Evaluation of serum interleukin-6 level as a screening/diagnostic marker for patients with nasopharyngeal carcinoma: a comparative study versus Epstein - Barr virus plasma load estimation

ABSTRACT

The present study was designed to evaluate serum levels of interleukin-6 [IL-6] in pre-treatment samples obtained from patients with biopsy confirmed nasopharyngeal carcinoma [NPC] and to correlate it with Epstein-Barr [EBV] DNA plasma load estimated using quantitative PCR, tumor clinical staging and pathological grading so as to determine its applicability as a screening and/or diagnostic marker for NPC. The study comprised 30 patients had biopsy confirmed NPC and 10 healthy volunteers as control for estimated serum IL-6. Patients were subjected to full history taking, complete clinical examination, nasopharyngoscopy and imaging studies. Blood samples were collected prior to and after completion of chemo-radiotherapy course for qualitative identification and quantitative estimation of EBV DNA plasma load and, estimation of serum IL-6. Ten patients were clinically staged II, 12 patients had stage III lesions and 8 patients had stage IV lesions. Histopathologically, 14 specimens were of WHO type 1, 10 specimens of WHO type 2 and 6 specimens WHO type 3. Qualitative PCR could detect EPV-DNA, in all blood samples and mean pre-treatment EBV DNA plasma load was 2126.2 +/- 665; range 1098-3248 copies/ml. The mean pre-treatment serum IL-6 was 175.6 +/- 32.8; range 128-235 ng/ml and was significantly higher than control levels. Mean serum IL-6 was significantly higher in patients clinically staged IV compared to those staged II and III and was significantly higher in patients with lesions type 3 compared to those with lesions type 1 and 2. Mean EBV DNA plasma load was significantly higher in patients staged IV compared to those staged II and III but showed non-significant difference between pathological types. There was a positive significant correlation between estimated serum IL-6 levels and EBV DNA plasma load, [r=0.428, p=0.018], TNM clinical staging of the lesion, [r=0.432, p=0.017] and WHO pathological type, [r=0.513, p=0.004] and between estimated EBV DNA plasma load and TNM clinical staging of the lesion, [r=0.604, p=0.026], but the correlation was non-significant [r=0.344, p>0.05] with WHO pathological type. Evaluation of the specificity of both serum IL-6 and EBV DNA load as a predictor for pathological grade using the receiver operating characteristic [ROC] curve analysis judged by the area under the curve [AUC] revealed a non-significant difference in the specificity of both parameters for prediction of pathological grade of lesion. Post-treatment mean serum level of IL-6 and EBV DNA plasma load were significantly lower compared to pre-treatment level. In conclusion, estimation of serum IL-6 could be used as a screening test for detection of cases of NPC among suspicious patients and as a diagnostic test for cases with established NPC