Pretreatment eosinophil counts as a predictive biomarker in non‐small cell lung cancer patients treated with immune checkpoint inhibitors

Abstract

BackgroundThe peripheral blood eosinophil count prior to treatment has potential as a predictive biomarker for a beneficial clinical response to cancer immunotherapies. Therefore, the present study investigated the impact of the eosinophil count on overall survival (OS) in non‐small cell lung cancer (NSCLC) patients treated with immune checkpoint inhibitors (ICI).MethodsWe retrospectively reviewed all patients diagnosed with NSCLC and treated with ICI monotherapy between March 2016 and August 2021 at National Hospital Organization Kochi Hospital and Tokushima University.ResultsA total of 166 patients were included. Fifty‐five patients had an eosinophil count of less than 100 cells/μL (Eo < 100). Nighty‐eight patients had an eosinophil count of 100 cells/μL or more, but less than 500 cells/μL (100 ≤ Eo < 500). Thirteen patients had an eosinophil count of 500 cells/μL or more (Eo ≥500). The median OS of all lung cancer patients was 476 days. The median OS of lung cancer patients with Eo <100, 100 ≤ Eo <500, and Eo ≥500 was 339, 667, and 143 days, respectively. A Kaplan–Meier univariate analysis showed a significant difference in OS between these three groups (p < 0.001). A Cox proportional regression analysis identified 100 ≤ Eo <500 (p = 0.04), ECOG PS score ≥ 2 (p = 0.02), tumor size ≥5 cm (p = 0.02), and PD‐L1 ≥ 1% (p = 0.01) as independent predictors of OS.ConclusionOS was significantly longer in ICI‐treated NSCLC patients with a pretreatment eosinophil count of 100 ≤ Eo <500 than in the other patients and, thus, has potential as a new predictive biomarker.

An increased relative eosinophil count as a predictive dynamic biomarker in non‐small cell lung cancer patients treated with immune checkpoint inhibitors

“…Except for an increased REC, these results are consistent with previous findings. 1 , 12 , 22 , 23 In previous studies, the median time to the maximum eosinophil percentage was 5 weeks in lung cancer patients with controlled disease and 2 weeks in those with advanced disease. 15 Under normal conditions, eosinophil production is tightly regulated by the cytokine network.…”

“…Except for an increased REC, these results are consistent with previous findings. 1,12,22,23 In previous studies, the median time to the maximum eosinophil percentage was 5 weeks in lung cancer patients with controlled disease and 2 weeks in those with advanced disease. 15 Under normal conditions, T A B L E 3 Univariate Cox regression analysis of clinical and laboratory parameters associated with the overall survival of non-small cell lung cancer patients treated with immune checkpoint inhibitors.…”

“…We demonstrated the importance of pretreatment eosinophil counts and early mortality factors in ICI monotherapy for advanced or metastatic NSCLC. 12 , 21 The same population was examined as that in our previous study. However, previous research identified early mortality factors and the importance of pretreatment eosinophil counts during ICI treatment.…”

“…According to previous studies, median baseline CRP and Alb levels were selected as cutoff values, 21 while 100 ≤ Eo < 500, sNLR < 5, and tumor size <5 cm were chosen as cutoff values. 12 , 22 , 23 Categorical and continuous variables are summarized using descriptive statistics. The independent samples t ‐test and paired t ‐test were used to analyze differences between continuous variables.…”

“… 11 Overall survival (OS) was longer in ICI‐treated NSCLC patients with a pretreatment eosinophil count of 100 cells/μL or higher, but less than 500 cells/μL (100 ≤ Eo < 500) than in the other patients examined. 12 Meta‐analyses revealed that tumor‐associated tissue eosinophils predicted favorable clinical outcomes in solid tumors. 13 An increased relative eosinophil count (REC) at 3 weeks was identified as a significant predictive factor in urothelial carcinoma patients treated with pembrolizumab.…”