• B van Veggel, J F Vilacha Madeira R Santos, S M S Hashemi, M S Paats, K Monkhorst, Heideman D A M DAM Amsterdam UMC, Vrije Universiteit Amsterdam, Pathology, Cancer Center Amsterdam, De Boelelaan 1117, 1081 HV, Amsterdam, the Netherlands., M Groves, T Radonic, E F Smit, E Schuuring, A J van der Wekken, and A J de Langen.
• Dept of Thoracic Oncology, Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX, Amsterdam, the Netherlands.
• Lung Cancer. 2020 Mar 1; 141: 9-13.

ObjectivesEpidermal growth factor receptor (EGFR) exon 20 insertions comprise 4-10 % of EGFR mutations in non-small cell lung cancer (NSCLC) and are associated with primary resistance to first and second generation EGFR tyrosine kinase inhibitors (TKIs). In vitro and preclinical animal studies have shown that osimertinib exerts antitumor activity against EGFR exon 20 mutation positive NSCLC. We report on a cohort of advanced stage NSCLC patients who harbor an EGFR exon 20 mutation and received osimertinib treatment.Material And MethodsTwenty-one patients were treated with osimertinib 80 or 160 mg once daily from April 2016 to June 2018, in four institutions in the Netherlands. Data were obtained retrospectively. Progression free survival (PFS), disease control rate (DCR), overall survival (OS) and objective response rate (ORR) were assessed using RECIST v1.1.ResultsThirteen patients received prior platinum-based chemotherapy, and three patients a first - or second generation EGFR TKI. We observed 1 partial response, 17 patients with stable disease and 3 with progressive disease as best response to osimertinib (ORR 5 %). Median PFS was 3.6 (95 % CI, 2.6-4.5) months. PFS did not differ for patients with co-occurring TP53 mutations (p = 0.937). The DCR at three months was 71 %. Median OS was 8.7 (95 % CI, 1.1-16.4) months.ConclusionOsimertinib has limited antitumor activity in patients with EGFR exon 20 mutated NSCLC, with an ORR of 5 %.Copyright © 2019 Elsevier B.V. All rights reserved.

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