Elevated eosinophils proportion as predictor of immune‐related adverse events after ipilimumab and nivolumab treatment of advanced and metastatic renal cell carcinoma.

Objectives: Ipilimumab and nivolumab treatment against advanced and metastatic renal cell carcinoma (RCC) causes severe and lethal immune‐related adverse events (irAEs). Predicting irAEs might improve clinical outcomes, however no practical biomarkers exist. This study examined whether eosinophils could be effective biomarkers for ≥grade 2 irAEs in RCC. Methods: We retrospectively analyzed 75 patients with RCC treated with ipilimumab and nivolumab between August 2018 and March 2021 in a multicenter study. Eosinophils were examined before and 2 weeks after treatment, and immediately after irAEs development. The optimal cut‐off value for ≥grade 2 irAEs was determined by a receiver operating characteristic (ROC) curve. Univariate and multivariate analyses were undertaken to identify predictors of ≥grade 2 irAEs. Results: Two weeks after treatment, eosinophils were significantly upregulated in patients who had experienced ≥grade 2 irAEs than in those who had not experienced irAEs (mean, 5.7% vs. 3.2%; p < 0.05). The optimal cut‐off value for eosinophils against ≥grade 2 irAEs was 3.0% (area under the curve = 0.69). In multivariate analyses, an eosinophil level ≥ 3.0% was a risk factor for ≥grade 2 irAEs (odds ratio 4.18, 95% confidence interval 1.16–15.1). The eosinophil level 2 weeks after treatment was upregulated by the onset of any type of irAEs including endocrine, gastrointestinal, pulmonary and skin disorders. Conclusions: An increased eosinophil level 2 weeks after treatment might be an effective biomarker for ≥grade 2 irAEs in patients with RCC treated with ipilimumab and nivolumab. [ABSTRACT FROM AUTHOR]