FP12.01 PD-L1 Assessment in Cytology is Comparable to Histology in Predicting Treatment Response to Checkpoint Inhibitors in NSCLC

Abstract

Tumor PD-L1 expression is a key biomarker in determining first-line therapy in advanced NSCLC. PD-L1 testing was developed with histology samples; however cytology (effusions, exfoliative specimens, fine needle aspirates) is critical for diagnosis and predictive testing in a large proportion of this patient population. Prior studies indicated a similar distribution of PD-L1 expression levels and high concordance at least for the ≥50% cut-off value with PD-L1 IHC 22C3 pharmDx. We retrospectively examined the response to PD-1/PD-L1 immune checkpoint inhibitors (ICI) in patients with PD-L1 testing performed on cytology compared to histology.