Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically or cytologically confirmed unresectable or metastatic gastrointestinal
stromal tumor (GIST)

- Primary (gastrointestinal or intra-abdominal origin) tumor

- At least 1 measurable lesion by x-ray, CT, MRI, ultrasound, or physical examination

- If lesions within prior radiation port are used as target lesions for response
assessment, those lesions must have demonstrated clear progression after
completion of radiotherapy

- No uterine or retroperitoneal sarcomas or non-intra-abdominal leiomyosarcomas

PATIENT CHARACTERISTICS:

Age:

- Not specified

Performance status:

- Zubrod 0-2

Life expectancy:

- Not specified

Hematopoietic:

- WBC (white blood count) at least 3,000/mm^3

- Platelet count at least 100,000/mm^3

Hepatic:

- Bilirubin no greater than 2 times upper limit of normal (ULN)

Renal:

- Creatinine no greater than 1.5 times ULN

Other:

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No medical or psychological conditions that would preclude study participation

- No major infection requiring systemic antibiotics

- No uncontrolled bacterial, viral, or fungal infection

- No other prior malignancy within the past 5 years except:

- Adequately treated basal cell or squamous cell skin cancer

- Adequately treated stage I or II cancer in complete remission

- Carcinoma in situ of the cervix

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- At least 30 days since prior biologic therapy

- Prior imatinib mesylate as adjuvant therapy or for metastatic disease allowed

Chemotherapy:

- No prior chemotherapy for GIST

- At least 30 days since other prior chemotherapy

Endocrine therapy:

- Not specified

Radiotherapy:

- See Disease Characteristics

- No prior radiotherapy for GIST

- No concurrent radiotherapy for GIST

- Concurrent palliative radiotherapy for painful metastases (encompassing a total
portal of no greater than 5 x 5 cm) allowed

Surgery:

- See Disease Characteristics

- At least 4 weeks since prior major surgery and recovered

Other:

- At least 30 days since prior investigational drugs