FGFR1 and neoplasm: An analysis of circulating tumor DNA (ctDNA) from patients enrolled in the MONALEESA-2 trial of ribociclib demonstrated that patients with FGFR1 amplification exhibited a shorter PFS compared to patients with wild-type FGFR1, thus suggesting FGFR1 as a mechanism of drug resistance to CDK 4/6 inhibitors and hormone therapy [42].