Significance of Cell-Free Epstein-Barr Virus DNA in Monitoring Prognosis of Nasopharyngeal Carcinoma

OBJECTIVE It has been reported that cell-free Epstein-Barr virus (EBV-DNA) in plasma was useful in diagnosing and monitoring nasopharyngeal carcinoma (NPC), The current study was designed to evaluate the significance of EBV-DNA in monitoring the prognosis of nasopharyngeal carcinoma and comparing its significance with that of plasma VCA/lgA and EA/IgA levels.

METHODS E8V-DNA, VCA/lgA, and EA/lgA levels in plasma were determined in NPC patients with different prognosis after radiotherapy, including 30 distant metastatic patients, 22 local recurrence patients and 24 individuals with remission who had been followed-up for more than 2 years after treatment. EBV-DNA was determined using a real-time quantitative PCR system, and levels of VCA/lgA and EA/lgA were measured using standard immunofluorescence. In a cohort study, the indexes were determined after different radiation periods for the 20 new cases of nasopharyngeal carcinoma.

RESULTS The median plasma EBV-DNA concentration was 135,100 copies/ ml (interquartile range: 5,525-1,003 750) in metastatic group, 20,500 copies/ ml (interquartile range: 0-58,500) in the local recurrence group and 0 copies/ml (interquartile range: 0-0) in the continuous remission group (P< 0.05). The levels of VCA/lgA and EA/lgA showed no significant differences among the different groups. The high level of EBV-DNA concentration in the metastatic group was more than that in the local recurrence group. A level of 1,000,000 copies/ml of EBV DNA was an indication of distant metastasis of the NPC patients with a sensitivity of 27.3%. However, the sensitivity was 0 in the local recurrence group. For the 20 new patients, EBV-DNA concentration gradually decreased during the radiation period. Before radiation there were 32,050 copies/ml (interquartile range: 3,880-317.750), 0 copies/ml (interquartile range: 0-14 375) after a 40 Gy radiation dose and 0 copies/ml (interquartile range: 0-2940) after the radiation was finished (P< 0.05). However, the levels of VCA/lgA and EA/lgA showed no significant difference.

CONCLUSION Determination of plasma cell-free EBV-DNA level is more valuable than evaluation of VCA/lgA and EA/lgA for monitoring the prognosis of NPC patients.