Comparison of Epstein-Barr Virus DNA Level in Plasma, Peripheral Blood Cell and Tumor Tissue in Nasopharyngeal Carcinoma

Background: The plasma Epstein-Barr virus DNA (EBV-DNA) level has been found to be an indicator for staging and prognosis of nasopharyngeal carcinoma (NPC). Materials and Methods: The EBV-DNA level in plasma, peripheral blood cells (PBC) and neoplastic tissues was quantitatively analyzed and potential associations with clinical parameters of NPC were investigated. Results: The plasma EBV-DNA detecting rate and level in NPC (92%, 82,500 copies/ml) was significantly higher than that in NPC after treatment (19%, 0 copy/ml) and in controls (12%, 0 copy/ml) (p<0.001); while there was no significance of the PBC EBV- DNA detecting rate and EBV-DNA load in NPC before (24%, 0 copy/actin) and after treatment (14%, 0 copy/actin), and in controls (16%, 0 copy/actin). The plasma EBV-DNA level was not correlated to the PBC EBV-DNA load in NPC before (p=0.92) and after treatment (p=0.267), and in controls (p=0.735). The EBV-DNA level in NPC tumor (27.8 copies/actin) was significantly higher than that in nasopharyngitis and was positively correlated to the ratio of EBER1-positive cells on the NPC section (p=0.001). The plasma EBV-DNA level was significantly increased in TNM stages I, II, III and IV NPC, whereas there was no significant difference of PBC EBV-DNA load in different stage NPC. Conclusion: Our results indicate that plasma EBV-DNA is a more sensitive and reliable biomarker than PBC EBV-DNA for diagnosis, staging and therapeutic effect evaluation at a molecular level in NPC clinical practice. Plasma EBV-DNA may derive from the cancer cells and PBC EBV-DNA from circulating mononuclear cells in NPC patients. The Epstein-Barr virus (EBV) infects both epithelial cells and B lymphocytes in vivo and is associated with malignancies which arise in both cell types, including nasopharyngeal carcinoma (NPC), Burkitt's lymphoma and infectious mononucleosis (1,2). NPC is one of the most common cancers in southern China. EBV infection, genetic