Strong Programmed Death Ligand 1 Expression Predicts Poor Response and De Novo Resistance to EGFR Tyrosine Kinase Inhibitors Among NSCLC Patients With EGFR Mutation

This study evaluated whether tumor expression of programmed death ligand 1 (PD-L1) could predict the response of EGFR-mutated NSCLC to EGFR tyrosine kinase inhibitor (TKI) therapy.We retrospectively evaluated patients who received EGFR-TKIs for advanced NSCLC at the Guangdong Lung Cancer Institute between April 2016 and September 2017 and were not enrolled in clinical studies. The patients' EGFR and PD-L1 statuses were simultaneously evaluated.Among the 101 eligible patients, strong PD-L1 expression significantly decreased objective response rate, compared with weak or negative PD-L1 expression (35.7% versus 63.2% versus 67.3%, p = 0.002), and shortened progression-free survival (3.8 versus 6.0 versus 9.5 months, p < 0.001), regardless of EGFR mutation type (19del or L858R). Furthermore, positive PD-L1 expression was predominantly observed among patients with de novo resistance rather than acquired resistance to EGFR-TKIs (66.7% versus 30.2%, p = 0.009). Notably, we found a high proportion of PD-L1 and cluster of differentiation 8 (CD8) dual-positive cases among patients with de novo resistance (46.7%, 7 of 15). Finally, one patient with de novo resistance to EGFR-TKIs and PD-L1 and CD8 dual positivity experienced a favorable response to anti-programmed death 1 therapy.This study revealed the adverse effects of PD-L1 expression on EGFR-TKI efficacy, especially in NSCLC patients with de novo resistance. The findings indicate the reshaping of an inflamed immune phenotype characterized by PD-L1 and CD8 dual positivity and suggest potential therapeutic sensitivity to programmed death 1 blockade.