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-intraabdominal leiomyosarcomas

PATIENT CHARACTERISTICS:

Age:

• Not specified

Performance status:

• Zubrod 0-2

Life expectancy:

• Not specified

Hematopoietic:

• WBC 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