Epstein–Barr Virus (EBV) Viral Load in Tumor Cells Did Not Predict Tumor Extensiveness in Nasopharyngeal Cancer

Abstract

Background: Nasopharyngeal cancer is commonly associated with Epstein–Barr virus (EBV) infection, especially undifferentiated non-keratinized histology. EBV DNA quantification through nasopharyngeal brushing was previously reported to be not related to disease stage. This study aimed to reinvestigate the relationship of EBV viral load in tumor tissue with tumor extensiveness by more accurate EBV DNA quantification through microscopically confirmed tumor cells from nasopharyngeal biopsy. Method: The specimens for EBV DNA quantification were derived from histopathology slides which were pre-treated following the QIAsymphony® SP protocol for tissue DNA extraction. Then, the extracted DNA underwent real-time polymerase chain reaction (RT-PCR) using the artus® EBV RG PCR Kit for EBV DNA quantification. The tumor volume was determined by delineating the gross tumor based on 3D imaging of the patient’s nasopharynx. Result: Twenty-four subjects were included in this study. All subjects were stage III and above, with more males (75%) than females. EBV viral load in tumor cells was found to have no correlation to tumor volume both in local and nodal regions. The median local tumor volume was 81.3 cm3 ± 80 cm3. The median EBV viral load in tumor cells was 95,644.8 ± 224,758.4 copies/100 ng of DNA. The median nodal or regional tumor volume was 35.7 ± 73.63 cm3. Conclusion: EBV viral load from tumor cells from nasopharyngeal biopsy has no relationship with tumor extensiveness in nasopharyngeal cancer. The presence and amount of EBV in tumor cells did not translate into larger or smaller tumors. The EBV viral proteins and RNAs were perhaps more likely to confer some prognostic information due to the fact that those molecules were related to carcinogenesis.