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Archive > Volume 33 Issue 3 > 2026,33(3):296-312. DOI:10.3872/j.issn.1007-385X.2026.03.009 Prev Next
Clinical Research
Predictive value of eosinophils in immunotherapy for small cell lung cancer
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Abstract:
[Abstract] Objective: To investigate the predictive value of eosinophils (Eos), other circulating blood cells, and inflammatory markers for the efficacy of immunotherapy and immune-related adverse events (irAEs) in small cell lung cancer (SCLC). Methods: A retrospective analysis was conducted on the clinical information of 410 SCLC patients admitted to the Department of Respiratory and Critical Care Medicine, the First Affiliated Hospital of Second Military Medical University between August 2013 and July 2023. Complete blood cell counts and cytokine levels were measured before chemotherapy/immunotherapy and after three treatment cycles. The onset time, type, grade, and follow-up information of irAEs were recorded. Results: Among the patients, 116 received chemotherapy combined with immune checkpoint inhibitors (ICIs), including 91 with first-line treatment and 25 with later-line treatment. The overall response rate (ORR) was 44.8% and the disease control rate (DCR) was 90.5% in the combination group, compared to 38.4% and 85.0%, respectively, in the chemotherapy-alone group. The median progression-free survival (PFS) was 8.9 (7.2-10.5) months and median overall survival (OS) was 17.7 (13.9-21.5) months in the combination group. After propensity score matching (PSM) between the combination and chemotherapy-alone groups, the levels of absolute eosinophil count (AEC) and relative eosinophil count (REC) after three treatment cycles were compared. Ratios of follow-up Eos levels to baseline levels (AECT1/0, AECT2/0, AECT3/0, RECT1/0, RECT2/0, RECT3/0) were calculated, and the results showed that AECT3/0 and RECT3/0 in the combination group were significantly higher than those in the chemotherapy-alone group. Univariate analysis showed that elevated baseline AEC and REC were significantly associated with better time to treatment failure (TTF) and OS (P < 0.05). The ratio of post-treatment to baseline Eos levels (AECT3/0, RECT3/0) was significantly associated with better PFS and TTF (P < 0.05). Elevated RECT3/0 was also significantly associated with improved OS (P < 0.05). Multivariate analysis indicated that AECT3/0 > 0.41 was significantly associated with better PFS and TTF (P < 0.05), RECT3/0 > 0.32 was significantly associated with better PFS, TTF, and OS (P < 0.05), while RECT3/0 > 0.27 was only significantly associated with better TTF and OS (P < 0.05). Subgroup analysis revealed that RECT3/0 was significantly higher in the response group than in the non-response group (P < 0.05). There was no statistical difference in PFS, TTF, or OS between patients receiving first-line versus second-/later-line ICI therapy. However, ORR (50% vs 25%, P < 0.05) and DCR (93.48% vs 79.17%, P < 0.05) were significantly superior with first-line ICI use. Among the 116 patients in the combination group, 43 (35.34%) experienced irAEs, most commonly immune-related dermatitis (8.62%). Grade Ⅲ or higher irAEs occurred in 17 patients (14.66%), leading to treatment discontinuation in 10 cases (8.62%) and deaths in 2 cases. Patients who experienced irAEs had significantly longer PFS compared to those without irAEs (P < 0.05), while TTF and OS were not significantly different. RECT3 levels were significantly higher in patients with irAEs than in those without (P < 0.05), and AECT3/0 > 0.29 was associated with a significantly higher incidence of irAEs (P < 0.05). Conclusion: Eosinophils represent a protective factor in SCLC patients receiving ICI therapy. Monitoring AECT3/0 and RECT3/0, combined with patient clinicopathological characteristics, cytokines, and inflammatory markers, can effectively predict immunotherapy efficacy and the occurrence of irAEs in SCLC patients.
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