PD-L1 assessment in cytology samples predicts treatment response to checkpoint inhibitors in NSCLC

• Published in: Lung cancer (Amsterdam, Netherlands) Netherlands), 2022-09, Vol.171, p.42-46
• Main Authors: Lau, Sally C.M., Rabindranath, Madhumitha, Weiss, Jessica, Li, Janice J.N., Fung, Andrea S., Mullen, Dorinda, Alshamlan, Najd, Ruff, Heather M., Tong, Leung Chu B., Pal, Prodipto, Cabanero, Michael R., Hsu, Ying-Han R., Sacher, Adrian G., Shepherd, Frances A., Liu, Geoffrey, Bradbury, Penelope A., Yasufuku, Kazuhiro, Czarnecka-Kujawa, Katarzyna, Mi Ko, Hyang, Tsao, Ming-Sound, Leighl, Natasha B., Schwock, Joerg
• Format: Article
• Language: English
• Subjects: Cytology; Immune checkpoint inhibitors; Immunohistochemistry; Non-small cell lung cancer; PD-L1 testing
• ISSN: 0169-5002; 1872-8332
• DOI: 10.1016/j.lungcan.2022.07.018

•In a large population, cytology and histology samples had similar PD-L1 TPS distribution.•Despite different sites of sampling, overall PD-L1 TPS proportions remained similar.•PD-L1 TPS determined by the 22C3 assay on cytology was predictive of treatment response.•PFS to PD1 inhibitors were similar according to PD-L1 TPS on cytology vs histology samples.•PFS of patients with PD-L1 ≥ 50 % on cytology was comparable to clinical trials. Testing for tumor programmed death ligand-1 (PD-L1) expression was initially developed with histology specimens in non-small cell lung cancer (NSCLC). However, cytology specimens are widely used for primary diagnosis and biomarker studies in clinical practice. Limited clinical data exist on the predictiveness of cytology-derived PD-L1 scores for response to immune checkpoint inhibitor (ICI) therapy. We reviewed all NSCLC specimens clinically tested at the University Health Network (UHN) for PD-L1 with 22C3pharmDx, from 01/2013 to 04/2021. Treatment outcomes in patients treated with single agent ICI therapy were reviewed and compared according to cytology- and histology-derived PD-L1 scores. We identified 494 and 1942 unique patients with cytology- and histology-derived tumor proportion scores, respectively, during the study period. Informative testing rates were 95 % vs 98 % for cytology and histology, respectively. Clinical data were available for 152 patients treated with single agent ICI: 61 cytology and 91 histology. Overall response rates (ORR) were similar for cytology and histology (36 % vs 34 %; p = 0.23), as well as median progression free survival (PFS) (4.9 vs 4.2 months; p = 0.99) and overall survival (23.4 vs 19.7 months; p = 0.99). The results remained similar even after adjusting for PD-L1 expression levels and line of ICI treatment (PFS HR 1.15; 95 %CI 0.78–1.70; p = 0.47). Treatment outcomes to single agent ICI based on cytology-derived PD-L1 scores were comparable to histology controls. Our results support PD-L1 biomarker testing on both cytology and histology specimens.