This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Targeted Anticancer Drugs and Immunosuppressants, Subject name: Pharmacology
[{'content': 'Which of the following agents is recommended as first line drug for treatment of gastrointestinal stromal tumors (GIST)? \nSelect and explain. \nA. Sorafenib, B. Geftinib, C. Imatinib, D. Erlotinib', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Imatinib is drug of choice for GIST. Imatinib resistant cases can be treated with sunitinib. Tumors resistant to both imatinib and sunitinib are treated with regorafenib.', 'role': 'assistant'}]