A phase II study (WJOG12819L) to assess the efficacy of osimertinib in patients with EGFR mutation-positive NSCLC in whom systemic disease (T790M-negative) progressed after treatment with first- or second-generation EGFR TKIs and platinum-based chemotherapy

•Osimertinib cannot be used for T790M-negative NSCLC after 1st/2nd generation EGFR-TKI.•This study was initiated at the request of a dedicated network for patients with lung cancer in Japan.•We demonstrated that osimertinib had modest antitumor activity against those patients.