Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically or cytologically confirmed glioblastoma multiforme

- Recurrent disease by CT scan or MRI

- No prior chemotherapy OR

- No more than 1 prior chemotherapy regimen in adjuvant setting or for recurrent
disease OR

- Histologically or cytologically confirmed anaplastic oligodendroglioma, mixed
oligoastrocytoma, anaplastic astrocytoma, or recurrent low-grade astrocytoma

- Failed prior radiotherapy

- No more than 1 prior chemotherapy regimen

- Failed adjuvant chemotherapy OR

- Failed first-line chemotherapy

- At least 1 bidimensionally measurable target lesion

- At least 2 cm on contrast-enhanced CT scan or MRI

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Performance status:

- ECOG 0-2

Life expectancy:

- Not specified

Hematopoietic:

- Neutrophil count at least 2,000/mm^3

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

Hepatic:

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

- AST and ALT no greater than 2.5 times ULN

- Alkaline phosphatase no greater than 2.5 times ULN

Renal:

- Creatinine less than 1.7 mg/dL

Cardiovascular:

- Cardiac function normal

- No ischemic heart disease within the past 6 months

- Normal 12-lead ECG

Other:

- No other prior or concurrent malignancy except cone-biopsied carcinoma of the cervix
or adequately treated basal cell or squamous cell skin cancer

- No unstable systemic disease

- No active uncontrolled infection

- No psychological, familial, sociological, or geographical condition that would
preclude study compliance

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception during and for 3 months after study

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- No concurrent anticancer biologic agents

- No concurrent cytokines (e.g., filgrastim [G-CSF] or sargramostim [GM-CSF])

Chemotherapy:

- See Disease Characteristics

- At least 4 weeks since prior chemotherapy (6 weeks for nitrosourea)

- No concurrent chemotherapy

Endocrine therapy:

- Must be on stable or decreasing dose of corticosteroids for at least 2 weeks

Radiotherapy:

- See Disease Characteristics

- At least 3 months since prior brain irradiation

- No prior high-dose radiotherapy (more than 65 Gy), stereotactic radiosurgery, or
internal radiotherapy unless the recurrence is histologically confirmed

- No concurrent radiotherapy

Surgery:

- Prior surgery for primary brain tumor within the past 3 months allowed provided one
of the following conditions are present:

- Postoperative imaging within 72 hours after surgery shows a clearly limited
target lesion of at least 2 cm

- Postoperative follow-up shows a progressive and measurable target lesion

- A second measurable target lesion is present outside the surgical area

Other:

- No concurrent warfarin or other anticoagulants

- No other concurrent anticancer agents

- No other concurrent investigational agents