Surgical treatment of gastric GIST in the imatinib era Stiekema J1, Kol S1, Cats A2, van Coevorden F1, van Sandick J1 1 the 2 Nederlands Cancer Institute – Antoni van Leeuwenhoek hospital, Surgical Oncology the Nederlands Cancer Institute – Antoni van Leeuwenhoek hospital, Gastroenterology The introduction of the tyrosine kinase inhibitor imatinib (Glivec) has profoundly changed the treatment of gastrointestinal stromal tumours (GISTs). Neo-adjuvant imatinib treatment is strongly advised in patients with locally advanced or marginally resectable disease, where the risk of incomplete resection, tumour spill or significant postoperative morbidity is high. In metastatic GIST imatinib is considered treatment of primary choice, followed by secondary surgery in responding patients. In this study, the outcome of patients who were operated for a gastric GIST with or without neo-adjuvant imatinib was investigated. All patients surgically treated for a gastric GIST at our institute in the past twelve years (1999-2011) were included in this retrospective study. Patient, tumour, and treatment characteristics were retrieved from written and electronic patient files. A series of 48 patients was identified: 18 patients were treated with primary surgery (group 1) and 30 patients received imatinib prior to surgery (group 2). The median tumour size was 5.0 cm (range 1.5-19 cm) in group 1, and 13.5 cm (range 3.0-29 cm) in group 2. Most patients had local disease, but one patient in group 1 and seven patients in group 2 had metastatic GIST. Neo-adjuvant treatment led to a 25% reduction in tumour size (p < 0.001). Complete resection (RO) was achieved in all patients in group 1, and 27 patients (90%) in group 2. Wedge, partial and total gastric resection was required in 7 (39%), 10 (56%) and none of the patients (0%) in group 1, against 3 (10%), 13 (43%) and 4 patients (13%) in group 2. Multiple organ resection was performed in 1 patient (5%) in group 1, and in 10 patients (34%) in group 2. Postoperative complications (0% in group 1 and 20% in group 2; p= 0.043), were all transient with one complication in group 2 necessitating a re-intervention. Stratified for extent of resection, there was no significant difference in complication rate (p= 0.226). At a median follow-up of 30 months, 2 patients (11%) in group 1 and 5 patients (17%) in group 2 had recurrent or progressive disease. This was seen exclusively in patients with R1 or R2 resection or tumour spill during the operation. Five patients died of GIST. Median survival was not yet reached in either group. Conclusions: In this surgical series of gastric GIST patients, neo-adjuvant imatinib led to a significant reduction in tumour size, with a non-significant increase in postoperative complication rate. Considering the larger tumour size of patients in group 2, with a historical poor prognosis, imatinib proved its value in our series in achieving a longer progression free and overall survival.