398PD PD-L1 status in Taiwanese lung adenocarcinoma patients: Comparison of PD-L1 immunohistochemical assays using antibody clones 22C3, SP142 and SP263 with clinicopathological correlation

Abstract

Background In non-small cell lung cancer, immune checkpoint blockade of PD-1 axis had shown promising treatment results. There are at least four different PD-1 axis blocking agents and each was accompanied by its own PD-L1 IHC assay as a biomarker test. Data are still limited regarding the comparison between different assays. The aim of this study is to compare the staining characteristics of different PD-L1 IHC assays and correlate the results with clinical, pathological and molecular features in a large cohort of lung adenocarcinoma patients in Taiwan. Methods This study used a tissue microarray constructed with tumor tissue from 219 lung adenocarcinoma patients who underwent surgical resection in Taipei Veterans General Hospital. Three different PD-L1 IHC assays were performed: Dako 22C3 pharmDx on Dako autostainer, SP142 (Spring Bioscience) on Leica autostainer, SP263 (Ventana) on Ventana autostainer. Positive PD-L1 expression was defined as membranous staining in > 1% of tumor cells; negative PD-L1 expression was defined as membranousstainingin<1%tumorcells.CorrelationsbetweendifferentPD-L1assays and clinicopathological features were investigated. Results:PD-L1 positiverateswere16.9%,15.5%and40.6%with22C3,SP142and SP263,respectively. PD-L1 expression wasconcordantin 158patients (72.1%),among whom129(58.9%)werePD-L1 negative,and29(13.2%)werePD-L1 positivewithall assays. Therewasahigh concordancebetween22C3 andSP142(94%).SP263 showed lower concordance with the other two assays (76.3% and 74% concordance with 22C3 andSP142,respectively).Inallassays,solidhistologywasassociatedwithhigherrateof PD-L1positivity(P<0.001),andEGFRmutationwasnegativelycorrelatedwithPD-L1 expression(P<0.05).PD-L1 positivitywasassociatedwithpoorsurvival(P<0.001). Conclusions:PD-L1 IHCassayswith22C3andSP142showedhighconcordance,but SP263assayshowedsubstantialhigherrateofPD-L1 positivity.Theassociations betweenPD-L1 expressionandclinicopathologicalfeatures,includingtumorhistology, EGFR mutation and survival, were consistent across different PD-L1 IHC assays. Legal entity responsible for the study Taipei Veterans General Hospital Funding Taipei Veterans General Hospital Disclosure All authors have declared no conflicts of interest.