Dose optimization of tyrosine kinase inhibitors to improve outcomes in GIST

Tyrosine kinase inhibitors such as imatinib and sunitinib have greatly improved clinical outcomes for patients with gastrointestinal stromal tumors (GIST). Dose optimization of these agents is critical and involves multiple considerations, including ensuring a durable response, monitoring drug blood levels to confirm adequate dosing, deciding whether to use high-dose imatinib or switch to second-line sunitinib in the event of disease progression and appropriately managing treatment-associated side effects. Imatinib is the standard first-line therapy for unresectable or metastatic GIST and is also an option for the adjuvant treatment of resected disease. Despite the efficacy and safety of imatinib in patients with advanced GIST, some individuals develop primary or secondary resistance or intolerance to the drug. For patients with advanced disease, imatinib dose escalation to 800 mg/day is warranted in cases of disease progression on imatinib 400 mg/day. In addition, patients with documented KIT exon 9 mutations are likely to derive benefit from initial treatment with high-dose imatinib to improve clinical outcomes. For patients who fail imatinib, sunitinib is an effective treatment option. However, the decision to use either high-dose imatinib or sunitinib should be based on the underlying cause of failure on imatinib, KIT mutational status and on whether the patient is intolerant of or has developed a resistance to imatinib. In this article we review the existing literature supporting the use of imatinib and sunitinib in GIST to provide a current clinical perspective on how best to use these agents in the management of GIST to optimize patient outcomes.