Epstein-Barr virus DNA in serum/plasma as a tumor marker for nasopharyngeal cancer

Nasopharyngeal cancer (NPC) constitutes a type of carcinoma encountered fre quently in Southern China, among Eskimos of the Arctic region, and to a les ser extent in Southeast Asia. Because EBV DNA present in plasma or serum of NPC patients has proven to represent a promising noninvasive tumor marker, the present study was designed to determine the incidence of serum/plasma EBV DNA by nested PCR during various disease management stages. By this met hod, we could detect EBV DNA in plasma/serum of 98 of 167 NPC patients prio r to treatment, compared with 10 of 77 samples derived from healthy blood d onors serving as controls, with a similar prevalence observed in plasma ver sus serum. Investigation of 13 patients subjected to radiotherapy revealed plasma EBV DNA to persist in the plasma of one case, whereas among the rema ining patients, it had vanished during the early phase of treatment. Finall y, with 52 samples derived from 37 NPC patients during follow-up, we establ ished 100% specificity and 0% false-positive rate for plasma DNA detection by nested PCR, Moreover, we subjected 24 known EBV DNA-positive serum sampl es to DNase digestion prior to DNA extraction and amplification to differen tiate between free and encapsulated viral DNA, which demonstrated complete absence of the human beta-globin genomic DNA in contrast to EBV DNA detecta ble in 14 samples. In conclusion, applying this noninvasive method, serum/p lasma EBV DNA constitutes a reliable tumor marker prior to, during, and aft er treatment of NPC.