KIT and gastrointestinal stromal tumor: Given the exquisite sensitivity of GIST cells to imatinib in vitro [10], and the dramatic clinical effect of imatinib administered to people in the first-line setting [11], particularly in tumors carrying mutations in KIT exon 11 (representing approximately 65% of all patients), it is unclear why complete responses are comparatively rare and the cure rate so low, with the vast majority of patients ultimately dying with advanced disease.