• Biological effects of imatinib mesylate [ Designated as safety issue: No ]
  
• Rate of disease recurrence at 2 years [ Designated as safety issue: No ]
  
• Rates of objective response (complete, partial, and stable) [ Designated as safety issue: No ]
  
• Major toxicity (i.e., grade ≥ 3) [ Designated as safety issue: Yes ]
  
• Correlation of glucose transported expression and positron emission tomography (PET) interpretations [ Designated as safety issue: No ]
  
• Tumor changes observed on PET and correlation with size changes observed on conventional cross-sectional imaging [ Designated as safety issue: No ]
  
• Diagnostic accuracy of PET to predict disease recurrence [ Designated as safety issue: No ]
  

OBJECTIVES:

• Determine the progression-free survival of patients with primary or recurrent potentially resectable malignant gastrointestinal stromal tumor treated with neoadjuvant and adjuvant imatinib mesylate.
• Determine the objective response rate of patients treated with this drug.
• 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.

PROJECTED ACCRUAL: A total of 63 patients will be accrued for this study within 2 years.

DISEASE CHARACTERISTICS:

• Histologically confirmed malignant gastrointestinal stromal tumor

  • Potentially resectable primary disease OR

  • 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

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• Zubrod 0-2

Life expectancy:

• Not specified

Hematopoietic:

• WBC at least 3,000/mm^3
• Absolute neutrophil count at least 1,500/mm^3
• Platelet count at least 100,000/mm^3

Hepatic:

• 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

Renal:

• Creatinine no greater than 1.5 times ULN
• No uncontrolled chronic renal disease

Cardiovascular:

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

Other:

• 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

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• At least 28 days since prior biologic therapy
• No concurrent filgrastim (G-CSF) or sargramostim (GM-CSF)

Chemotherapy:

• At least 28 days since prior chemotherapy

Endocrine therapy:

• Not specified

Radiotherapy:

• At least 28 days since prior radiotherapy

Surgery:

• See Disease Characteristics

Other:

• 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