Neutrophil‐to‐eosinophil ratio as a biomarker for clinical outcomes in advanced stage melanoma patients treated with anti‐PD‐1 therapy

Abstract Neutrophil‐to‐lymphocyte ratios (NLR) and eosinophil counts are associated with improved survival in melanoma patients treated with immune checkpoint inhibitors, but no study has investigated neutrophil‐to‐eosinophil ratios (NER) as a predictive indicator in this population. In this retrospective study evaluating anti‐PD‐1 treated patients with advanced melanoma, progression‐free survival (PFS), overall survival (OS), objective response rates (ORR), and risk of high‐grade (grade ≥3) immune‐related adverse events (irAEs) were compared between groups defined by median pretreatment NLR and NER as well as median NLR and NER at 1‐month post‐treatment. Lower baseline NLR and NER were associated with improved OS [HR: 0.504, 95% CI: 0.328–0.773, p = .002 and HR: 0.442, 95% CI: 0.288–0.681, p < .001, respectively] on univariate testing. After accounting for multiple covariates, our multivariate analysis found that lower pretreatment NER was associated with better ORR (by irRECIST) (OR: 2.199, 95% CI: 1.071–4.582, p = .033) and improved OS (HR: 0.480, 95% CI: 0.296–0.777, p = .003). Baseline NLR, 1‐month NLR, and 1‐month NER were not associated with ORR, PFS, or OS outcomes; but 1‐month NER correlated with lower risk of grade ≥3 irAEs (OR: 0.392, 95% CI: 0.165–0.895, p = .029). Our findings suggest baseline NER merits additional investigation as a novel prognostic marker for advanced melanoma patients receiving anti‐PD‐1‐based regimens.