BASELINE EOSINOPHIL LEVELS and early changes in simple blood-based immune markers may help predict treatment outcomes in patients with metastatic renal cell carcinoma (mRCC) receiving nivolumab, according to new research. The findings suggest that routinely available laboratory parameters could offer clinicians an accessible way to identify patients most likely to benefit from immune checkpoint inhibitor therapy.
Immune checkpoint inhibitors, including the PD-1 inhibitor nivolumab, have transformed the treatment landscape for mRCC. However, patient responses vary, and there is an ongoing need for reliable biomarkers that can predict survival and treatment response. Increasing attention has focused on eosinophils, immune cells thought to play a role in modulating anti-tumour immune responses.
Neutrophil-to-Eosinophil Ratio Emerges as a Prognostic Tool
In this large retrospective analysis, researchers evaluated 458 patients with mRCC treated with nivolumab. They studied absolute eosinophil count (AEC) and the neutrophil-to-eosinophil ratio (NER) at baseline and one month after treatment initiation, as well as early changes in these parameters. The study assessed associations with progression-free survival (PFS), overall survival (OS), and objective response rate (ORR).
Patients with a baseline AEC of at least 70 cells/µL experienced significantly better outcomes, including longer PFS and OS, compared with those with lower eosinophil counts. Similar benefits were observed when AEC remained at or above this threshold one month after starting nivolumab. A lower NER, particularly below 65 one month into treatment, was also strongly associated with improved survival outcomes. Baseline NER below this level predicted superior overall survival.
Early changes in these markers were also clinically relevant. A marked increase in NER (≥125%) after one month of therapy was linked to worse PFS and OS, while a substantial drop in eosinophil count (greater than 30%) was associated with poorer overall survival. In contrast, patients with favourable baseline and early-treatment eosinophil profiles were more likely to achieve an objective tumour response.
Routine Blood Counts Could Guide Immunotherapy Decisions
Importantly, these biomarkers are inexpensive, widely available, and derived from standard blood counts, making them accessible for routine clinical use. The authors conclude that eosinophil-based parameters, including AEC and NER, along with their early dynamics during nivolumab therapy, show promise as prognostic tools in mRCC.
While the findings require prospective validation, they highlight the potential role of simple immune markers in guiding treatment decisions and improving personalised care for patients with advanced kidney cancer.
Reference
Fiala O et al. Baseline and early changes in eosinophil count and neutrophil-to-eosinophil ratio predict outcomes in metastatic renal cell carcinoma treated with nivolumab. Sci Rep. 2025;doi: 10.1038/s41598-025-32593-8
