A phase II study to assess the efficacy of osimertinib in patients with EGFR mutation-positive NSCLC who developed isolated CNS progression (T790M negative or unknown) during first- or second- generation EGFR-TKI or systemic disease progression (T790M negative) after treatment with first- or second-generation EGFR-TKI and platinum-based chemotherapy (WJOG12819L)

Abstract Osimertinib is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) that has recently been established as a standard treatment option for chemotherapy-naive patients with EGFR mutation-positive non–small-cell lung cancer (NSCLC). However, only about one-half of patients who have received prior treatment with a first- or second-generation EGFR-TKI are eligible for osimertinib therapy because its indication in the second-line setting is limited to metastatic NSCLC positive for the T790M resistance mutation of EGFR. The dose-escalation part of a study in which patients received osimertinib at doses of 20 to 240 mg once daily after the development of resistance to first- or second-generation EGFR-TKIs revealed a response rate of 21% and a median progression-free survival of 2.8 months for individuals whose tumors were negative for EGFR T790M. We have now designed a phase II study of osimertinib for patients with EGFR mutation–positive NSCLC who develop isolated central nervous system progression (T790M-negative or unknown) after first- or second-generation EGFR-TKI therapy (cohort 1) or who develop systemic disease progression (T790M-negative) after first- or second-generation EGFR-TKI therapy and platinum-based chemotherapy (cohort 2). A total of 70 patients (cohort 1, n = 17; cohort 2, n = 53) will be enrolled in this study, which originated from a suggestion of a dedicated network for patients with lung cancer in Japan.