Correlation of Epstein-Barr virus DNA in cell-free plasma, functional imaging and clinical course in locally advanced nasopharyngeal cancer: a pilot study.

Background: We evaluated the feasibility of using quantitative real-time polymerase chain reaction (PCR) in monitoring Epstein-Barr virus (EBV) DNA concentrations in cell-free plasma of patients with localized nonmetastatic nasopharyngeal carcinoma (NPC) treated with chemoradiation.

Methods: Cell-free plasma EBV DNA was quantified in six patients with locally advanced, nonmetastatic nasopharyngeal cancer (NPC) who underwent chemoradiation therapy (CRT) and correlated with magnetic resonance imaging (MRI), positron emission tomography (PET) scans, and clinical course.

Results: The mean concentration of EBV DNA was 24,610 copies/mL, 682 copies/mL, and 64.5 copies/mL in the pretreatment, posttreatment, and last follow-up samples, respectively. Four of the six patients had normal PET scans and reduction of EBV DNA copy numbers to minimal levels after treatment and, despite equivocal posttreatment MRI scans, are clinically free of recurrent disease. Two of the six patients had elevated EBV DNA copy numbers immediately after treatment, but a metastatic workup was clear at the time; both subsequently relapsed with distant metastases 5 and 11 months later. Although the posttreatment PET scans were abnormal in both of these cases, they were not predictive of the subsequent sites of tumor relapse.

Conclusions: To our knowledge, this is the first report on the correlation between EBV DNA levels and PET scan results in patients with NPC. Reductions in EBV DNA levels and normal PET scans after treatment were consistent among patients who had residual abnormality on MRI images. Persistently elevated EBV DNA levels and abnormal PET scans after treatment suggest residual disease. Further evaluations are required to determine the relative contributions of these two novel techniques in predicting residual disease in locally advanced NPC.