Noninvasive Detection of Polyclonal Acquired Resistance to FGFR Inhibition in Patients With Cholangiocarcinoma Harboring FGFR2 Alterations

ctDNA could be an effective means to longitudinally monitor for acquired resistance in FGFR2-altered IHC. The numerous acquired genetic alterations in FGFR2 suggest frequent polyclonal mechanisms of resistance that cannot be detected from single-site tissue biopsies.