A harmonization study for the use of 22C3 PD-L1 immunohistochemical staining on ventana's platform

Introduction: Immunotherapy is a novel treatment for lung cancer. Pembrolizumab (Merck Sharp and Dohme, Kenilworth, NJ) is a monoclonal antibody against programmed cell death 1 that has been approved for use with NSCLC together with a companion diagnostic by Dako (Carpinteria, CA). Ventana's BenchMark XT (Ventana Medical Systems, Tucson, AZ) is a widely used immunohistochemical (IHC) platform. However, data on its reliability and reproducibility with the 22C3 antibody are scant. Methods: We performed a comprehensive calibration of 22C3 programmed cell death ligand 1 (PD-L1) staining on the BenchMark XT platform using Dako's prediluted 22C3 anti-PD-L1 primary antibody with two of Ventana's detection systems. Forty-one random cases of NSCLC were then independently evaluated by two pathologists. Each case was scored using Dako-or Ventana-stained slides. The scores obtained with the two 22C3 Ventana assays were compared with those obtained using the Dako 22C3 IHC platform. Results: The Dako IHC platform stratified eight, seven, and 26 cases as being strongly positive, weakly positive, and negative for PD-L1, respectively, whereas 36 of 41 cases (87.8%) had the same results with Ventana's UltraView 22C3 protocol (Pearson's correlation score 0.91, p < 0.0001). Moreover, 35 of 41 cases (85.3%) had the same results with Ventana's OptiView 22C3 protocol (Pearson's correlation score 0.89, p < 0.0001). Conclusions: The results of this study demonstrate that the same PD-L1 IHC algorithm can be reliably applied toVentana's BenchMark XT platform. Furthermore, we were able to detect all of the strongly positive cases with high interobserver and intraobserveragreementbyusingtheVentanaplatform.These findings suggest that the Ventana platform can be used to stratify patients for pembrolizumab-based immunotherapy.