Plasma EBV DNA have been used in the detection of primary nasopharyngeal carcinoma (NPC) but has not been thoroughly evaluated in the detection of locally recurrent or persistent NPC. Here we sought to evaluate the sensitivity and specificity of plasma EBV DNA in the detection of locally recurrent/ persistent NPC.
Prospective case-control study evaluating patients with biopsy proven NPC and controls with a history of NPC, now proven disease free with clinical examination and MRI. Plasma EBV DNA was performed with a value of 0 being normal. ROC curves were also generated to determine an optimal cutoff. Sensitivity, specificity, positive predictive value and negative predictive values were also determined. SPSS (IBM) was used for statistical analysis.
Forty-nine males and twenty females with an average age of 56.9 (SD +/- 9.7) (range 27 – 79) years old were recruited, comprising 20 recurrence and 49 control cases . Among the locally recurrent group of twenty patients, 8 had T1 disease; 2 had T2 disease; 3 had T3 disease; 4 had T4 disease. The optimal detection level of plasma EBV DNA was 2.0 (AUC = 0.831, p<0.05) for locally recurrent NPC (Figure 1). The sensitivity and specificity of the plasma EBV DNA using any positivity as a positive test result were 70.0% (95% CI 45.72 – 88.11%) and 95.92% (95% 86.02 – 99.5%) respectively. The positive predictive value was 87.5% (95% CI 63.61 – 96.56%) and the negative predictive value was 88.68% (95% CI 80.0 – 93.88%). Using the ROC value the same results were obtained. Moreover, there was a positive correlation between the recurrent T-classification and plasma EBV DNA levels r = 0.554 (p =0.017) (Figure 2).
Plasma EBV DNA is specific but not sensitive in detecting locally recurrent NPC. The level of EBV DNA also correlates with the T classification. The test may provide additional surveillance modalities besides current practice when used in combination for the detection of locally recurrent nasopharyngeal carcinoma. Further study with a larger sample size would be required to validate the use of plasma EBV DNA in local recurrent NPC.