Predictors of Response to Targeted Therapies for Gastrointestinal Stromal Tumors

Abstract

Context.—The inhibition of oncogenic kinase signaling is a successful strategy to treat both hematologic and solid malignancies. Patients with chronic myelogenous leukemia, lung adenocarcinoma, renal cell carcinoma, and gastrointestinal stromal tumors are experiencing tremendous clinical benefits from targeted therapies in the form of kinase inhibitors. These drugs marked a revolution in cancer treatment, not only for their safety and efficacy, but also because they continue to expand our knowledge of the pathophysiology of cancer. Objective.—To provide a summary of the biologic predictors of gastrointestinal stromal tumor behavior and response to targeted therapies that currently help guide clinical decision making. Data Sources.—Published articles pertaining to the diagnosis, molecular genetics, prognostication, clinical behavior, and treatment of gastrointestinal stromal tumors, as well as experiences in a multidisciplinary sarcoma clinic. Conclusions.—In gastrointestinal stromal tumors, the strongest predictor of response to targeted therapies is the mutational status of KIT or PDGFRA. Patients whose tumors harbor a KIT exon 11 mutation benefit the most from imatinib mesylate therapy, in terms of response rate, progression-free survival, and overall survival. Conversely, tumors without detectable mutations in either gene (“wild-type” gastrointestinal stromal tumors) are generally not responsive to imatinib mesylate.