Comparison of PD-L1 Assays in Non-small Cell Lung Cancer: 22C3 pharmDx and SP263

While the PD-L1 22C3 pharmDx assay is an FDA-approved diagnostic assay for pembrolizumab use, not every pathology laboratory has the Dako Autostainer to use this assay. Since Ventana BenchMark platforms are more common, the Ventana SP263 assay can be used to inform treatment decisions involving nivolumab and pembrolizumab in non-small cell lung cancer (NSCLC). However, some studies have shown discordant results between the two assays. This study aimed was to compare PD-L1 expression using these two assays. A total of 100 samples from consecutive cases of resected NSCLC were tested using the two PD-L1 assays. The agreement rates of the two assays were 88-97% at various cut-offs. There was no significant difference between 22C3 and SP263 in tumour proportion score (p=0.455). The SP263 assay can be used in the place of the 22C3 assay for PD-L1 testing, for guiding therapy with PD-1 axis inhibitors in NSCLC.