This invention relates to three crystalline forms of N—[3-fluoro-4-((6-(methyloxy)-7-[(3-morpholin-4-ylpropyl)oxy]quinolin-4-yloxy)phenyl]—N′—(4-fluorophenyl)cyclopropane-1,1-dicarboxamide. Compound (I), designated as Form A, Form B, and Form C. The invention provides methods for treatment of cancer by exploiting the modulation of protein kinase activity. The invention also provides pharmaceutical compositions containing a crystalline form of Compound (I) and a pharmaceutically acceptable excipient.