Background and objectives: Recent studies show that interleukin-6 (IL-6) plays a role in tumor development and expansion. However, available information related to the prognostic significance of IL-6 for oral squamous cell carcinoma (OSCC) is limited. This study aimed to determine the role of serum IL-6 concentration in early stage OSCC patients defined by sentinel node biopsy (SNB). SNB is a minimally invasive and highly reliable staging method of the cN0 neck.
Methods: Forty-two patients with cT1-2N0 OSCC underwent SNB between 2006 and 2012. Sentinel lymph node was determined by radioisotope method, and evaluated by histopathological examination and genetic analysis. We measured the levels of IL-6 in the sera taken from these patients by using ELISA. Results were correlated with disease-free survival (DFS) including second primary cancer. For statistical analysis, the Log-rank test was performed. Values of P < 0.05 were considered statistically significant.
Results: Cut-off of serum IL-6 value was decided to be 20 pg/ml based on ROC curve. In 42 cStage I/II patients before SNB, DFS of the patients with low IL6 tended to be longer than that of the high IL-6 patients although there was no significant difference ( P = 0.07). SNB showed pN1(Sn) in 7 of 42 patients (16.7%) and excluded 5 patients (11.9%) as these are reclassified to pT4 from the surgically resected specimen. Thus, 33 patients were defined as early stage OSCC. In these 33 patients, DFS of the IL6lo patients was statistically significantly longer than that of IL6hi patients (P = 0.02). Especially, in 26 patients who have been observed at least for 2 years, the disease free rate of IL-6lo patients was 100%.
Conclusions: These findings strongly suggest that the staging of SNB and preoperative serum IL-6 level have a high prognostic value in OSCC patients.