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