A phase II study of osimertinib for patients with radiotherapy-naïve CNS metastasis of non-small cell lung cancer harboring EGFR mutations: The OCEAN study (LOGIK 1603/WJOG 9116L).

Abstract

9597 Background: Approximately 15%–30% of patients treated with EGFR-TKIs experience central nervous system (CNS) progression. Although radiotherapy is a standard treatment for CNS metastasis, the efficacy of radiotherapy against CNS is poor. The aim of OCEAN study was to assess the efficacy of osimertinib for patients with radiotherapy-naïve CNS metastasis of NSCLC harboring EGFR mutations. Methods: OCEAN study was two-cohort phase II trial, 65 patients (T790M cohort; 40 patients and first-line cohort; 25 patients) with radiotherapy-naïve CNS metastasis of EGFR mutation-positive NSCLC was included. Patients were treated with osimertinib 80 mg once daily. The primary endpoint was the response rate of brain metastasis (BMRR) assessed by the PAREXEL criteria. We set a threshold value of 50% and an expected value of 70% based on the overall response rate (ORR) of AURA trial. Based on one-sided alpha = 0.05 and power = 0.8, the sample size of T790M cohort was calculated to be 40. Key secondary endpoints were progression-free survival (PFS), and ORR, BMRR assessed by the RECIST criteria. We are exploratorily assessing the blood concentration of osimertinib at day 22, which considered to represent steady state. In this report, we present the results of T790M cohort. Results: Between October 2016 to July 2019, 40 participants were recruited in the T790M cohort. The median age was 66.5 with 30.0% male. Eight patients had symptomatic CNS metastasis and most patient had multiple CNS metastasis (77.5%). BMRR assessed by PAREXEL criteria was 66.7% (95%CI: 54.3 – 79.1%) and BMRR assessed by RECIST was 70.0% (95%CI, 49.9 – 90.1%). Median PFS was 7.1 months (95%CI, 3.4 – 13.6 months) and ORR assessed by RECIST was 40.5% (95%CI, 24.7 – 57.9%). Treatment related pneumonitis was observed in 4 patients (10.0%). There was no grade 3 or higher toxicities that were found in more than 10%. Conclusions: This first study assessed the efficacy of osimertinib for patients with radiotherapy-naïve CNS metastasis of EGFR T790M mutation-positive NSCLC. The OCEAN study met primary endpoint. The results of this study suggested that patients with brain metastasis harboring EGFR T790M mutations had better to receive osimertinib prior to brain radiotherapy. Clinical trial information: 071180017 .