P1.14-44 Positive PD-L1 Expression Is Associated with Unfavorable Clinical Outcome in EGFR-Mutated Lung Adenocarcinomas Treated with EGFR-TKIs

Abstract

Clinical implication of programmed death ligand 1 (PD-L1) expression in oncogene-addicted non-small cell lung cancer treated with tyrosine kinase inhibitors (TKIs) is largely unknown. The objective of this study was to determine the frequency of PD-L1 expression and the clinical outcome according to PD-L1 expression in lung adenocarcinomas harboring EGFR mutation and treated with EGFR-TKIs. We retrospectively evaluated PD-L1 expression using 22C3 pharmDx assay in lung adenocarcinoma patients with EGFR mutations at two referral hospitals between January 2017 and June 2018. Samples were obtained from surgically resected tumors, small biopsy, or cytologic cell blocks. Of all 71 patients analyzed, 44 (58.7%) had PD-L1 tumor proportion score (TPS) of < 1%, 23 (30.7%) had PD-L1 TPS of 1%-49%, and 8 (10.7%) had PD-L1 TPS of ≥ 50%. Of the 37 patients treated with first-line EGFR-TKIs, PD-L1 TPS ≥ 1% was associated with a significantly decreased response rate, compared with PD-L1 TPS < 1% (45.7% vs. 67.3%, p=0.005). Furthermore, PD-L1 TPS ≥ 1% was associated with a significantly shorter median progression free survival, compared with PD-L1 TPS < 1% (9.3 months vs. 14.2 months, p = 0.024). Multivariate analysis showed that PD-L1 TPS ≥1% is independently associated with shorter PFS (hazard ratio 1.32, p=0.012). PD-L1 was positive in approximately 40% of patients with EGFR-mutated lung adenocarcinoma. Positive PD-L1 expression may be associated with unfavorable clinical outcome to EGFR-TKIs among those patients group.