Residual plasma Epstein–Barr virus DNA after intensity-modulated radiation therapy is associated with poor outcomes in nasopharyngeal carcinoma

Aim: To investigate the effects of residual plasma Epstein-Barr virus (EBV) DNA levels after 3 months of intensity-modulated radiation therapy (IMRT) (postIMRT-EBV DNA) on prognosis in patients with nasopharyngeal carcinoma. Methods: Data from 300 patients were retrospectively collected for analysis. Results: Of these patients, 25 (8.3%) and 275 (91.7%) had positive and negative postIMRT-EBV DNA, respectively. Multivariate survival analysis showed that EBV DNA >688 IU/ml was independently associated with inferior distant metastasis-free survival (p = 0.003) and progression-free survival (p = 0.002). Moreover, postIMRT-EBV DNA was independently associated with inferior locoregional recurrence-free survival (hazard ratio: 4.325; p = 0.018), distant metastasis-free survival (hazard ratio: 10.226; p < 0.001) and progression-free survival (hazard ratio: 10.520; p < 0.001). Conclusion: Positive postIMRT-EBV DNA is a prognostic biomarker for nasopharyngeal carcinoma.