Salivary Interleukin-6 and-8 in Patients With Oral Cancer and Patients With Chronic Oral Inflammatory Diseases

Background: Previous research has indicated that salivary interleukin (IL)-6 and IL-8 are potential biomarkers for oral squamous cell carcinoma (OSCC). However, their levels have been found to be significantly elevated in patients with chronic periodontitis (CP) or oral lichen planus (OLP). The data also showed wide variations in levels among the different studies, and no standardization procedure was ever performed. Therefore, the objective of this study is to determine whether CP or OLP confounds the use of IL-6 or IL-8 for OSCC detection. Methods: Saliva samples were collected from five groups: OSCC before treatment (n = 18); CP (n = 21); disease-active OLP (n = 21); disease-inactive OLP (n = 20); and healthy controls (n = 21). IL-6 and IL-8 concentrations (determined by enzyme-linked immunosorbent assays) were compared, using total salivary protein-standardized levels to validate the data. The Kruskal-Wallis test (alpha = 0.05) followed by pairwise Mann-Whitney U (post hoc) tests with Bonferroni adjustments (alpha = 0.00625) were used for statistical analysis. Results: Salivary IL-6 levels were significantly higher in patients with OSCC than in patients with CP (P < 0.001), disease-active OLP (P = 0.001), disease-inactive OLP (P < 0.001), and healthy controls (P < 0.001). Salivary IL-8 levels were significantly higher in patients with OSCC than in patients with CP (P < 0.001), but only marginally significantly higher than in healthy controls (P = 0.014). Statistical results of standardized IL-6 and IL-8 levels were consistent with the non-standardized levels in all pairs except one. Conclusion: Salivary IL-6 may be a useful biomarker in the detection of OSCC, unconfounded by CP or OLP.