The role of imatinib plasma level testing in gastrointestinal stromal tumor.

The management of patients with gastrointestinal stromal tumor (GIST) has markedly advanced over the past 10 years. Imatinib has exceptional activity in controlling gastrointestinal stromal tumor (GIST) due to inhibition of the constitutively active conformation of KIT and PDGFRA which is found in the majority of patients with GIST. Although some patients may experience prolonged disease control while on imatinib, most patients will develop imatinib resistance within 2-3 years on therapy. A recent retrospective analysis demonstrated a relationship between imatinib plasma levels and progression-free survival in patients with advanced GIST. Plasma imatinib levels in this study were unrelated to the daily administered dose of imatinib. A prospective trial is underway in order to evaluate whether modification of imatinib dose to achieve a target imatinib plasma level will impact patient outcome when compared to standard imatinib dosing in GIST ( http://www.clinicaltrials.gov , NCT01031628).  This review will explore the current available data on the relationship between imatinib plasma levels, response to treatment, and other prognositic factors as well as discuss the implications of this data for possible future therapeutic approaches.