Association between time to treatment failure and peripheral eosinophils in patients with non-small cell lung cancer treated with immune checkpoint inhibitors.

Introduction: There is an unmet clinical need to identify biomarkers predicting which patients with non–small cell lung cancer (NSCLC) would benefit from treatment with immune checkpoint inhibitors (ICPIs). Objectives: The purpose of this study was to draw a detailed time to treatment failure (TTF) curve with information on the changes in peripheral eosinophil expression during ICPI treatment for NSCLC, and to clarify whether eosinophil expression can predict prolonged TTF. Patients and methods: In 259 patients with NSCLC treated with ICPI therapy, peripheral eosinophil counts and percentages at the time of each ICPI administration were evaluated from the beginning of ICPI treatment up to TTF. Univariable and multivariable analyses were performed to identify clinical factors associated with TTF. Results: Patients receiving ICPI monotherapy (n = 180) were divided into 3 groups (TTF ≤6 weeks, TTF >6 weeks and ≤24 weeks, and TTF >24 weeks) and the number of patients with an eosinophil percentage of 5% or more within 6 weeks of ICPI therapy initiation was significantly different among these groups. In univariable and multivariable analyses, performance status of 0 to 1, immune-related adverse event not requiring ICPI discontinuation as well as an eosinophil percentage of 5% or more and an eosinophil count of 330/μ or more within 6 weeks of ICPI therapy initiation were significant favorable factors for prolonged TTF. In patients treated with combination therapy of ICPI and chemotherapy (n = 79), the number of patients with an eosinophil percentage of 5% or more within 12 weeks of therapy initiation was significantly different between patients with a TTF of up to 12 weeks and those with a more prolonged TTF. However, the only significant favorable factor for TTF was female sex. Conclusions: In NSCLC patients treated with ICPI therapy, particularly ICPI monotherapy, eosinophil measurements during treatment might be useful for predicting prolonged TTF.