Clinical scenario of EBV DNA follow-up in patients of treated localized nasopharyngeal carcinoma

In this study, we investigated the usefulness and limitations of EBV-DNA follow-up in patients who had treated localized nasopharyngeal carcinoma. Study subjects comprised 389 patients who had received treatment for localized nasopharyngeal carcinoma in our department. Copy numbers of EBV-DNA in plasma were assessed by real-time quantitative PCR. Patients in whom disease recurrence was suspected underwent image evaluation, esp. PET scan, and tissue proof if it is feasible. Lesions of undermined nature were confirmed by sequential follow-up. Plasma EBV-DNA was detectable in 60 of 63 (95%) patients with metastatic disease and all had positive PET findings. In addition, of the 45 patients with localized recurrent disease, plasma EBV-DNA was detectable in 23 (51%) patients and positive PET scan results were obtained in 40 (89%) of the patients. Of the 284 patients who were disease free, plasma EBV-DNA was detected in 90 (32%) patients. Of the 19 patients in disease free group who were suspected disease recurrence receiving PET scanning, 7 positive PET images were found including 3 second primary malignancy and 4 non-cancer lesions. Two lymphoma cases with positive EBV-DNA value sequentially attacked before or after their NPC were diagnosed. With the cutoff value of 400 copies/ml of EBV-DNA, the positive predict value was 73.5% and the negative predict value was 82.1%. The sensitivity was 0.46 and the specificity was 0.94. EBV-DNA was a good marker for detecting metastatic failure in treated localized NPC. However, careful interpretation with complements from image examination was needed for locoregional failure and other false positive or false negative situations.