The present invention provides methods of treating a patient having a cancer comprising administering to the patient a soluble Fibroblast Growth Factor Receptor 1 (FGFR1) fusion protein such as an extracellular domain of an FGFR1 polypeptide linked to an Fc polypeptide or another fusion partner. The fusion protein may be administered at a dose of at least about 2 mg/kg body weight. In some embodiments, the patient has a fibroblast growth factor-2 (FGF-2) plasma concentration of at least 6 pg/ml. In some embodiments, the cancer is characterized by a Fibroblast Growth Factor Receptor 2 (FGFR2) having a ligand-dependent activating mutation.