DISEASE CHARACTERISTICS: Histologically confirmed gastrointestinal stromal tumor Distantly metastatic or unresectable disease Visceral or intra-abdominal primary disease Immunohistochemical documentation of CD117 expression No known brain metastasis

PATIENT CHARACTERISTICS: Age: 15 and over Performance status: Zubrod 0-3 Life expectancy: Not specified Hematopoietic: Absolute neutrophil count at least 1,000/mm3 Platelet count at least 100,000/mm3 Hemoglobin at least 9 g/dL (transfusion allowed) Hepatic: Bilirubin no greater than 1.5 times upper limit of normal (ULN) SGOT or SGPT no greater than 2.5 times ULN (5 times ULN if liver metastases present) No uncontrolled chronic liver disease Renal: Creatinine no greater than 1.5 times ULN No uncontrolled chronic renal disease Cardiovascular: No New York Heart Association class III or IV heart disease No congestive heart failure No myocardial infarction within the past 2 months Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective barrier contraception during and for up to 3 months after study participation No other severe and/or uncontrolled medical disease No uncontrolled diabetes No active uncontrolled infection (e.g., HIV) No medical or psychological condition that would preclude study participation No other prior malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, or stage I or II cancer in complete remission

PRIOR CONCURRENT THERAPY: Biologic therapy: At least 28 days since prior biologic therapy and recovered No concurrent anti-cancer biologic therapy Chemotherapy: At least 28 days since prior chemotherapy and recovered No concurrent chemotherapy Endocrine therapy: Recovered from prior endocrine therapy Radiotherapy: Recovered from prior radiotherapy No concurrent radiotherapy Surgery: At least 14 days since prior major surgery and recovered Other: At least 28 days since prior investigational drug and recovered No concurrent therapeutic anticoagulation with warfarin Concurrent mini-dose oral warfarin (1 mg/day) allowed as prophylaxis for central venous catheter thrombosis Concurrent therapeutic anticoagulation with low-molecular weight heparin (e.g., enoxaparin) or other agents allowed No other concurrent investigational drugs