Disclosed herein are methods of treating cancer in a subject, wherein the subject is known to possess at least one genetic alteration in RET, comprising administering to the subject a therapeutically effective amount of N-[3-[(6,7-dimethoxy-4-quinazolinyl)oxy]phenyl]-N’-[5-(2,2,2-trifluoro-1,1-dimethylethyl)-3-isoxazolyl]-urea, or a pharmaceutically acceptable salt thereof.本文揭示治療受試者之癌症之方法,其中已知該受試者在RET中具有至少一個遺傳變化,該方法包含向該受試者投與治療有效量N-[3-[(6,7-二甲氧基-4-喹唑啉基)氧基]苯基]-N'-[5-(2,2,2-三氟-1,1-二甲基乙基)-3-異噁唑基]-脲或其醫藥學上可接受之鹽。