Association of Pretreatment Neutrophil-to-Eosinophil Ratio with Clinical Outcomes in Patients with Recurrent or Metastatic Head and Neck Squamous Cell Carcinoma Treated with Nivolumab

Background: There is a need to develop biomarkers for a more efficient use of immune checkpoint inhibitors (ICIs). Recently, it has been reported that peripheral blood components, including eosinophils, may be effective ICI biomarkers. This study was designed to evaluate the prognostic value of eosinophils for measuring the effects of nivolumab on recurrent/metastatic head and neck squamous cell carcinoma (R/M HNSCC). Materials and Methods: The study included 47 patients with R/M HNSCC treated with nivolumab. Eosinophil-related biomarkers, such as absolute eosinophil count (AEC), relative eosinophil count (REC), and neutrophil-to-eosinophil ratio (NER), were measured from the peripheral blood of the patients before nivolumab treatment. For each biomarker, the patients were divided into a high- and a low-value group according to their cutoff values, and these groups were compared. Results: Regarding AEC and REC, no significant improvement in the objective response rate (ORR) was observed between patients with AEC >0.9 x 1[0.SUP.3]/[MICRO]L and those with AEC 2.2% and those with REC 0.9 x 1[0.sup.3]/[micro]L, REC >2.2%, and NER