Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed* low-grade glioma, including any of the following:

- Juvenile pilocytic astrocytoma (JPA) or pleomorphic JPA

- Diffuse astrocytoma, including any of the following subtypes:

- Fibrillary astrocytoma

- Gemistocytic astrocytoma

- Subependymal giant cell astrocytoma

- Pleomorphic xanthoastrocytoma

- Low-grade oligoastrocytoma

- Low-grade oligodendroglioma

- Low-grade glioma not otherwise specified NOTE: *Patients with chiasmatic lesions
who have contiguous extension of tumor into other regions of the visual pathway
by CT scan or MRI are eligible without histopathologic confirmation; repeat
biopsy required for patients with recurrent tumors that enhance but whose
initial tumor did not

- Measurable disease by radiography

- Meets any of the following criteria:

- Progressive nonresectable disease

- Any location in the brain

- Patients with a less than gross total resection are eligible provided they are
symptomatic from their tumor OR the risk from neurologic impairment with
progression is high enough to warrant immediate treatment

- Has undergone biopsy only

- Must have received ≥ 1 course of prior chemotherapy (for patients < 10 years of age)

- Prior chemotherapy optional (for patients ≥ 10 years of age)

- No type-1 neurofibromatosis

- No evidence of leptomeningeal dissemination

PATIENT CHARACTERISTICS:

Age

- 3 to 20

Performance status

- ECOG 0-2 OR

- Karnofsky 50-100% (for patients > 16 years of age) OR

- Lansky 50-100% (for patients ≤ 16 years of age)

Life expectancy

- At least 1 year

Hematopoietic

- Absolute neutrophil count ≥ 1,000/mm^3

- Platelet count ≥ 100,000/mm^3 (transfusion independent)

- Hemoglobin ≥ 10.0 g/dL (transfusions allowed)

Hepatic

- Not specified

Renal

- Not specified

Other

- Not pregnant

- Negative pregnancy test

- Fertile patients must use effective contraception

- Not in status epilepticus, coma, or requiring assisted ventilation prior to study
entry

- Patients with a seizure disorder are eligible provided they are on anticonvulsants
AND disease is well controlled

PRIOR CONCURRENT THERAPY:

Biologic therapy

- Not specified

Chemotherapy

- See Disease Characteristics

- Recovered from prior chemotherapy

- No concurrent chemotherapy

Endocrine therapy

- Concurrent dexamethasone allowed provided patient has been on a stable dose for ≥ 2
weeks prior to study entry

- Concurrent dexamethasone allowed for symptoms of increased intracranial pressure

Radiotherapy

- No prior radiotherapy

Surgery

- See Disease Characteristics

Other

- No other concurrent anticancer therapy