Abstract
INTRODUCTION: EGFR tyrosine kinase inhibitors (TKIs) are more effective than chemotherapy in patients with EGFR-mutant NSCLC. Disease progression on EGFR TKI therapy occurs most often owing to acquired resistance from the gain of an EGFR T790M mutation. Osimertinib, a third-generation EGFR TKI, significantly improves outcomes in patients with EGFR T790M mutation-positive NSCLC compared with platinum-pemetrexed chemotherapy. We retrospectively reviewed clinical outcomes for patients receiving osimertinib through a compassionate access program in New Zealand. METHODS: Patients with a biopsy-proven or plasma-circulating tumor-DNA-proven EGFR T790M mutation received osimertinib. Data on patient and tumor characteristics, treatments, and outcomes were collected retrospectively. Survival outcomes were calculated from the time of osimertinib commencement. RESULTS: A total of 39 patients were enrolled, and data from 37 patients were analyzed. EGFR T790M status was found from plasma samples in six of 37 (16%) patients. A total of 27 of 37 patients (73%) used osimertinib as a second-line treatment. At the time of data analysis, median follow-up was 18.8 months (range 1.5-29). Overall response rate was 70% (95% confidence interval [CI]: 53-84) (26 of 37). Progression-free survival (PFS) at 12 months was 62% (95% CI: 44.8-77.5), and median PFS was 14.6 months (95% CI: 12.4-16.8). Median overall survival was not reached. Osimertinib was well tolerated, with grade 1 gastrointestinal and skin toxicity as the most common adverse effects. Three patients required dose adjustments or cessation owing to toxicity. CONCLUSION: Osimertinib is an effective treatment for New Zealanders with EGFR T790M mutated NSCLC who have progressed after first or subsequent lines of therapy.