Evaluation of plasma Epstein-Barr virus DNA load as a prognostic marker for nasopharyngeal carcinoma

Tan EL, Looi LM, Sam CK
Correspondence: Dr Tan Eng Lai, englaitan@gmail.com

ABSTRACT
Introduction Nasopharyngeal carcinoma (NPC) is an important cancer in Malaysia and is one of the major causes of cancer mortality in this country. This study evaluates the diagnostic and prognostic values in the quantitative relationship between the cell-free Epstein-Barr virus (EBV) deoxyribonucleic acid (DNA) load and the tumour burden.
Methods Blood plasma from 18 untreated NPC patients, 20 NPC patients who had been treated with radiotherapy, and 12 healthy individuals were evaluated. EBV copy number was determined following DNA extraction using real-time quantitative polymerase chain reaction.
Results The cell-free EBV DNA load was shown to be proportionately related to the presence of malignant disease. While the EBV copy number in untreated NPC patients had a median of 2,043 copies/ml, viral load in plasma of healthy controls was significantly lower (median of 0 copy/ml). A significant decrease in EBV load was observed in patients who had undergone radiotherapy while a high viral load indicated in one patient correlated to tumour relapse and presence of distant metastasis upon clinical investigation.
Conclusion The blood plasma EBV DNA load was shown to be proportionately related to the presence of malignant disease. This preliminary study underscores the prognostic value of cell-free EBV DNA quantification.

Keywords: DNA, Epstein-Barr virus, human herpes virus, nasopharyngeal carcinoma
Singapore Med J 2006; 47(9): 803-807