Sueoka-Aragane N, Nakashima C, Yoshida H, et al. - Whether liquid biopsy has efficacy as a predictive marker for the third generation EGFR tyrosine kinase inhibitor (EGFR-TKI), osimertinib, was assessed in this prospective, multi-center, observational study. The objectives included: if the coexistence of variants other than T790 M was correlated with response to osimertinib as well as to evaluate the clinical utility of next-generation sequencing (NGS) with circulating tumor DNA (ctDNA) for better prediction of treatment efficacy. Participants were non-small cell lung cancer (NSCLC) cases who progressed post-treatment with EGFR-TKI, and with EGFR T790 M, were managed with osimertinib. In 54 of 55 available banked plasma samples, NGS was successful; presence of EGFR driver mutations was evident in 43 (80%) and T790 M in 32 (59%). In early resistance patients, there was a higher total number of alterations identified in plasma using NGS. Following acquired resistance to osimertinib, T790 M was lost in 32% of patients (6 out of 19). Findings indicate the likely promising utility of NGS of ctDNA as a tool to predict the efficacy of osimertinib in patients suffering from advanced NSCLC harboring EGFR T790 M.