The present invention relates to the use of Fibroblast Growth Factor Receptor I (FGFR1) extracellular domain (ECD) polypeptides for treatment of cancers characterized by ligand dependent activating mutations in Fibroblast Growth Factor Receptor 2 (FGFR2). For example, the present invention relates to the treatment of endometrial cancers and other cancers wherein tumor cells express FGFR2 mutants in the IgII-IgIII hinge region or IgIII domain of the protein, such as at amino acid positions 252 and/or 253.
