KIT and gastrointestinal stromal tumor: However, in a phase II randomized trial examining dose selection in 946 patients with advanced GIST, patients whose tumors expressed an exon 9 KIT mutation, treated with a daily dose of 800 mg of Imatinib (versus 400 mg), experienced a significantly superior PFS (P = 0.0013) with a reduction of relative risk of 61% [31].