Surgery for Locally Unresectable Advanced GISTs Without Metastasis After Imatinib Therapy

Inclusion Criteria * Locally advanced unresectable GIST without metastasis at * EC junction requiring total gastrectomy, * Duodenum requiring Whipple operation; * Large GIST requiring multiviceral resection; * Rectum: requiring APR. * Histologically documentation with positive immunostaining for KIT (CD117) * Patient age ≥ 18 years old * ECOG performance status 0 or 1 * Patient must have the following post-operative laboratory values confirmed within 14 days prior to registration: * Creatinine ≤ 1.5 times the institution ULN (upper limit of normal) * WBC ≥ 3,000/mm3 * Platelets ≥ 100,000/mm3 * Total Bilirubin ≤ 1.5 times the institution ULN. NOTE: Patients with elevated bilirubin secondary to Gilbert's disease are eligible to participate in the study. * AST ≤ 2.5 times the institution ULN * ALT ≤ 2.5 times the institution ULN * Female of childbearing potential must have negative serum pregnancy test. -- -NOTE: Post-menopausal women must be amenorrheic for at least 12 months to be deemed not of reproductive potential. * Patient is willing to sign informed consent. Exclusion Criteria * Patient has received post-operative chemotherapy. * Patient has received post-operative radiation therapy. * Patient has received post-operative investigational treatment. * Patient has received prior therapy with imatinib, or any other molecular targeted or biological therapy. * Patient has had an active infection requiring antibiotics within 14 days prior to registration. * any prior malignancies for at least 5 years with potential evidence of recurrence (except for effectively treated basal cell or squamous carcinoma of the skin, carcinoma in-situ of the cervix that has been effectively treated by surgery alone, or lobular carcinoma in-situ of the ipsilateral or contralateral breast treated by surgery alone). * Patient is deemed by their treating physician to be at risk for recurrence from prior malignancies.New York Heart Association Class 3 or 4 cardiac diseases. * Patient is taking full dose warfarin. NOTE: The use of mini-dose warfarin (1 mg orally per day) for prevention of central line-associated deep venous thrombosis is permitted. * Presence of severe and/or uncontrolled concurrent medical disease (e.g., uncontrolled diabetes, uncontrolled chronic renal disease, uncontrolled liver disease, including chronic viral hepatitis judged at risk of reactivation, uncontrolled active infection, such as HIV infection, etc.). * Patient, if female and breastfeeding. NOTE: It is not known whether imatinib or its metabolites are excreted in human milk.