Abstract 319P
Background
Prognosis of patients (p) with extensive-stage small-cell lung cancer (ES-SCLC) remains poor, even with first-line anti-PD-L1 therapy plus platinum and etoposide. Tumor PD-L1 expression by IHC does not discriminate p who benefit most. The expression of PD-L1 on the surface of circulation cells may impact therapy efficacy. Our objetive was to determine basal PD-L1 expression on leukocyte subpopulations in ES-SCLC p and to compare these levels to those in healthy donors (HD).
Methods
Basal blood samples were collected from 46 ES-SCLC. All p received first-line atezolizumab - platinum - etoposide. Lymphocytes were gated according to size and complexity. Samples were analyzed by flow cytometry. PD-L1 expression levels on leukocyte subpopulations were compared between ES-SCLC p and HD (N=15). Descriptive statistics were used to report baseline characteristics. Kaplan-Meier was used to estimate survival rates.
Results
Median age was 69 years; 65.2% p were male, ECOG-PS in p was 0 in 21.7%, 1 in 76.1%, 2 in 2.2%. Median follow-up was 9.02 months (IQR 31.68), with 13 patients (28.3%) alive at data cut-off (Sept. 2024). 14 patients (30%) experienced immune-related adverse events. Median PFS was 6.65 months (95% CI 5.85–7.44) and median OS was 11.71 months (95% CI 8.84–14.58). Flow cytometry results revealed higher percentages of PD-L1+ CD4+ T lymphocytes (p=0.03), PD-L1+ CD8+ T lymphocytes (p < 0.001), PD-L1+ B cells (p=0.03), PD-L1+ neutrophils (p=0.006) and PD-L1+ monocytes (p=0.006) in ES-SCLC p vs. HD. PDL1+ natural killer cells trended higher in ES-SCLC patients vs. HD, without reaching statistical significance (p=0.06).
Conclusions
Patients with ES-SCLC showed higher percentages of circulating PD-L1+ CD4+/CD8+ T lymphocytes, PD-L1+ B cells, PD-L1+ neutrophils, and PD-L1+ monocytes at baseline than HD. These differences could support future research into new biomarkers.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
S. Martinez Recio: Financial Interests, Personal, Invited Speaker: Pierre Fabre, Sanofi, BMS, Takeda; Other, Personal, Other, Meeting registration expenses, travel fees: Merck; Other, Personal, Other, Accommodation expenses: Sanofi; Other, Personal, Other, Travel fees: Lilly; Other, Personal, Other, Meeting registration expenses: BMS, Pfizer, Roche; Other, Personal, Other, Meeting registration expenses, travel fees, accommodation expenses: Novartis. A. Barba Joaquín: Financial Interests, Personal, Invited Speaker: Pfizer, MSD, Sanofi, BMS, Novartis, Roche, AstraZeneca, Pierre Fabre; Financial Interests, Personal, Expert Testimony: BMS; Financial Interests, Personal, Advisory Board: Sanofi, Roche, AstraZeneca; Financial Interests, Personal, Other, congress funding: Janssen, Pfizer, Roche, Pierre Fabre; Non-Financial Interests, Personal, Principal Investigator, PI - Clinical Trial C4221016: Pfizer; Non-Financial Interests, Personal, Principal Investigator, Clinical Trial CA224-1044: BMS; Non-Financial Interests, Personal, Principal Investigator, DZ2022E0005 & DZ2019E0001: Dizal. I.G. Sullivan: Financial Interests, Personal, Advisory Board: Roche, Takeda, Sanofi, Bristol Myers Squibb; Financial Interests, Personal, Invited Speaker: Roche, AstraZeneca, Takeda. M. Majem: Financial Interests, Personal, Advisory Board: Amgen, Roche, AstraZeneca, Takeda, Janssen, Casen Recordati, BMS, Sanofi, Pfizer; Financial Interests, Personal, Invited Speaker: Amgen, Roche, AstraZeneca, Pfizer, Takeda, Helsinn, Casen Recordati; Financial Interests, Institutional, Funding: BMS, AstraZeneca, Roche; Non-Financial Interests, Personal, Leadership Role, Board Member: Associacio contra el Cancer Barcelona; Non-Financial Interests, Personal, Leadership Role: Asocacion para la Investigacion del Cancer de Pulmon en Mujeres. All other authors have declared no conflicts of interest.