Phase II trial to study the effectiveness of neoadjuvant and adjuvant imatinib mesylate in treating patients who are undergoing surgery for primary or recurrent malignant gastrointestinal stromal tumor. Imatinib mesylate may stop the growth of tumor cells by blocking the enzymes necessary for their growth. Giving imatinib mesylate before and after surgery may shrink the tumor so it can be removed and may kill any tumor cells remaining after surgery.

OBJECTIVES:

I. Determine the progression-free survival of patients with primary or recurrent potentially resectable malignant gastrointestinal stromal tumor treated with neoadjuvant and adjuvant imatinib mesylate.

II. Determine the objective response rate of patients treated with this drug. III. Determine the safety of this drug in these patients.

OUTLINE:

Patients receive oral imatinib mesylate once daily. Treatment continues for 8 weeks in the absence of disease progression. Patients with disease progression are considered for immediate surgical resection. Otherwise, after 8 weeks, patients undergo surgical resection to debulk all gross tumor. Two to four weeks after surgery, patients receive oral imatinib mesylate once daily for 2 years.

Patients are followed every 3 months for 2 years and then every 6 months for 3 years.

Inclusion Criteria:

• Histologically confirmed malignant gastrointestinal stromal tumor

  • Potentially resectable primary disease

  • Potentially resectable recurrent disease

    • Local or intra-abdominal/pelvic metastatic disease

• Documented c-kit (CD117) expression by immunohistochemical analysis of either initial core specimen or, if recurrent disease, from original tumor block

• Primary disease must be visceral, intra-abdominal, or pelvic in origin

• At least 1 unidimensionally measurable lesion

  • At least 5 cm for primary disease
  • At least 2 cm for recurrent disease

• At least 1 viable core biopsy tumor specimen obtained within 8 weeks before registration

• Performance status - Zubrod 0-2

• WBC at least 3,000/mm^3

• Absolute neutrophil count at least 1,500/mm^3

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

• Bilirubin no greater than 1.5 times upper limit of normal (ULN)

• ALT/AST no greater than 2.5 times ULN

• No uncontrolled chronic liver disease

• Creatinine no greater than 1.5 times ULN

• No uncontrolled chronic renal disease

• No New York Heart Association class III or IV cardiac disease

• Must be able to lie still in the PET scanner for approximately 1-2 hours

• No uncontrollable hyperglycemia

• No medical or psychological condition that would preclude study participation

• No severe or uncontrolled medical disease

• No active uncontrolled infection

• No known or suspected hypersensitivity to any component of the study drug

• Any prior malignancy is allowed provided patient remains disease free from that malignancy

• Not pregnant or nursing

• Negative pregnancy test

• Fertile patients must use effective barrier contraception during and for 3 months after study participation

• At least 28 days since prior biologic therapy

• No concurrent filgrastim (G-CSF) or sargramostim (GM-CSF)

• At least 28 days since prior chemotherapy

• At least 28 days since prior radiotherapy

• See Disease Characteristics

• At least 28 days since prior investigational drugs

• At least 28 days since prior imatinib mesylate

• No concurrent therapeutic doses of warfarin

• Concurrent low-molecular weight heparin or mini-dose warfarin (1 mg per day) prophylaxis is allowed