The Clinicopathological and Molecular Associations of PD-L1 Expression in Non-small Cell Lung Cancer: Analysis of a Series of 10,005 Cases Tested with the 22C3 Assay

PD-L1 expression testing is mandatory prior to pembrolizumab prescription in non-small cell lung cancer. Our service offers PD-L1 testing using the PD-L1 IHC 22C3 pharmDx assay, in parallel with EGFR, ALK, ROS1 and (in some cases) KRAS testing. We correlate PD-L1 expression in 10,005 tumours with patient age and sex, with tumour histological subtypes, with the sampling modality and type of tissue, and with the presence of other molecular alterations. PD-L1 expression testing was performed using the aforementioned assay; tumour proportion scores (TPS) of 1 and 50% were taken as cut-offs for low and high positivity, respectively. EGFR testing was performed using the cobas® EGFR Mutation Test v2. ALK testing was performed using the VENTANA ALK (D5F3) CDx Assay. KRAS testing was performed using pyrosequencing. TPS