need to distinguish between patients with residual disease that will metastasize and those who will not. PURPOSE: To develop a prognostic model to improve the risk stratification of NPC patients after RT. STUDY TYPE: Retrospective. POPULATION: Three hundred eighty-seven NPC patients treated with RT between January 2010 and January 2013. FIELD STRENGTH/SEQUENCE: T1-, T2-weighted and enhanced T1-weighted imaging at 1.5 or 3.0 T pretreatment and 3-4 months post-RT. ASSESSMENT: Post-RT central nodal necrosis (CNN) and other nodal characteristics on MRI were assessed by three radiologists independently. EBV DNA was measured by quantitative polymerase chain reaction. The association between these variables and the primary endpoint (5-year distant metastasis-free survival [DMFS], time from the day of diagnosis to any distant metastasis) was analyzed. Nomograms A (pre-/posttreatment EBV-DNA + N stage + post-RT retropharyngeal lymph node [RLN] CNN), B (tumor-node-metastasis [TNM] stage + pretreatment EBV-DNA), and C (TNM stage + post-RT EBV-DNA) were developed. STATISTICAL TESTS: Univariate and multivariate analyses were performed with the Cox regression model. Nomograms were developed based on the Cox regression model and two prognostic models. The concordance index (C-index) and calibration curve were used to evaluate the discriminative ability of the nomograms and TNM stage. P-values < 0.05 were considered statistically significant. RESULTS: Post-RT RLN CNN was an independent prognostic factor for 5-year DMFS (hazard ratio, 2.88 [1.48-5.62]). Nomogram A (C-index 0.728 [0.660-0.797]) demonstrated better risk discrimination than nomogram B (0.638 [0.571-0.705]), nomogram C (0.707 [0.636-0.778]), and the TNM stage (0.587 [0.515-0.659]) for 5-year DMFS in NPC. DATA CONCLUSION: Nomogram A combining pretreatment EBV-DNA and N stage with post-RT EBV-DNA and RLN CNN improved the prognostic risk stratification for DMFS in NPC. EVIDENCE LEVEL: 4 TECHNICAL EFFICACY: Stage 2.