Concordance of PD-L1 expression detection in non-small cell lung cancer (NSCLC) tissue biopsies between OncoTect iO single cell PD-L1 quantification assay and immunohistochemistry (IHC).

Abstract

e23172 Background: PD-1/PD-L1 therapy has been shown to be effective in patients with NSCLC, specifically those with 50% PD-L1 expression or greater by IHC. Response rates for those with lower PD-L1 expression do not consistently correlate with PD-L1 amount. The OncoTect iO Lung PD-L1 Assay was designed to provide non-subjective quantification of PD-L1 expression on tumor cells and immune cells from a multitude of tumor types. The objective of this study was to compare OncoTect iO and the current method of PD-L1 testing by immunohistochemistry (IHC) in NSCLC biopsies. Methods: Eleven NSCLC tissues were obtained from two IRB approved sites. Fresh tissues were processed into single cell suspensions using the IVD IncellPREP Kit (IncellDx, Inc). Normal lung tissue adjacent to tumor sites was obtained for 9 of the samples. Cell suspensions were tested with the OncoTect iO Lung Assay which contains antibodies directed against PD-L1 (28-8), CD45, CD3, and CD8. Suspensions are fixed and permeabilized, labeled with the antibodies, and then stained with DAPI to identify intact, single cells, and to analyze cell cycle including aneuploidy.Matched FFPE sections were taken from the tissue biopsies and were tested at BioReference Laboratories with the Dako PD-L1 IHC 28-8 PharmDx Kit. Results: A cut-off of 4% was used for the OncoTect iO Assay and a positive result for the Dako assay is ≥ 5% of the tumor cells (equivalent to 5 cells out of 100). PD-L1 expression ranged from 0% to 75% in the tumor samples which is consistent with reported ranges. Seven samples were positive by OncoTect iO Lung and 6 were positive by IHC. Twelve samples were negative by OncoTect iO Lung and 13 were negative by IHC demonstrating a concordance of 95%. Of note, one tumor that was negative by OncoTect iO and IHC demonstrated 5% of aneuploidy tumor cells that were positive and most likely very rare to be detected in the assays. Conclusions: In this study, the concordance between Oncotect iO and IHC was 95%, however, the Oncotect iO Single Cell PD-L1 Quantification Assay was fast ( < 3 hours), non-subjective, and provided addition expression information for aneuploid tumor cells.