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

•CfEBV DNApostIC positive was independently risk for metastasis/death in LA-NPC.•We constructed a cfEBV DNApostIC-based risk classification system in LA-NPC.•Risk stratification is superior to TNM schema in predicting death and metastasis.