A Real World Treatment Study of Osimertinib: ASTRIS Study Korean Subgroup Analysis

ASTRIS (NCT02474355) is an open-label, single-arm, multination, real world treatment study, investigating the safety and efficacy of osimertinib in patients with T790M-positive advanced non-small cell lung cancer (NSCLC), who have previously received EGFR-TKI. We report the first results of Korean subset from ASTRIS which is the largest real world treatment study of osimertinib to date. Eligible patients had advanced NSCLC harboring a T790M mutation determined by local validated molecular tests, received prior EGFR-TKI therapy, acceptable organ and bone marrow function and no history of interstitial lung disease (ILD) or QTc prolongation. Enrollment of patients with asymptomatic, stable CNS metastases were permitted. Patients received osimertinib 80 mg once daily. The primary efficacy outcome was overall survival; other outcomes included investigator-assessed response rate (RR), progression-free survival (PFS) and time to treatment discontinuation (TTD). Safety assessment was also conducted. Data cut-off (DCO) was 3 November 2016; results from 1,217 patients in the global study have been presented previously (ASCO 2017 Abstract 9036). A total of 371 patients received at least one dose of osimertinib from 30 Korean sites (full analysis set); at DCO, 319 patients (81.4%) were ongoing and median follow-up time was of 3.1 (0–8) months. Baseline patients’ characteristics were median age 61.1 (27–85) years old, female 65.5%, PS 0/1 88%, prior chemotherapy 47%, prior radiotherapy 48%. Tissue was the most common specimen source to test T790M mutation as well as other EGFR mutations (287/371, 77.4%) and plasma was the next (39/371, 13.1%). Fifty two patients (13.3%) had discontinued treatment; median duration of exposure 3.3 (0–7) months, 30 pts (7.7%) had disease progression and 24 patients (6.5%) died. In patients evaluable for response, defined as at least one dose of osimertinib and one response assessment, the investigator-assessed RR was 72.1% (212/294; 95% CI 66.6 – 77.2). Due to limited follow-up period, OS, PFS, and TTD were immature to analyze. Adverse events (AEs) leading to dose modification and treatment discontinuation were reported in 26 patients (7%) and 14 patients (3.8%), respectively. Serious AEs were reported in 50 patients (13.5%) and AEs leading to death in 8 patients (2.2%). ILD/pneumonitis-like events were reported in 9 patients (2.4%), and QTc prolongation (>470ms) in 5 patients (1.3%). At DCO for the 1st interim analysis of ASTRIS, Korean subgroup results demonstrated similar clinical activities (RR) to that observed in the osimertinib clinical trial program with no new safety signals.