The brain-to-plasma partition coefficient for futibatinib is unknown, and data for other FGFR inhibitors are sparse and indicate relatively modest CNS penetration.17–20 In oncogene-addicted non–small cell lung cancer, isolated CNS progression is associated with significantly lower detection of driver and resistance alterations in ctDNA as opposed to extra-CNS progression.21 Whether this finding is transferable to FGFR2 fusion–positive cholangiocarcinoma remains unclear. The gene discussed is FGFR2; the disease is cholangiocarcinoma.