Genomic Characterization of a RET Inhibitor-Resistant RET Fusion-Positive Lung Cancer by CSF Cell-Free DNA Hybrid Capture-Based Sequencing CNS metastases represent a disproportionate source of morbidity and mortality for patients with solid tumors. I RET i fusions are identified in 1%-2% of non-small-cell lung cancers, with I KIF5B-RET i being the most common.[2] These fusions are highly actionable, and the selective RET inhibitor selpercatinib was recently approved by the US Food and Drug Administration (FDA) in May 2020 for the treatment of patients with I RET i fusion-positive lung cancers. Lancet Oncol; 20: 1691-1701, 2019 24 Guo R, Schreyer M, Chang JC, et al: Response to selective RET inhibition with LOXO-292 in a patient with RET fusion-positive lung cancer with leptomeningeal metastases. [Extracted from the article]