Circulating and tumor-associated neutrophil subtypes discriminate hyperprogressive disease (HPD) from conventional progression (PD) upon immune checkpoint inhibitors (ICI) in advanced non-small cell lung cancer (NSCLC) patients (pts) and in vivo models.

9547 Background: HPD occurs in ≃10-25% of NSCLC pts upon single-agent ICI and correlates with poor prognosis. High circulating neutrophil count and neutrophils/lymphocytes ratio have been associated with shorter survival and HPD in NSCLC pts. In mouse lung cancer models, interleukin-17 (IL-17) promoted tumour growth upon ICI increasing intratumoral neutrophils. The role of specific circulating and/or tumour-associated neutrophils in driving HPD is currently unknown. Methods: NSCLC pts treated with single agent ICI were assessed for HPD and circulating neutrophils’ phenotype. Conventional PD was defined by RECIST 1.1. HPD required 3 tumour assessments (2 before ICI, 1 upon ICI) and was defined as delta tumour growth rate (TGR) (TGR upon ICI – TGR before ICI) > 50% and/or TGR ratio (TGR upon ICI/ TGR before ICI) ≥2. Correlations with continuous variables were performed by Mann-Whitney test. Circulating low density neutrophils (LDNs) subtypes were assessed by flow cytometry (FC) on peripheral blood mononuclear cells (PBMCs) from fresh blood samples. LDNs were defined as CD66b+CD15+ cells among CD11b+ PBMCs. Immature subtypes were defined as CD10− and CD10−CD16− LDNs. The occurrence of HPD upon anti-PD-1 treatment was tested in C57BL/6 immune competent mice bearing Lewis Lung Carcinoma and treated with anti-murine PD-1. Tumour associated neutrophils’ phenotype was assessed by FC. Results: Of 52 NSCLC, 65% were > 65 years, 83% had stage IV, 25% PD-L1 on tumour cells ≥50%, 67% received 1st line ICI. PD and HPD occurred in 21 (40%) and 5 (10%) pts, respectively. Before ICI start, HPD pts had higher circulating immature neutrophils measured as median percentage of CD10− LDNs [41.9 (min 26.7; max 83.5) vs 10.1 (min 0.69; max 79.3), p = 0.01] and of CD16− cells among CD10− LDNs [93 (min 89.5; max 98.4) vs 86.3 (min 24.2; max 99), p = 0.03] compared to conventional PD pts. PD and HPD occurred in 17 (71%) and 3 (12.5%) of 24 immune competent mice treated with anti-murine PD-1. The median percentage of IL-17+ tumour associated neutrophils (Gr1highLy6Clow) was significantly higher in HPD compared to PD mice [0.25 (min 0.14; max 0.63) vs 0.06 (min 0.02; max 0.32), p = 0.02]. Conclusions: Circulating immature (CD10− and CD10− CD16−) LDNs and IL-17+ tumour associated neutrophils discriminate HPD from conventional PD upon ICI in NSCLC pts and in vivo models, respectively. Functional characterization of specific neutrophil subsets is ongoing.