Takahama T, Azuma K, Shimokawa M, et al. - In this multicenter, investigator-initiated, single-arm phase 2 study (West Japan Oncology Group 8815L/ LPS), researchers tested the effectiveness of osimertinib in patients with non–small cell lung cancer (NSCLC) found to be positive for the T790M mutation of epidermal growth factor receptor (EGFR) by an analysis of plasma ctDNA after progression during treatment with EGFR tyrosine kinase inhibitors. Study participants were treated with osimertinib (80 mg/d) until disease progression. Two hundred seventy-six patients were screened for their T790M status with a liquid biopsy between June 2016 and November 2017. The outcomes show the effectiveness of liquid biopsy with the Cobas EGFR Mutation Test v2 for the identification of T790M. In clinical practice, plasma genotyping with this assay is useful when tumor sampling is not feasible for treatment selection.