Comparison of PD-L1 Expression Using 2 Validated PD-L1 IHC 22C3 pharmDx Methods in Non-Small Cell Lung Cancer in a Routine Hospital Setting

Concordance between 3 validated, commercial programmed cell death ligand 1 (PD-L1) assays and their associated platforms (PD-L1 IHC 22C3 pharmDx Autostainer Link 48, PD-L1 IHC 28-8 pharmDx Autostainer Link 48, and Ventana SP263) has been demonstrated in non-small cell lung cancer. No comparison studies exist for IHC 22C3 pharmDx on the Dako Omnis platform. PD-L1 scoring can be challenging and time-consuming, but no quantitative data exist. A total of 144 formalin-fixed, paraffin-embedded samples from a routine clinical setting were stained with PD-L1 IHC 22C3 pharmDx on the Autostainer Link 48 and on the Dako Omnis platform. Cytologic and histologic material was assessed by 1 pathologist to evaluate the analytical agreement. The ease of PD-L1 scoring was also evaluated. High agreement of PD-L1 scores was found between PD-L1 IHC 22C3 pharmDx on the Autostainer Link 48 and the Dako Omnis platform, whether applied to histologic or cytologic cell blocks, with an overall agreement of 99% and positive agreement and negative agreement of 95%. An overall 76% of the samples that were difficult to score were in the 1% to 49% Tumor Proportion Score category, with no difference between the platforms. Assessment of PD-L1 expression in non-small cell lung cancer, as measured by PD-L1 IHC 22C3 pharmDx on the Autostainer Link 48 and Dako Omnis platform, is feasible on histologic and cytologic specimens. The very high overall agreement, positive agreement, and negative agreement between the 2 PD-L1 staining platforms was demonstrated. Scoring of samples in the Tumor Proportion Score category 1% to 49% was the most difficult and time-consuming.