DISEASE CHARACTERISTICS:

• Histologically confirmed neuroendocrine tumor

  • Carcinoid tumor OR islet cell carcinoma/other well-differentiated tumor

    • No anaplastic or high-grade histology
  • Metastatic disease
• Measurable disease
• No thyroid carcinoma of any histology, thymoma, or pheochromocytoma/paraganglioma
• No known brain metastases

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• ECOG 0-2

Life expectancy

• At least 24 weeks

Hematopoietic

• Absolute neutrophil count ≥ 1,500/mm^3
• Platelet count ≥ 100,000/mm^3
• No bleeding diathesis

Hepatic

• Bilirubin ≤ 2 times upper limit of normal (ULN)
• AST ≤ 3 times ULN (5 times ULN if liver metastases are present)
• INR normal
• PTT normal

Renal

• Creatinine ≤ 1.5 times ULN

Cardiovascular

• No poorly controlled hypertension
• No symptoms of congestive heart failure
• No unstable angina pectoris
• No cardiac arrhythmia

Gastrointestinal

• Able to swallow capsules intact
• No gastrointestinal tract disease resulting in an inability to take oral medication (e.g., dysphagia)
• No requirement for IV alimentation
• No active peptic ulcer disease

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No ongoing or active infection
• No psychiatric illness or social situation that would preclude study compliance
• No other invasive malignancy within the past 3 years except adequately treated basal cell or squamous cell skin cancer or carcinoma in situ of the cervix
• No other uncontrolled illness

PRIOR CONCURRENT THERAPY:

Biologic therapy

• At least 4 weeks since prior interferon

Chemotherapy

• No more than 1 prior systemic chemotherapy regimen

  • Chemoembolization is not considered systemic chemotherapy
• At least 4 weeks since prior chemoembolization

Endocrine therapy

• Prior or concurrent octreotide for symptomatic treatment allowed

Radiotherapy

• At least 3 weeks since prior radiotherapy

Surgery

• At least 4 weeks since prior major surgery
• No prior procedures adversely affecting intestinal absorption

Other

• Recovered from all prior therapy
• At least 4 weeks since prior hepatic artery embolization
• No other prior systemic therapy
• No other concurrent investigational treatment
• No concurrent combination antiretroviral therapy for HIV-positive patients
• No concurrent enzyme-inducing anticonvulsants (e.g., carbamazepine, phenobarbital, or phenytoin)
• No concurrent rifampin
• No concurrent Hypericum perforatum (St. John's wort)

• No concurrent therapeutic anticoagulation

  • Concurrent prophylactic anticoagulation (i.e., low dose warfarin) of venous or arterial access devices allowed provided requirements for INR or PTT are met