KIT and gastrointestinal stromal tumor: We hypothesized that by eliminating the selective pressure of continued pharmacologic therapy — which encourages the proliferation of resistant clones — by temporarily discontinuing treatment (a “washout” period), and using a second TKI such as regorafenib with established activity in GIST related in part to additional mechanisms of action beyond inhibition of KIT,13, response rates and survival times may be improved.