[Quantitative analysis of plasma Epstein-Barr virus (EBV) DNA for monitoring of recurrence and metastasis in nasopharyngeal carcinoma patients after radiotherapy].

BACKGROUND & OBJECTIVE: Nasopharyngeal carcinoma (NPC) is closely related to Epstein-Barr virus (EBV) infection. Recently, it was reported that EBV DNA could be detected in the plasma or serum of NPC patients, but the clinical significance of EBV DNA concentration for monitoring of tumor recurrence and metastasis in NPC patients after radiotherapy has not been reported. This study was designed to quantitatively analyze the plasma EBV DNA concentration in NPC patients after radiotherapy, and to evaluate its application for monitoring of tumor recurrence and metastasis. METHODS: Ninety NPC outpatients after radiotherapy in Cancer Center, Sun Yat-sen University were followed up. The plasma EBV DNA were analyzed by using fluorescent quantitative PCR technique, and the quantity of plasma EBV DNA were compared between recurrent and clinical remission NPC patients. RESULTS: Ninety-six point seven percent (29/30) of recurrent and metastatic patients were detectable for plasma EBV DNA, with median concentration of 2650 copies/ml (range:0-5900000), whereas only 12%(7/60) of the clinical remission patients were detectable for plasma EBV DNA, with median concentration of 0 copy/ml (range:0-71000). The detectable proportion and concentration in recurrent and metastatic NPC patients were significantly higher than that in clinical remission NPC patients (P< 0.01). Three of the clinical remission NPC patients with elevated EBV DNA copy were confirmed for tumor local recurrence or metastasis after further 3-4 month follow-up. CONCLUSION: The results suggest that plasma EBV DNA detection may be a sensitive tumor marker for monitoring tumor recurrence and metastasis of NPC patients after radiotherapy.