RATIONALE: Sorafenib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth and by blocking blood flow to the tumor.

PURPOSE: This phase II trial is studying how well sorafenib works in treating patients with malignant gastrointestinal stromal tumor that progressed on or after previous treatment with imatinib mesylate.

OBJECTIVES:

Primary

• Determine the objective response rate (partial and complete response) in patients with imatinib mesylate-resistant malignant gastrointestinal stromal tumor treated with sorafenib.

Secondary

• Determine the toxicity of this drug in these patients.
• Determine the progression-free survival and overall survival of patients treated with this drug.
• Determine the activity of this drug in these patients.

OUTLINE: This is a multicenter study. Patients are stratified according to response to prior treatment with imatinib mesylate (imatinib mesylate-responsive disease vs primary imatinib mesylate-refractory disease).

Patients receive oral sorafenib twice daily on days 1-28. Courses repeat every 28 days in the absence of disease progression or unacceptable toxicity.

After completion of study treatment, patients are followed periodically.

PROJECTED ACCRUAL: A total of 42 patients will be accrued for this study.

DISEASE CHARACTERISTICS:

• Histologically confirmed gastrointestinal stromal tumor
• Not amenable to curative surgery
• Kit-expressing tumor
• Disease progression (i.e., new lesion or 20% increase in unidimensional tumor size) on or after treatment with imatinib mesylate AND meets 1 of the following criteria:
• Imatinib mesylate-responsive disease (achieved a minor, partial, or complete response to imatinib mesylate and subsequently developed disease progression during or after treatment with imatinib mesylate)
• Imatinib mesylate-refractory disease (never achieved a minor, partial, or complete response to imatinib mesylate before disease progression)
• Measurable disease, defined as ≥ 1 unidimensionally measurable lesion > 20 mm by conventional techniques OR > 10 mm by spiral CT scan
• Only site of measurable disease must be outside of previously irradiated area
• No known brain metastases

PATIENT CHARACTERISTICS:

Performance status

• ECOG 0-2

Life expectancy

• More than 3 months

Hematopoietic

• Absolute neutrophil count > 1,500/mm^3
• Platelet count > 100,000/mm^3

Hepatic

• Bilirubin normal
• AST and ALT < 2.5 times upper limit of normal

Renal

• Creatinine normal OR
• Creatinine clearance > 60 mL/min

Cardiovascular

• No symptomatic congestive heart failure
• No unstable angina pectoris
• No cardiac arrhythmia
• No uncontrolled hypertension

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No other malignancy within the past 5 years except nonmelanoma skin cancer or carcinoma in situ of the cervix
• No history of allergic reaction attributed to compounds of similar chemical or biological composition to sorafenib
• No ongoing or active infection
• No psychiatric illness or social situation that would preclude study compliance
• No other uncontrolled illness

PRIOR CONCURRENT THERAPY:

Biologic therapy

• No prior angiogenesis inhibitors
• No immunotherapy after the last dose of imatinib mesylate

Chemotherapy

• No chemotherapy or chemoembolization therapy after the last dose of imatinib mesylate

Radiotherapy

• See Disease Characteristics
• At least 4 weeks since prior radiotherapy and recovered

Other

• At least 14 days since prior imatinib mesylate
• No prior sorafenib
• No prior inhibitors of MAPK-signaling intermediates
• No other investigational agent after the last dose of imatinib mesylate
• Concurrent anticoagulation therapy with warfarin allowed provided the following criteria are met:
• On a therapeutic stable warfarin dose
• INR ≤3
• No active bleeding or pathologic condition that confers a high risk of bleeding
• No concurrent combination antiretroviral therapy for HIV-positive patients
• No concurrent administration of any of the following:
• Enzyme-inducing antiepileptic drugs (e.g., carbamazepine, phenytoin, or phenobarbital)
• Hypericum perforatum (St. John''''s wort)
• Rifampin
• No other concurrent anticancer agents or therapies