P2.13-09 Efficacy and Safety of Osimertinib After Prior EGFR TKI: Analysis of Patients Underrepresented in Randomized Clinical Trials

Abstract

Osimertinib is a new standard of care in non-small cell lung cancer (NSCLC) after progression to an EGFR TKI in the presence of T790M mutation. Following results of the phase III study AURA 3, which led to the approval of osimertinib worldwide, we have conducted ASTRIS in Brazil. This is a phase IV, international, multicentric, open trial, with the aim of confirming the efficacy and safety of osimertinib at a dose of 80 mg daily, orally. Eligible patients presented with diagnosis of T790M-positive NSCLC on progression after prior EGFR TKI. Herein, we present the Brazilian experience at ASTRIS, including subsets that were underrepresented in the phase III trial. Eighty-eight patients were enrolled in Brazil between August 2015 and March 2017. The median age was 64 years (34-89), and most were females (66%). Fifty-four patients (61%) had received prior therapy with erlotinib, forty-two (48%) with gefitinib, and 3 (3%) with afatinib. Nineteen patients (22%) were exposed to a EGFR TKI more than 6 months before enrolment. Importantly, 11 patients (12.5%) presented with a PS of 2, 23 (26%) presented with brain metastases, and 3 with leptomeningeal disease. Exon 19 deletions were the most common primary mutation in EGFR, present in 55 cases (62.5%), followed by L858R in 24 cases (27%). Tumor samples were acquired from the primary tumor in 14 cases (45%) and in a metastatic site in 16 (52%); all other cases had T790M detected at plasma. After a median follow-up of 9.3 months, 26 progression events and 23 deaths were documented. The response rate was 58.2% (95%CI 46.6-69.2), and median progression-free survival was 9.4 months (95%CI 8.2-not reached). The 12-month overall survival was 69.7% (95%CI 56.5-79.6). Thirty patients (34%) presented an adverse event, 14 of which led to dose modification and 5 to treatment discontinuation. The most common adverse events were infection in 14 cases (15%), gastrointestinal and hematologic (4 cases each). Nineteen patients (22%) had a serious adverse event, mostly infections (14 cases). The profile of patients enrolled in Brazilian institutions highlights the presence of cases with poor PS, which was excluded in the AURA 3 trial. Despite these features, the efficacy and safety of osimertinib was confirmed, suggesting that results could be extrapolated to a broad range of subsets. This study also underscores the role of liquid biopsy in the detection of T790M, in detriment to tumor re-biopsy.