Durable response with a combination of imatinib and sorafenib in KIT exon 17 mutant gastrointestinal stromal tumor.

Imatinib, a selective KIT tyrosine-kinase inhibitor is considered standard first line therapy in metastatic gastrointestinal stromal tumors (GISTs). However, up to 40-50% of patients develop resistance to imatinib resulting in progression of disease. Other kinase inhibitors such as sunitinib, and most recently regorafenib have been approved as second and third line options respectively. Sorafenib has also been used following progression on standard therapies. Here we present the case of a patient with stage IV GIST of the rectum who had a rare exon 17 mutation treated prior to the approval of regorafenib. Therapy initially consisted of single agent imatinib, followed by sunitinib then sorafenib. Following continued progression of disease, the patient went on to develop stable disease for close to two years on a combination of sorafenib and imatinib.