Prognostic Impact of Plasma Epstein-Barr Virus DNA in Patients with Nasopharyngeal Carcinoma Treated using Intensity-Modulated Radiation Therapy

The prognostic value of plasma Epstein-Barr virus (EBV) DNA remains unknown in nasopharyngeal carcinoma (NPC) treated with intensity-modulated radiation therapy (IMRT). We retrospectively reviewed medical records of 584 newly diagnosed patients with nonmetastatic and biopsy-proven NPC treated using IMRT. Plasma EBV DNA concentration was measured before therapy (pre-DNA) and within 1 month of completing therapy (post-DNA) using real-time quantitative polymerase chain reaction. Receiver operating characteristic (ROC) curves were generated to identify pre-DNA and post-DNA cut-off values. Prognostic value was assessed using a multivariate Cox proportional hazards model .Three-year disease-free survival (DFS), overall survival (OS), loco-regional relapse-free survival (LRRFS) and distant metastasis-free (DMFS) for pre-DNA >2010 vs.≤2010 were 78.1% vs. 93.6% (P < 0.001), 92.3% vs. 98.9% (P < 0.001), 90.9% vs. 96.6% (P = 0.004) and 85.5% vs. 96.6% (P < 0.001), respectively. Three-year DFS, OS, LRRFS and DMFS for post-DNA >0 vs. = 0 were 49.9% vs. 88.5% (P < 0.001), 72.1% vs. 97.5% (P < 0.001), 86.6% vs. 94.3% (P = 0.019), and 60.5% vs. 93.3% (P < 0.001), respectively. Plasma EBV DNA remains a prognostic factor in IMRT era and should be incorporated into TNM staging to guide individualized treatment strategies in NPC.