Gleevec Administered Preoperatively to Reduce Gastrointestinal Stromal Tumor (GIST)

Inclusion Criteria: * GIST patient considered initially non-resectable as defined by one of the following: 1. when the surgical team considers that the risk of incomplete resection (R1 or R2) of a GIST is higher than 20% 2. when the resection of a GIST necessitates a highly morbid procedure 3. when a GIST is attached to 3 or more major intra-abdominal structures or to a major intra-abdominal blood vessel 4. when GIST is considered at very high risk of recurrence. This is the case when it is a recurrence or when the tumor is in very close contact with a structure that cannot be resected by surgery or when the patient has metastasis. * Outpatient is 18 years old or more * ECOG performance status 0, 1 or 2 * Immunohistochemical confirmation of KIT overexpression must exist at the study entry * Measurable disease on CT-Scan or MRI (ultrasound and/or operative finding are not acceptable) and response to RECIST criteria * Have a life expectancy of at least 6 months * Be willing and able to comply with the protocol (and surgery if required) for the duration of the study * Give written informed consent prior to study-specific screening procedure, with the understanding that the patient has the right to withdraw from the study at any time without prejudice Exclusion Criteria: * received Imatinib in the past * received a full course of radiotherapy within 3 months of inclusion in the study. A short course of radiotherapy to control bleeding is allowed. * received systemic chemotherapy within 4 weeks of inclusion in the study * received steroids for less than 4 weeks of inclusion in the study * pregnant or lactating women * women of childbearing potential with either a positive or no pregnancy test at baseline. Postmenopausal women must have been amenorrheic for at least 12 months to be considered of non-childbearing potential. * sexually active males or females (of childbearing potential) unwilling to practice contraception during the study * history of other malignancy within the past 5 years, except cured basal cell carcinoma of skin and cured carcinoma in-situ of uterine cervix * clinical or other evidence of CNS metastases * myocardial infarction within the last 3 months * any medical condition that contraindicates potential surgery * lack of physical integrity of the upper gastrointestinal tract, malabsorption syndrome or inability to take oral medication * any serious uncontrolled concomitant disease * any of the following laboratory values: 1. absolute neutrophil count \< 1.5 E+09/L 2. platelet count \< 80000 E+09/L 3. AST or ALT higher than 2 X normal * major surgery within 4 weeks prior to start of study treatment, or lack of complete recovery from effects of major surgery * patients with known or suspected hypersensitivity to one of the Gleevec components.