To investigate the changes and clinical significance of Epstein-Barr virus DNA(EB-DNA) in peripheral blood mononuclear cells in patients with nasopharyngeal carcinoma.

Two hundred and twenty cases of nasopharyngeal carcinoma (NPC) diagnosed by pathology at the out-patient and inpatient department of the First Affiliated Hospital of University of Science and Technology of China during April 2014 and October 2017 were enrolled in this study. These patients were aged between 12 and 80 and were divided into 6 groups according to the interval of 10 years of age between ≥71 and ≤ 30 years of age. Real-time fluorescence quantitative polymerase chain reaction (RT-PCR) was used to quantify the EB-DNA loads in peripheral blood mononuclear cells of patients with nasopharyngeal carcinoma. Correlation between EB-DNA load and clinicopathological parameters including gender, age, pathological type and clinical stage was studied. The EB-DNA loads in 82 patients with NPC before and after radiotherapy were followed up for more than 2 years in order to evaluate the relationship between the EB-DNA load change and the recurrence and metastasis of the patients with NPC.

The positive rate of EB-DNA in peripheral blood mononuclear cells in 220 cases of nasopharyngeal carcinoma was 41.4% (91/220); and the average EB-DNA load was 0.0(0.0~612.5) copies/ml. The positive rates and EB-DNA loads had no significant difference between male and female [42% vs. 40%; 0.0(0.0-568.0) copies/ml vs. 0.0(0.0-899.5) copies/ml] and pathological types (χ²=0.079, Z=-0.106; χ²=0.024, Z=-1.182; P>0.05). The positive rate of EB-DNA increased with age (the positive rates of EB-DNA in the 6 groups were 23.1%, 47.1%, 38.6%, 36.8%, 52.9% and 63.6%, respectively) and clinical stage (27.4% in TNM stage II+ III, 45.7% in IV a, and 75.0% in IV b, χ²=3.683, P=0.031; χ²=16.996, P<0.001). In 82 cases of NPC, EB-DNA loads in 57 patients were significantly lower than that before treatment [0.0(0.0~0.0) copies/ml vs. 1390.0(550.0~6535.0) copies/ml; Z=-5.997, P<0.001]. However, in the other 25 patients, the EB-DNA loads were higher than that before treatment [1490.0(348.5~3965.0) copies/ml vs. 0.0(0.0~205.0) copies/ml, Z=-4.529, P<0.001] and significantly difference of EB-DNA loads between the two groups after treatment were found (Z=-6.911, P<0.001). Eighteen of the 25 patients had local recurrence or distant metastasis after treatment.

The positive rate of EB-DNA in peripheral blood mononuclear cells of patients with nasopharyngeal carcinoma increased with age and clinical stage. Regular monitoring of EB-DNA loads after treatment has certain clinical value for prognosis.