Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed childhood brain tumor that is recurrent or refractory or for
which no standard chemotherapy exists

- High-grade glioma (anaplastic astrocytoma or glioblastoma multiforme)
(High-grade glioma stratum closed to accrual as of 01/08/2002)

- Low-grade glioma

- Medulloblastoma/primitive neuroectodermal tumor (PNET)

- Ependymoma

- Brainstem tumor or visual pathway glioma (with radiographic evidence only)
(Brainstem glioma stratum closed to accrual as of 12/21/2000)

- Evidence of recurrent or progressive disease after front-line therapy documented as
an increase in tumor size or appearance of new lesion(s) on MRI

- Patients who did not previously receive radiotherapy as front-line therapy are
eligible at time of second recurrence if the first recurrence was treated with
radiotherapy only

- Measurable disease in at least 2 dimensions by MRI

- Diffuse meningeal involvement not considered measurable if it is the only site
of disease

- Disease must not be limited to the meninges

- No metastases outside of the CNS

PATIENT CHARACTERISTICS:

Age:

- 21 and under at diagnosis

Performance status:

- ECOG 0-2

Life expectancy:

- At least 8 weeks

Hematopoietic:

- Absolute granulocyte count at least 1,000/mm^3

- Hemoglobin at least 8.0 g/dL (transfusion allowed)

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

Hepatic:

- Bilirubin less than 1.5 times upper limit of normal (ULN)

- SGPT no greater than 2.5 times ULN

- No significant hepatic illness

Renal:

- Creatinine within limits as defined below by age:

- Age 5 and under: less than 1.2 mg/dL

- Age 6 to 10: less than 1.5 mg/dL

- Age 11 to 15: less than 1.8 mg/dL

- Age 16 and over: less than 2.4 mg/dL

Cardiovascular:

- No significant cardiac illness

Pulmonary:

- No significant pulmonary illness

Other:

- No significant systemic illness or organ dysfunction that would preclude study

- No allergic reaction to platinum-containing compounds

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- At least 72 hours since filgrastim (G-CSF)

- No concurrent biologic therapy for brain tumor

Chemotherapy:

- See Disease Characteristics

- No prior carboplatin or lobradimil

- No more than 1 prior chemotherapy regimen for high-grade glioma, low-grade glioma, or
ependymoma

- No more than 2 prior chemotherapy regimens for medulloblastoma/PNET

- At least 4 weeks since prior nitrosoureas (2 weeks if also received stem cell/bone
marrow rescue)

- At least 2 weeks since any other prior myelosuppressive chemotherapy and recovered

- No other concurrent chemotherapy for brain tumor

Endocrine therapy:

- Concurrent corticosteroids for management of tumor-related edema allowed

Radiotherapy:

- See Disease Characteristics

- At least 6 weeks since prior radiotherapy to measurable disease and recovered

- No concurrent radiotherapy for brain tumor

Surgery:

- No concurrent surgery except for ventriculo-peritoneal shunt placement or revision

Other:

- At least 24 hours since prior vasodilating agents, angiotensin-converting enzyme
inhibitors, calcium channel blockers, or beta-blockers