Association of PD‐L1 tumor proportion score ≥20% with early resistance to osimertinib in patients with EGFR ‐mutated NSCLC

BACKGROUND: The relationship between epidermal growth factor receptor tyrosine kinase inhibitor (EGFR‐TKI) resistance, including osimertinib, and programmed cell death‐ligand 1 (PD‐L1) expression status in EGFR‐mutated non‐small cell lung carcinoma (NSCLC) remains unclear. PATIENTS AND METHODS: We retrospectively analyzed 64 patients with unresectable advanced or metastatic NSCLC carrying EGFR exon 19 deletions (ex19del) or EGFR exon 21 L858R substitutions (L858R) who received osimertinib as the first‐line treatment. We compared progression‐free survival (PFS) between eligible patients with PD‐L1 tumor proportion scores (TPS) ≥20% and PD‐L1 TPS <20% using the Kaplan–Meier survival plots with a log‐rank test. Multivariate analysis was performed to examine the poor prognostic factors of PFS. RESULTS: The PD‐L1 TPS ≥20% group included 22 cases (median [range] age: 70.5 [33–86] years; 10 women [45.5%]; 11 current or ex‐smokers [50%]); ECOG performance status (PS) of 0–1/2/3/4 was noted in 16/4/1/1 patients, respectively. The PD‐L1 TPS <20% group included 42 patients (median [range] age 73 [43–88] years; 29 women [69%]; 12 current or ex‐smokers [28.6%]); ECOG PS of 0–1/2/3/4 was noted in 33/6/3/0 cases, respectively. The median PFS was 9.1 and 28.1 months in the PD‐L1 TPS ≥20% and PD‐L1 TPS <20% groups, respectively (log‐rank p = 0.013). Multivariate analysis revealed that PD‐L1 TPS ≥20% was associated with PFS (hazard ratio: 2.35, 95% confidence interval: 1.09–5.08, p = 0.030). CONCLUSION: PD‐L1 TPS ≥20% in patients with EGFR‐mutated NSCLC may be associated with early resistance to osimertinib.