LAUSR

OBJECTIVES Resistance to tyrosine-kinase inhibitors (TKIs) is a clinical challenge in patients with oncogene-driven non-small-cell lung cancers (NSCLC). We have analyzed the utility of next-generation sequencing (NGS) of cell-free circulating tumor DNA (ctDNA) to impact the clinical care of patients with TKI resistance. MATERIALS AND METHODS We conducted a multi-institutional prospective study including consecutive EGFR, ALK, or ROS1-altered NSCLC patients with TKI resistance from 12 Spanish institutions. Post-progression ctDNA NGS was performed by Guardant Health (Guardant360 assay). RESULTS We included 53 patients separated in 3 cohorts: 31 EGFR-mutant NSCLCs with first/second-generation TKI resistance (cohort 1), 15 EGFR T790M + NSCLCs with osimertinib resistance (cohort 2), and 7 ALK/ROS1-rearranged NSCLCs with crizotinib and/or next-generation TKI resistance (cohort 3). Besides Guardant360, 22 patients from cohort 1 (71%) underwent post-progression tumor biopsies and/or alternative plasma-based genotyping. In the entire study population, 34 patients (64%) had reliable evidence of tumor-DNA shed for resistance assessment, and 24 patients (45%) had actionable alterations. Target-independent pathogenic alterations were frequently detected, particularly at osimertinib resistance. Eleven patients (20%) received subsequent molecular-guided therapies indicated by plasma NGS alone (n = 9, 17%), or plasma NGS and tissue sequencing (n = 2, 4%), deriving the expected clinical benefit. Of these, 9 had EGFR T790 M mutation and received osimertinib, 1 had ALK G1202R mutation and received lorlatinib, and 1 had ROS1 G2032R mutation and received cabozantinib. Two additional cases from cohort 1 (6%) had undetectable EGFR T790 M by Guardant360 but were T790M + by tissue and BEAMing digital PCR respectively, and also received osimertinib. CONCLUSION NGS of ctDNA detects actionable alterations in a large proportion of oncogene-driven NSCLC patients with TKI resistance, and can be used to guide subsequent treatments as a complement or alternative to tissue or PCR-based plasma genotyping in the real-world clinical setting.