Inclusion Criteria

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