Gastrointestinal stromal tumors II: medical oncology and tumor response assessment.

The finding of mutations of KIT in gastrointestinal stromal tumors (GISTs) and subsequent development of kinase-directed therapy in metastatic GIST serve as a touchstone for the translation of laboratory research into clinical therapeutics. A variety of novel developments have followed the discovery of clinical activity of kinase-directed therapy against GIST. Radiological assessment of GIST challenges the standard of care for assessing tumor responses, ie, Response Evaluation Criteria in Solid Tumors (RECIST). Furthermore, the determination of the relationship of specific KIT mutations and sensitivity and resistance to kinase-directed agents and the assessment of inhibitor levels and the quality of response to those agents have implications beyond the treatment of sarcomas. These discoveries and the next chapters in this developing story are discussed in this review.