Exploring the Dynamics of Immune Checkpoint Inhibitor‐Induced Eosinophilia in Advanced/Metastatic Melanoma: A Comprehensive Retrospective Analysis

Abstract

ABSTRACT Background Immune‐related eosinophilia has emerged as an adverse event associated with immune checkpoint inhibitors (ICIs). Its prevalence, severity, duration, clinical significance, diagnostic approach, and management remain unexplored. Methods We conducted a retrospective review of melanoma patient records at a university referral center. Our analysis encompassed the incidence of eosinophilia, baseline disease characteristics, treatment modalities, peak eosinophil counts, associated symptoms, diagnostic procedures, management strategies, disease course, and prognostic implications. Results A total of 308 patients were included. Eosinophilia was present in 21.4%, and there was no association with gender, age, histologic type, stage, or BRAF mutation status. The median time interval from treatment initiation to the eosinophilia onset was 56 days, the median eosinophil count at first presentation was 0.70 × 109/L, and the maximum eosinophil count was 1.02 × 109/L. The rate of eosinophilia was significantly higher in patients treated with nivolumab plus bempegaldesleukin (50.0%), followed by nivolumab plus ipilimumab (21.7%). Symptomatic patients and/or patients with hypereosinophilia were assessed for organ involvement and for the identification of the cause of eosinophilia. Patients requiring medical intervention were managed with corticosteroids or antihistamines. Eosinophilia relapsed in 31.8% when rechallenged. While non‐significant, there was a numeric trend for longer overall survival in patients with eosinophilia (42.6 vs. 27.9 months, p = 0.178). Conclusions This study marks the first comprehensive approach of the relationship between the type of immunotherapy and the incidence of eosinophilia in melanoma patients. It also delves into the patients' baseline characteristics, diagnostic assessment, management, and prognosis, providing useful guidance for physicians treating patients with ICIs.

Keywords

• eosinophilia
• immune check point inhibitors
• immune related adverse events
• immunotherapy
• melanoma