DISEASE CHARACTERISTICS:

• Histologically confirmed oligodendroglioma or mixed oligoastrocytoma

  • Grade 2-4
  • Recurrent disease
• Patients with mixed gliomas must have > 25% oligodendrogliomatous component

• Failed prior surgery, radiotherapy, and temozolomide or nitrosourea-based therapy

  • Progressive disease by MRI or CT scan
• Measurable or evaluable disease by MRI or CT scan
• More than 2 prior chemotherapy regimens for progressive or recurrent disease (pilot study only)
• Currently taking anticonvulsants which can induce cytochrome p450 (e.g., phenytoin, carbamazepine, barbiturates, or primidone (Phase I only)
• No prior or concurrent significant intratumoral hemorrhage

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• ECOG 0-2

Life expectancy

• Not specified

Hematopoietic

• Absolute neutrophil count at least 1,500/mm^3
• Platelet count at least 100,000/mm^3
• Hemoglobin at least 9 g/dL

Hepatic

• Bilirubin no greater than 1.5 mg/dL
• AST no greater than 3 times upper limit of normal

Renal

• Creatinine no greater than 2.0 mg/dL

Cardiovascular

• No myocardial infarction within the past 6 months
• No congestive heart failure requiring maintenance therapy for life-threatening ventricular arrhythmias
• No New York Heart Association class III or IV heart disease

Other

• No active uncontrolled infection
• No other severe concurrent disease that would preclude study or interfere significantly with interpreting potential drug-induced toxic effects
• No other active malignancy except nonmelanoma skin cancer
• No concurrent serious immunocompromised status unless related to concurrent steroids
• HIV-positive patients allowed
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for 6 months after study participation

PRIOR CONCURRENT THERAPY:

Biologic therapy

• At least 2 weeks since prior biologic noncytotoxic agents (e.g., thalidomide or interferon)
• No concurrent biologic therapy or immunotherapy for brain cancer

Chemotherapy

• See Disease Characteristics
• No prior interstitial chemotherapy, including carmustine wafers, unless separate lesion seen on MRI outside of prior treatment field
• At least 2 weeks since prior vincristine
• At least 4 weeks since other prior chemotherapy (6 weeks for nitrosoureas)
• No concurrent chemotherapy for brain cancer

Endocrine therapy

• At least 2 weeks since prior tamoxifen
• Concurrent corticosteroids allowed if dose stable for at least 1 week prior to study entry
• No concurrent hormonal therapy for brain cancer

Radiotherapy

• See Disease Characteristics
• At least 12 weeks since prior radiotherapy
• No prior stereotactic radiosurgery or interstitial brachytherapy unless separate lesion seen on MRI outside of prior treatment field
• No concurrent radiotherapy for brain cancer

Surgery

• See Disease Characteristics
• At least 2 weeks since prior surgery for initial or progressive disease and recovered
• No concurrent surgery for brain cancer

Other

• At least 2 weeks since prior isotretinoin
• At least 4 weeks since prior investigational agents

• No concurrent therapeutic warfarin or heparin

  • Low-dose warfarin and heparin (1 mg daily) allowed
• No other concurrent investigational or noninvestigational therapy for brain cancer