Aim: To explore the effect of preoperative imatinib mesylate (IM) in patients with unresectable or locally advanced primary gastrointestinal stromal tumor (GIST).
Methods: From January 2003 to January 2008, all patients affected by bulky localized GIST who presented at our institution were considered for preoperative IM with cytoreductive intent. Clinical, pathological and molecular characteristics were assessed and the rate of response recorded. Progression-free survival (PFS) was calculated according to Kaplan-Meier analysis.
Results: Fifteen patients (1 esophageal, 7 gastric, 3 duodenal, 4 rectal GISTs) received preoperative IM for a median of 9 months. All patients had tumor shrinkage, with a median size reduction of 34%. One patient had radiological complete response. In all cases an improvement of the originally planned surgical procedure was obtained: 3 patients initially considered unresectable underwent complete surgery; 7 patients with initial indication for extensive surgery were more conservatively operated on; 4 patients initially deemed at high perioperative risk underwent safe surgery. Due to the small sample size, no association between tumor shrinkage and tumor site, size, IM duration, mutational status and pathological response could be formally explored. PFS at 3 years from IM onset was 77%.
Conclusions: In unresectable or locally advanced GISTs, preoperative IM is a useful tool both to improve resectability and reduce surgical morbidity. It should be therefore always be considered before embarking on a major surgical procedure. The long-term impact of IM on PFS and survival is presently under investigation in multicenter prospective randomized trials.