Osimertinib treatment based on plasma T790M monitoring in patients with EGFR-mutant non-small-cell lung cancer (NSCLC): EORTC Lung Cancer Group 1613 APPLE phase II randomized clinical trial

The APPLE trial aimed to evaluate the feasibility of longitudinal plasma epidermal growth factor receptor (EGFR) T790M monitoring for the best sequencing strategy of gefitinib and osimertinib.APPLE is a randomized, non-comparative, phase II study in patients with common EGFR-mutant, treatment-naive non-small-cell lung cancer including three arms: arm A (osimertinib upfront until RECIST progression, PD), arm B [gefitinib until emergence of circulating tumor DNA (ctDNA) EGFR T790M mutation by cobas EGFR test v2 or RECIST PD], and arm C (gefitinib until RECIST PD), and then switch to osimertinib in both arms. The primary endpoint is the progression-free survival (PFS) rate 'on osimertinib' at 18 months (PFSR-OSI-18) after randomization in arm B (H0: PFSR-OSI-18 of ≤40%). Secondary endpoints include response rate, overall survival (OS), and brain PFS. We report the results of arms B and C.From November 2017 to February 2020, 52 and 51 patients were randomized into arms B and C, respectively. Most patients were females (70%) and had EGFR Del19 (65%); one-third had baseline brain metastases. In arm B, 17% of patients (8/47) switched to osimertinib based on the emergence of ctDNA T790M mutation before RECIST PD, with a median time to molecular PD of 266 days. The study met its primary endpoint of PFSR-OSI-18 of 67.2% (84% confidence interval 56.4% to 75.9%) in arm B versus 53.5% (84% confidence interval 42.3% to 63.5%) in arm C, with a median PFS of 22.0 months versus 20.2 months, respectively. The median OS was not reached in arm B versus 42.8 months in arm C. Median brain PFS in arms B and C was 24.4 and 21.4 months, respectively.The serial monitoring of ctDNA T790M status in advanced EGFR-mutant non-small-cell lung cancer during treatment with first-generation EGFR inhibitors was feasible, and a molecular progression before RECIST PD led to an earlier switch to osimertinib in 17% of patients with satisfactory PFS and OS outcomes.