Clinical correlation and frequency of programmed death ligand-1 (PD-L1) expression in EGFR-mutant and ALK-rearranged non-small cell lung cancer (NSCLC).

8012 Background: PD-L1 expression has recently been associated with response to PD-1 blockade. Given recent clinical interest in combining PD-1/PD-L1 inhibitors with EGFR and ALK tyrosine kinase inhibitors (TKIs), we evaluated PD-L1 expression patterns and clinical outcomes in EGFR-mutant and ALK-positive patients (pts). Methods: PD-L1 (Clone E1L3N, Cell Signaling Technologies) and CD8 immunohistochemistry were performed on biopsy and resection specimens from pts with metastatic NSCLC. Membranous expression of PD-L1 in > 5% tumor cells was defined as positive. CD8+ tumor infiltrating lymphocytes (TILs) were evaluated using a 4-tier grading system (0-3). Results: We evaluated PD-L1 expression and CD8+ TILs in pts with metastatic, EGFR-mutant (N = 68) and ALK-positive (N = 28) NSCLC (Table). Median progression-free survival (mPFS) on EGFR TKIs was similar between PD-L1(+) and PD-L1(-) pts at baseline (6.7 vs. 13.2 months; P = 0.08), as was overall survival (mOS; 31.8 vs. 35.63 months; P = 0.307). mPFS on AL...