Baseline and early changes in eosinophil count and neutrophil-to-eosinophil ratio predict outcomes in metastatic renal cell carcinoma treated with nivolumab

The role of eosinophils in patients with cancer receiving systemic therapy based on immune checkpoint inhibitors (ICIs) has become a subject of increasing interest. The aim of the present study was to assess the prognostic role of absolute eosinophil count (AEC) and neutrophil-to-eosinophil ratio (NER) in patients with metastatic renal cell carcinoma (mRCC) receiving nivolumab. The associations of AEC and NER at baseline and their relative changes (Δ) after one month of nivolumab therapy with progression-free survival (PFS), overall survival (OS), and objective response rate (ORR) were analyzed. In total, 458 patients were included. Baseline AEC ≥ 70 cells/µL (PFS: HR: 0.663, p = 0.009; OS: HR: 0.583, p = 0.002), AEC one month after nivolumab initiation ≥ 70 cells/µL (PFS: HR: 0.544, p = 0.001; OS: HR: 0.331, p < 0.001) and NER < 65 one month after nivolumab initiation (PFS: HR: 0.552, p < 0.001; OS: HR: 0.326, p < 0.001) was associated with superior PFS and OS, and baseline NER < 65 was associated with superior OS (HR: 0.664, p = 0.014). Regarding early dynamics, ΔNER ≥ 125% was associated with inferior PFS (HR: 1.950, p = 0.001) and OS (HR: 2.680, p < 0.001), and ΔAEC <-30% was associated with inferior OS (HR: 2.132, p < 0.001). Higher ORR was associated with baseline AEC ≥ 70 cells/µL (p = 0.048), baseline NER < 65 (p = 0.010); and NER one month after nivolumab initiation < 65 (p = 0.025). The results of the present study suggest that eosinophil-based blood parameters including AEC and NER and their early dynamics during the course of treatment with nivolumab are promising and readily available prognostic biomarkers in patients with mRCC.