A Phase 2 Single-Arm Study of Osimertinib for Radiotherapy-Naive Central Nervous System Metastasis NSCLC: Results for the First-Line Cohort of the OCEAN Study (LOGIK 1603/WJOG 9116L)

Introduction: Osimertinib may be effective in treating central nervous system (CNS) metastasis, but its efficacy in treating radiation therapy (RT)-naive metastasis is unclear. The OCEAN study assessed the efficacy of osimertinib against RT-naive CNS metastasis in patients previously treated (T790M cohort) and untreated patients (first-line cohort) with EGFR mutation. Here, we report the results of the first-line cohort.Methods: Previously untreated patients with RT-naive CNS metastasis and EGFR mutation-positive NSCLC were treated with osimertinib. The brain metastasis response rate (BMRR), progression-free survival (PFS), and overall sur-vival in the first-line cohort were secondary end points.Results: A total of 26 patients were enrolled in the study between September 2019 and July 2020. The median age was 72.0 years with 80.8% female. There were 20 patients who had multiple CNS metastases. BMRR assessed by PAREXEL criteria was 76.9% (90% confidence interval [CI]: 63.3%-90.5%), BMRR assessed by Response Evaluation Criteria in Solid Tumors was 76.9% (95% CI: 54.0%- 99.8%), and median PFS of CNS metastasis was 22.0 months (95% CI: 9.7 mo-not reached). The overall response rate was 64.0% (95% CI: 45.2%-82.8%), median PFS was 11.5 months (95% CI: 6.9 mo-not reached), and median survival time was 23.7 months (95% CI: 16.5 mo-not reached). Paronychia and increased creatinine level were the most frequent nonhematological toxicities observed in 13 pa-tients (50%). Grade three and higher adverse events were less than 10%, and there were no treatment-related deaths. Pneumonitis was observed in five patients (19.2%).Conclusions: These results suggest that osimertinib is effective in untreated patients with RT-naive asymptomatic CNS metastasis in a clinical practice first-line setting.