Eosinophil Counts: A Potential Biomarker for Predicting Immunotherapy Response in NSCLC?

By: Joshua D. Madera, MD
Posted: Monday, January 6, 2025

For patients with non–small cell lung cancer, the peripheral eosinophil count may be used as a biomarker to determine clinical response to the PD-1 inhibitor nivolumab and overall survival, according to the results of a study published in the American Journal of Cancer Research. Using a diagnostic approach with the eosinophil count and the extent of PD-L1 expression may enable clinicians to improve personalized treatment strategies in this patient population, suggested Sema Sezgin Göksu, MD, of Akdeniz University, Antalya, Turkey, and colleagues. Further validation of these findings is necessary in future multicenter randomized studies with a larger sample size.

“Traditionally known for their role in allergic responses and parasitic infections, eosinophils are gaining attention as mediators in antitumour immunity,” note the investigators.

From 2019 to 2023, a total of 174 patients with metastatic NSCLC were recruited for the study. All patients were previously treated with at least one line of chemotherapy and showed evidence of disease progression. Baseline labs, including eosinophil counts and PD-L1 levels, were performed on all patients before starting therapy with nivolumab. Patients were closely monitored to assess for treatment-related adverse events and to evaluate clinical outcomes.

The study findings demonstrated that patients who had an increased number of peripheral blood eosinophils at baseline had a significant response to nivolumab therapy. These patients also had improved overall survival. In addition, after treatment with nivolumab, the number of patients with eosinophils between 100 and 499 cells/mm³ increased from 54.1% to 70.8%. Furthermore, patients with PD-L1 positivity greater than 50% had significantly improved survival outcomes (mean survival = 24.1 months). These patients had average eosinophil levels of 266 cells/mm³. In contrast, patients who did not respond to treatment had decreased survival outcomes (mean survival = 19.1 months).

Disclosure: The study authors reported no conflicts of interest.

American Journal of Cancer Research