This study was dedicated to investigate the predictive value of pre- and post-induction chemotherapy plasma EBV (Epstein-Barr Virus) DNA level and tumor volume for the radiosensitivity of locally advanced NPC. 129 previously untreated locally advanced NPC patients were enrolled. Plasma EBV-DNA copy number and tumor volume was detected before and after induction chemotherapy. The tumor volume was also measured after radiotherapy. Among 129 patients, 98 were positive for EBV DNA. The residual gross target volume of the primary tumor (GTVnx) and GTVnd after radiotherapy was positively correlated with post-induction chemotherapy EBV copy number (rho=0.357, P<0.001; rho=0.356, P<0.001, respectively). Univariate logistic regression analyses showed that the AUC of ROC curves of post-induction chemotherapy tumor volume, tumor regression rate before and after induction chemotherapy, post-induction EBV copy number, EBV decrease rate for predicting no residual nasopharyngeal tumor were 0.859, 0.782, 0.678 and 0.657, respectively. Multivariate logistic analyses showed that T stage, post-induction chemotherapy EBV copy number and tumor volume were independent predictors for no residual nasopharyngeal tumor after radiotherapy. The changes in plasma EBV DNA and tumor volume during treatment could be used to predict the sensitivity of locally advanced NPC patients in response to intensity-modulated radiation therapy (IMRT).
Keywords: Epstein-Barr virus; induction chemotherapy; intensity-modulated radiation therapy; logistic regression; nasopharyngeal carcinoma; radiosensitivity.