First-line osimertinib in patients with epidermal growth factor receptor–mutant non–small-cell lung cancer and with a coexisting low allelic fraction of Thr790Met

The AZENT (NCT02841579) study aimed to assess the efficacy and safety of first-line osimertinib in patients with epidermal growth factor receptor(EGFR)mutation–positive advanced non–small-cell lung cancer (NSCLC) and with a coexisting low allelic fraction of Thr790Met. In this multicentre, single-arm, open-label, phase IIa study, patients with locally advanced or metastatic NSCLC harbouring centrally confirmedEGFR Thr790Met mutation received 80 mg osimertinib daily. The primary end-point was objective response rate (ORR). The secondary end-points included disease control rate (DCR), progression-free survival (PFS), overall survival (OS) and safety. Efficacy was assessed as per Response Evaluation Criteria in Solid Tumours, version 1.1. Blood samples collected at baseline, end of week 2 and disease progression were analysed using next-generation sequencing. As osimertinib was approved as a first-line therapy during the trial, this led to early termination of phase II; thus, analysis is considered exploratory. Twenty-two patients were enrolled and received osimertinib. All 22 patients were included in the efficacy and safety analysis. At the data cutoff, 10 (50%) patients remained on treatment. The median duration of follow-up was 24.4 months (interquartile range 12.9 to 26.0). The ORR was 77.3% (17/22 [95% confidence interval {CI} 54.6 to 89.3]). The DCR was 86.4% (19/22, [95% CI 65.1 to 97.1]). The median PFS was 23.1 months (95% CI 14.1 to NE). The median OS was 28·4 months (95% CI 25.6 to NE). Despite early study termination, osimertinib first-line therapy yields an overall PFS of 23.1 months in EGFR-mutant patients harbouring a coexisting low allelic fraction of EGFR Thr790Met mutation. •EGFR-TKI sensitising mutations, exon 19 deletion and Leu858Arg, co-exist with Thr790Met.•Benefit of first-line osimertinib results higher in patients with Thr790Met in low allelic frequency.•Osimertinib resistance still occurs due to secondary EGFR or KRAS mutations.