PD-L1 Tumor Proportion Scoring in Lung Cancer

Benjamin Levy, MD, opens a discussion with Kamel Abou Hussein, MD, Nicholas Hornstein, MD, PhD, and Nicole Balmaceda, MD, on how biomarkers differ across tumor types, then explains how programmed death-ligand 1 (PD-L1) guides treatment in non-small cell lung cancer. His center reflexively tests PD-L1 by immunohistochemistry in all patients with squamous or adenocarcinoma histology, using the 22C3 assay and the tumor proportion score (TPS) rather than the combined positive score. Dr. Levy notes that PD-L1 first guided second-line checkpoint inhibitor use and now drives frontline decisions. At a TPS of 50% or higher, clinicians debate single-agent pembrolizumab vs chemotherapy plus pembrolizumab; below 50%, his team pairs chemotherapy with pembrolizumab, including for patients with a TPS of 0. He describes PD-L1 as a continuous variable, since patients with expression above 90% respond more often than those at 70%, and credits lung cancer and melanoma with leading the immunotherapy field.