Imatinib Mesylate in Treating Patients With Locally Advanced Gastrointestinal Stromal Tumor

DISEASE CHARACTERISTICS: Histologically confirmed gastrointestinal stromal tumor Locally advanced disease Potentially resectable disease* No tumor that can be completely resected (R0) with sufficient margins NOTE: *Multivisceral resection may be necessary Tumor must stain positive for c-Kit (CD117) or platelet-derived growth factor receptor-alpha (PDGFRA) by immunohistochemistry At least 1 site of measurable disease No known brain metastases PATIENT CHARACTERISTICS: Age 18 and over Performance status ECOG 0-3 Life expectancy Not specified Hematopoietic Platelet count > 100,000/mm^3 Absolute neutrophil count > 1,500/mm^3 Hepatic AST and ALT < 2.5 times upper limits of normal (ULN) (5 times ULN if hepatic metastases are present) Bilirubin < 1.5 times ULN No chronic active hepatitis No cirrhosis No other chronic liver disease Renal Creatinine < 1.5 times ULN No chronic renal disease Cardiovascular No New York Heart Association class III-IV cardiac disease No congestive heart failure No myocardial infarction within the past 6 months Immunology No active uncontrolled infection No known HIV positivity Other Not pregnant or nursing Negative pregnancy test Fertile patients must use effective barrier contraception during and for 3 months after completion of study treatment Must be medically fit to undergo surgery No other primary malignancy within the past 5 years except basal cell skin cancer, carcinoma in situ of the cervix, or a primary malignancy that is not currently clinically significant and does not require active intervention No gastrointestinal obstruction or major bleeding episode requiring immediate surgical intervention No uncontrolled diabetes No other severe or uncontrolled medical disease No significant history of noncompliance to medical regimens PRIOR CONCURRENT THERAPY: Biologic therapy No concurrent anticancer biologic agents Chemotherapy More than 4 weeks since prior chemotherapy (6 weeks for nitrosourea or mitomycin) unless disease is rapidly progressing No concurrent anticancer chemotherapy Endocrine therapy No concurrent systemic corticosteroid therapy unless approved by the study sponsor Radiotherapy More than 4 weeks since prior radiotherapy No prior radiotherapy to ≥ 25% of bone marrow Surgery More than 2 weeks since prior major surgery except tumor biopsy Other More than 4 weeks since prior investigational drugs unless disease is rapidly progressing No other concurrent anticancer therapy No other concurrent investigational agents No concurrent warfarin for therapeutic anticoagulation Concurrent low molecular weight heparin (e.g., enoxaparin sodium) or heparin for therapeutic anticoagulation allowed Concurrent mini-dose warfarin (e.g.,1 mg/day) for prophylaxis of central venous catheter thrombosis allowed