Abstract
INTRODUCTION: Osimertinib is used as the first-line treatment for EGFR mutation-positive NSCLC. Nevertheless, its efficacy and safety in clinical practice remain to be fully elucidated and the pattern of progression and the optimal subsequent treatment after osimertinib remains unclear. METHODS: This was a multicenter prospective observational study. EGFR mutation-positive patients with NSCLC who started first-line osimertinib from September 2018 to August 2020 were enrolled and followed up until August 2022. RESULTS: A total of 583 patients received osimertinib. The median progression-free and overall survival were 20.0 (95% confidence interval [CI]: 17.6-21.7) months and 41.0 (95% CI: 37.1-44.1) months, respectively. Grade 3 or worse adverse events were observed in 136 patients (23.3%). Progression patterns were categorized as central nervous system only, oligo-progression, and multiple organs on the basis of the Response Evaluation Criteria in Solid Tumors-progressive disease and occurred in 37 (10.8%), 156 (45.4%), and 151 patients (43.9%). The patient's condition on progression was asymptomatic in 195 patients (56.7%). Osimertinib was continued in 163 patients (47.4%) after confirming progression. In clinically stable population with progressive disease (n = 247), survival after progression was 13.3 (95% CI: 10.9-16.4) months for those who continued osimertinib beyond progressive disease (n = 124), and 24.1 (95% CI: 17.7-34.0) months for those who discontinued osimertinib (n = 123) (hazard ratio = 2.01, 95% CI: 1.38-2.91, p = 0.0002). Platinum plus pemetrexed had the best overall survival benefits after osimertinib. CONCLUSIONS: First-line osimertinib was found to have good effectiveness comparable to that reported in pivotal studies. Nevertheless, osimertinib should be discontinued among those who develop progression. TRIAL REGISTRATION NUMBER: UMIN000038683.