4P - Assessment of PD-L1 expression by immunohistochemistry in histological and cytological non-small cell lung carcinoma (NSCLC) in the era of immunotherapy: A national Irish study
- Aurelie Fabre (IE)
- Katie Breen (IE)
- Janet McCormack (IE)
- Aurelie Fabre (IE)
Abstract
Background
Evasion of immune system is a hallmark of cancer, which enables cancer cells to escape the attack from immune cells, by expression of immune inhibitory signalling proteins such as programmed death-ligand-1 (PD-L1); PD-L1 binds to programmed death-1 (PD-1) expressed on immune cells (T, B, dendritic and NK T-cells) to suppress anti-cancer immunity. Anti PD-L1antibodies (such as pembrolizumab) are now being used for the treatment of some cancers.
Methods
We assessed the expression of PD-L1 on NSCLC by immunohistochemistry using the Dako IHC22C3 pharmDx® kit on the Dako Autostainer link48®. Slides were read and scored using the Dako guidelines based on a Tumour Proportion Score (TPS) (% of tumour cells expressing PD-L1, ≤1% (negative), 1–49% (low), ≥50% (positive)). Immune cells were not scored.
Results
The 16 months-patient cohort was made up of 870 patients, from SVUH (43.9%) and Irish national hospitals (61.2%), 49.5% females and 51.5% males. Overall staining patterns were as follows: 31.5% positive (high TPS >50%), 23.1% low (low TPS 1–49%), 42.8% negative (TPS <1%). Specimens included cytology (22.9%, of which 57% were EBUS samples), biopsy (77.1%, 39% were lung/bronchial biopsies) and surgical (15.6%) specimens. Adenocarcinomas represented 59.3% of all NSCLC and 33.5% had a high TPS (≥50%) score. Squamous cell carcinomas (33.7%) were positive (≥50%) in 29.7%. Histology and cytology samples had similar distribution of high, low and negative TPS cases.
Conclusions
This is the first comprehensive collection of PD-L1 testing data in NSCLC in Ireland. Our results broadly with the KEYNOTE-010 study validating our scoring. Some of these patients are now receiving pembrolizumab treatment. Heterogenous tumour populations and strong staining of inflammatory cells can make assessment difficult.
Legal entity responsible for the study
St. Vincent's University Hospital Dublin
Funding
MSD
Disclosure
A. Fabre, K. Breen, J. McCormack: Financial funding received from MSD.
