Prognostic effect of residual plasma Epstein–Barr viral DNA after induction chemotherapy for locoregionally advanced nasopharyngeal carcinoma

BACKGROUND: To assess the prognostic effect of plasma Epstein–Barr virus (EBV) DNA load after induction chemotherapy (post(IC)‐EBV DNA) on survival outcomes in locoregionally advanced nasopharyngeal carcinoma (LA‐NPC). METHODS: Patients who were diagnosed with LA‐NPC between August 2017 and October 2021 were included. The chi‐squared test, receiver operating characteristic, Kaplan–Meier survival analysis, and Cox proportional hazard model were used for statistical analysis. RESULTS: We included 172 patients with EBV DNA‐positive LA‐NPC in this study. There were 35.5% (n = 61) of patients had plasma residual EBV DNA after induction chemotherapy (IC). Patients with higher EBV DNA before IC (p < 0.001) and advanced nodal stage (p = 0.031) were significantly related to a higher rate of residual post(IC)‐EBV DNA. Patients with detectable post(IC)‐EBV DNA had inferior 3‐year locoregional relapse‐free survival (LRFS) (86.7% vs. 96.9%, p = 0.020), distant metastasis‐free survival (DMFS) (76.8% vs. 94.2%, p < 0.001), disease‐free survival (DFS) (68.2% vs. 91.1%, p < 0.001), and overall survival (OS) (87.8% vs. 97.9%, p = 0.044) compared to those with undetectable post(IC)‐EBV DNA. The multivariate prognostic analyses showed that detectable post(IC)‐EBV DNA was the independent prognostic factor related to LRFS (p = 0.032), DMFS (p = 0.010), and DFS (p = 0.004) than those with undetectable post(IC)‐EBV DNA. Pretreatment EBV DNA load had no prognostic effect in the multivariate analyses. CONCLUSIONS: The monitoring of plasma post(IC)‐EBV DNA has improved prognostication in LA‐NPC. Our findings suggest that post(IC)‐EBV DNA may be a robust indicator to identify the optimal candidate for intensive treatment.