Outcomes of first-line osimertinib treatment for epidermal growth factor receptor-mutated non-small cell lung cancer in clinical practice settings

Background: Real-world data on the clinical outcomes of first-line osimertinib treatment for non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutations is lacking. This study aimed to evaluate the treatment outcomes and the prognostic factors of osimertinib as first-line therapy in clinical practice settings.Methods: We retrospectively evaluated clinical outcomes of patients with EGFR-mutated NSCLC treated with osimertinib as first-line therapy across 12 institutions in Japan between August 2018 and March 2020.Results: Among 158 enrolled patients, the objective response rate (ORR) was 68% and the estimated median progression-free survival (PFS) was 17.1 months (95% confidence interval [CI], 14.5-19.7). Subgroup analysis showed that PFS in the group with high programmed death-ligand 1 (PD-L1) expression was significantly shorter than that in groups with low or no PD-L1 expression (10.1 vs. 16.1 vs. 19.0 months; p = 0.03). Univariate and multivariate analyses demonstrated that high PD-L1 expression was the only independent adverse prognostic factor of osimertinib outcome for PFS (hazard ratio, 2.71; 95% CI: 1.26-5.84; p = 0.01). In terms of the ORR, there was no statistically significant difference regardless of PD-L1 expression (67% vs. 76% vs. 65%; p = 0.51).Conclusion: Osimertinib showed favorable treatment outcomes in clinical practice. Although the ORR was similar regardless of PD-L1 expression, high PD-L1 expression could be an independent adverse prognostic factor related to PFS in osimertinib treatment.