ObjectiveTo explore the application value of plasma Epstein-Barr virus (EBV) DNA test in the clinical diagnosis of patients with nasopharyngeal carcinoma in non-high-incidence areas of Southwest China and its significance for monitoring patients after treatment. MethodsA total of 235 patients diagnosed with non-keratinized nasopharyngeal carcinoma between January 2014 and December 2015 were retrospectively collected. The plasma EBV-DNA test rate of the nasopharyngeal carcinoma patients before treatment, the positive rates of the plasma EBV-DNA test before treatment and within 6 months of treatment, and the relationship between the positivity of plasma EBV-DNA within 6 months of treatment and the prognosis of nasopharyngeal carcinoma were analyzed. ResultsThe plasma EBV-DNA test rate of the nasopharyngeal carcinoma patients before treatment was 69.79% (164/235), with a positive rate of 90.85% (149/164). A total of 131 patients were tested for EBV-DNA within 6 months of treatment, whose positive rate was 89.31% (117/131) before treatment and 21.37% (28/131) within 6 months of treatment, respectively, with a statistically significant difference (P<0.001). Comparing the prognosis of EBV-DNA positive patients and negative patients within 6 months of treatment, the difference in 3-year recurrence rate between the two groups was not statistically significant (10.71% vs. 3.88%, P=0.341); however, the 3-year metastasis rate (21.43% vs. 4.85%, P=0.016) and the 3-year disease progression rate (32.14% vs. 6.80%, P=0.001) of the EBV-DNA positive patients were higher than those of the EBV-DNA negative patients, and the log-rank test slao showed that the 3-year progression-free survival rate (67.86% vs. 93.20%, P<0.001) and the 3-year metastasis-free survival rate (78.57% vs. 95.15%, P=0.004) of the EBV-DNA positive patients were lower than those of the EBV-DNA negative patients. There was no statistically significant between-group difference in the 3-year progression-free survival curve when grouped by age, gender, or TNM staging (P>0.05).ConclusionsFor patients with non-keratinized nasopharyngeal carcinoma in non-high-incidence areas of Southwest China, EBV-DNA detection is important for the screening and diagnosis of nasopharyngeal carcinoma, and the positivity of EBV-DNA test within half a year of treatment is an important factor affecting the prognosis and progression of patients. Plasma EBV-DNA levels should be monitored regularly before and after treatment.