Circulating Epstein–Barr virus DNA level post induction chemotherapy contributes to prognostication in advanced-stage nasopharyngeal carcinoma

To investigate the value of post-induction chemotherapy (IC) cell-free Epstein–Barr virus DNA (cfEBV DNApostIC) for prognostication in locally advanced nasopharyngeal carcinoma (LA-NPC). A total of 910 histologically proven LA-NPC undergoing radical IC + concurrent chemo-radiotherapy (CCRT) or targeted radiotherapy (CTRT) or both (CTCRT) were involved. The concentration of cfEBV DNA was measured by quantitative polymerase chain reaction pre-IC (cfEBV DNApreIC) and at IC completion. CfEBV DNApostIC was classified as undetectable (0 copy/ml) and detectable (>0 copy/ml). Recursive partitioning analysis (RPA) with respect to the overall survival (OS) was applied to construct a risk stratification system incorporating cfEBV DNApostIC and critical risk factors. We observed that 660 (72.5%) and 250 (27.5%) patients had cfEBV DNApostIC undetectable and detectable respectively. CfEBV DNApostIC positive was associated with a significant inferior 5-year OS (76.2% versus 85.9%), metastasis-free survival (DMFS, 71.7% versus 86.4%) and disease-free survival (DFS, 57.7% versus 80.1%) than cfEBV DNApostIC negative (P