Abstract
BACKGROUND: Epidermal growth factor receptor (EGFR) mutations are most common in Eastern Asia, and frequencies of 30-50% have been reported. EGFR-tyrosine kinase inhibitors (TKIs) are recommended as first-line therapeutic options for non-small cell lung cancer (NSCLC) with sensitizing EGFR mutations. Several immune checkpoint inhibitors have been successful in improving the outcomes of advanced lung cancer. The expression of programmed cell death-ligand 1 (PD-L1) on tumor cells plays an important role in predicting the efficacy of programmed cell death protein 1/PD-L1 inhibitors. The role of PD-L1 expression in tumors with EGFR mutation and its influence on clinical outcomes remain controversial. METHODS: Patients with newly diagnosed metastatic NSCLC with sensitizing EGFR mutations who received the standard treatment, ie, EGFR-TKIs for mutant adenocarcinoma as the first-line treatment, were enrolled in this retrospective study. EGFR mutations and PD-L1 expression levels were detected by Cobas RT-PCR and Dako 22C3 immunohistochemistry staining, respectively. RESULTS: From January 2011 to February 2019, 114 patients were enrolled. The average age was 62 years (range 34-92), and 45 (39.5%) patients were male. Among these patients, EGFR mutation analysis revealed exon 19 in-frame deletion in 55 (48.2%) patients, exon 21 L858R in 53 (46.5%) patients, and uncommon mutations in 6 (5.3%) patients. Among these patients with EGFR mutations, PD-L1 expression levels by tumor proportion score (TPS) were <1% in 54 (46.9%) patients, 1-49% in 50 (44.2%) patients, and ≥50% in 10 (8.8%) patients. All patients received EGFR-TKIs as first-line treatment, and in the Kaplan-Meier analysis, progression-free survival was not significantly different among groups with different PD-L1 expression status. CONCLUSION: For patients with metastatic NSCLC and EGFR mutations, PD-L1 expression is not uncommon, but no significant influence on clinical outcomes was observed in patients receiving standard initial treatment.