Baseline Neutrophil-to-Eosinophil Ratio Is Associated with Outcomes in Metastatic Renal Cell Carcinoma Treated with Immune Checkpoint Inhibitors

Background Biomarkers have the potential to guide treatment selection and clinical care in metastatic renal cell carcinoma (mRCC) in an expanding treatment landscape. We report baseline neutrophil-to-eosinophil ratios (NER) in patients with mRCC treated with immune checkpoint inhibitors (CPIs) and their association with clinical outcomes. Methods We conducted a retrospective review of patients with mRCC treated with CPIs at Winship Cancer Institute from 2015 to 2020 in the United States of America (USA). Demographics, disease characteristics, and laboratory data, including complete blood counts (CBC) were described at the initiation of CPIs. Clinical outcomes were measured as overall survival (OS), progression-free survival (PFS), and clinical benefit (CB) associated with baseline lab values. Results A total of 184 patients were included with a median follow-up time of 25.4 months. Patients with baseline NER were categorized into high or low subgroups; high group was defined as NER >49.2 and low group was defined as NER <49.2 with 25% of patients in the high NER group. Univariate analyses (UVA) and multivariable analyses (MVA) identified decreased overall survival (OS) associated with elevated NER. In MVA, patients with a high baseline NER group had a hazard ratio (HR) of 1.68 (95%CI, 1.01-2.82, P = .048) for OS; however, there was no significant difference between groups for PFS. Clinical benefit was seen in 47.3% of patients with low baseline NER and 40% with high NER. Conclusions We conclude that elevated baseline NER may be associated with worse clinical outcomes in mRCC. Although results require further validation, NER is a feasible biomarker in patients with CPI-treated mRCC. This article reports on the role of the neutrophil-to-eosinophil ratio as a potential biomarker in metastatic renal cell carcinoma.