Osimertinib is a molecularly targeted agent used to treat non-small cell lung cancer (NSCLC) patients with an epidermal growth factor receptor (EGFR) T790M mutation. However, its efficacy and safety profile when patients have poor performance status (PS) is unknown. Therefore, we conducted an open-label, multi-center, single-arm phase II study to evaluate its efficacy and safety in EGFR T790M mutation-positive NSCLC patients with Eastern Cooperative Oncology Group PS scores of between 2 and 4. Patients received 80 mg of osimertinib once daily. Our primary endpoint was progression-free survival. Eighteen patients were enrolled between June 2017 and November 2018. The median age was 77 years (range: 55-85 years). Ten, six, and two patients had PS scores of 2, 3, and 4, respectively. All patients had adenocarcinoma with common EGFR mutations and had been treated with first- or second-generation EGFR- tyrosine kinase inhibitors previously. The overall median progression-free survival was 7.0 months (90% confidence interval: 5.5-8.9 months). The overall response rate and median overall survival were 53% and 12.7 months, respectively. Moreover, improved PS scores were observed in 72% of the patients. Although the incidence of grade 3 adverse events was low, with no grade 4 or 5 events observed, three patients required treatment cessation due to the development of interstitial lung disease. Osimertinib therapy could be beneficial for EGFR T790M mutation-positive advanced NSCLC patients with poor PS. This trial was registered with the Japan Registry of Clinical Trials on March 12, 2019 (trial no. jRCT1041180081).
Keywords: EGFR T790M mutation-positive; Non-small-cell lung cancer; Osimertinib; Poor performance status.