Background The identification of effective prognosis biomarkers for nasopharyngeal carcinoma (NPC) is crucial to improve treatment and patient outcomes. In the present study, we have attempted to evaluate the correlation between pre-treatment plasmatic Epstein-Barr virus (EBV) DNA load and the conventional prognostic factors in Moroccan patients with NPC. Methods The present study was conducted on 121 histologically confirmed NPC patients, recruited from January 2017 to December 2018. Circulating levels of EBV DNA were measured before therapy initiation using real-time quantitative PCR. Results Overall, undifferentiated non-keratinizingcarcinoma type was the most common histological type (90.1 %), and 61.8 % of patients were diagnosed at an advanced disease stage (IV). Results of pre-treatment plasma EBV load showed that 90.9 % of patients had detectable EBV DNA, with a median plasmatic viral load of 7710 IU/ml. The correlation between pre-treatment EBV DNA load and the conventional prognostic factors showed a significant association with patients’ age (p = 0.01), tumor classification (p = 0.01), lymph node status (p = 0.003), metastasis status (p = 0.00) and overall cancer stage (p = 0.01). Unexpectedly, a significant higher level of pre-treatment EBV DNA was also found in plasma of NPC patients with a family history of cancer (p = 0.04). The risk of NPC mortality in patients with high pretreatment EBVDNA levels was significantly higher than that of those with low pre-treatment plasma EBV-DNA levels (p < 0.05). Furthermore, patients with high pre-treatment EBV-DNA levels (≥ 2000, ≥ 4000) had a significant low overall survival (OS) rates (p < 0.05). Interestingly, lymph node involvement, metastasis status and OS were found to be the most important factors influencing the EBV DNA load in NPC patients. Conclusions The results of the present study clearly showed a high association between pre-treatment EBV DNA load, the crucial classical prognostic factors (T, N, M and disease stage) of NPC and OS, suggesting that pre-treatment EBV DNA can be a useful prognostic biomarker in clinical decision-making and improving NPC treatment in Morocco.

The current study was designed to investigate the changes in the circulating Epstein–Barr virus DNA load (EBV DNA) at various time points before and after treatment and its clinical significance in nasopharyngeal carcinoma (NPC). A total of 142 patients with NPC were prospectively enrolled in this study. The plasma EBV DNA concentration was measured before and after treatment using qPCR. The prognostic values of the EBV DNA load were analyzed using the Kaplan–Meier and Cox regression tests. Following multivariate analysis, our data showed that high pre-EBV DNA loads were associated with significantly poorer distant metastasis free survival (DMFS) and progression free survival (PFS); detectable end-EBV DNA loads were associated with significantly worse loco-regional recurrence free survival (LRRFS) and PFS, and the detecTable 6 months-post-EBV DNA loads were associated with significantly poorer overall survival (OS), DMFS and PFS (p < 0.05). Additionally, combining the pre-EBV DNA load and the stage of the disease, our results showed that patients at stage III-IVA with a low pre-EBV DNA load had similar survival rates as patients at stage II with a low or high pre-EBV DNA load, but had better survival rates than those at stage III-IVA with a high pre-EBV DNA load. Taken together, we showed that the change of the EBV DNA load measured at several time points was more valuable than at any single time point for predicting patients’ survival for NPC. Furthermore, combining the pre-EBV DNA load and the TNM classification could help to formulate an improved prognostic model for this cancer.