Effect of early dose reduction of osimertinib on efficacy in the first-line treatment for EGFR-mutated non-small cell lung cancer.

Osimertinib is used as the first-line therapy for patients with epidermal growth factor receptor (EGFR)-mutated non-small cell lung cancer (NSCLC). However, early dose reduction is often required due to adverse events (AEs). This study aimed to evaluate the effect of early dose reduction of osimertinib on efficacy and safety. This was a retrospective study including patients with EGFR-mutated NSCLC who were started on osimertinib as the first-line therapy between August 2018 and December 2021. Patients whose doses were reduced to less than 80 mg/day within 6 months of osimertinib initiation or started at 40 mg/day were defined as the dose reduction group. The primary endpoint was progression-free survival (PFS). Factors affecting PFS were explored using the Cox proportional hazards model. A total of 85 patients were included in this study. No significant differences in patient characteristics were observed between the dose reduction (n = 25) and standard dose groups (n = 60). The median PFS in the dose reduction group was significantly prolonged compared with that in the standard dose group (26.0 months vs. 12.0 months, p = 0.03). Multivariable analysis of 84 patients, excluding a patient with unknown brain metastasis, revealed that EGFR exon 21 L858R mutation, malignant pleural effusion or pleural metastasis, liver metastasis, and dose reduction within 6 months were independent factors affecting PFS. Early dose reduction of osimertinib is an effective therapeutic strategy for prolonging PFS in patients with EGFR-mutated NSCLC.