Standard-Dose Osimertinib in EGFR-Mutated Non-Small-Cell Lung Adenocarcinoma With Leptomeningeal Disease.

Leptomeningeal disease (LMD) in epidermal growth factor receptor (EGFR)-mutant lung adenocarcinoma is associated with a poor prognosis and limited treatment options. Osimertinib is a potent third-generation EGFR tyrosine kinase inhibitor with confirmed CNS penetration. This study reports on outcomes of patients with EGFR-mutated non-small-cell lung cancer who developed LMD and were subsequently treated with osimertinib. We identified patients treated with osimertinib 80 mg PO daily under a compassionate access scheme across nine tertiary Australian institutes between July 2017 and July 2020. Patient demographics, tumor characteristics, and treatment history were collected. Median overall survival, median progression-free survival, disease control rates (DCR), and overall response rates (ORR) were assessed. Kaplan-Meier analysis was performed and descriptive statistics were used. Thirty-nine patients were analyzed of which 74% were female. Exon 19 deletions (49%) and L858R point mutations (41%) were the most common EGFR mutations. Forty-nine percentage of patients were Eastern Cooperative Oncology Group 1. The median duration of osimertinib therapy was 6 months. The extracranial DCR and ORR were 60% and 54%, and the intracranial DCR and ORR were 68% and 53%, respectively. Median overall survival was 10.5 months (95% CI, 8.17 to 15.05 months). There are limited treatment options for LMD in EGFR-positive lung cancer, and osimertinib at a dose of 80 mg daily is an active therapeutic option for these patients.