Correlation between Classic Driver Oncogene Mutations in EGFR, ALK, or ROS1 and 22C3-PD-L1 ≥50% Expression in Lung Adenocarcinoma.

introductionTargeted somatic genomic analysis (EGFR, anaplastic lymphoma receptor tyrosine kinase gene [ALK], and ROS1) and programmed death ligand 1 (PD-L1) tumor proportion score (TPS) determined by immunohistochemistry (IHC) are used for selection of first-line therapies in advanced lung cancer; however, the frequency of overlap of these biomarkers in routine clinical practice is poorly reported.

methodsWe retrospectively probed the first 71 pairs of patients with lung adenocarcinoma from our institution. They were analyzed for PD-L1 by IHC using the clone 22C3 pharmDx kit (Agilent Technologies, Santa Clara, CA) and evaluated for co-occurrence of genomic aberrations and clinicopathologic characteristics.

resultsSurgical resection specimens, small biopsy (transbronchial or core needle) samples, and cytologic cell blocks (needle aspirates or pleural fluid) were tested. A PD-L1 TPS of at least ≥50% was seen in 29.6% of tumors. Of 19 tumors with EGFR mutations, ALK fluorescence in situ hybridization positivity, or ROS1 fluorescence in situ hybridization positivity, 18 had a PD-L1 TPS less than 50% versus only one tumor with a PD-L1 TPS of at least 50% (p = 0.0073). Tumors with a PD-L1 TPS of at least 50% were significantly associated with smoking status compared with tumors with a PD-L1 TPS less than 50% but were not associated with patient sex, ethnicity, tumor stage, biopsy site, or biopsy type/preparation.

conclusionsPD-L1 IHC can be performed on routine clinical lung cancer specimens. A TPS of at least 50% seldom overlaps with presence of driver oncogenes with approved targeted therapies. Three biomarker-specified groups of advanced lung adenocarcinomas can now be defined, each paired with a specific palliative first-line systemic therapy of proven clinical benefit: (1) EGFR/ALK/ROS1-affected adenocarcinoma paired with a matched tyrosine kinase inhibitor (∼20% of cases), (2) PD-L1-enriched adenocarcinoma (TPS ≥50%) paired with anti-PD-1 pembrolizumab (∼30% of cases), and (3) biomarker-negative (i.e., EGFR/ALK/ROS1/PD-L1-negative) adenocarcinoma paired with platinum doublet chemotherapy with or without bevacizumab (∼50% of cases).