Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed* low-grade glioma, including 1 of the following subtypes:

- Astrocytoma variants

- Fibrillary, protoplasmic, or mixed

- Pilocytic astrocytoma, including pilomyxoid variants

- Pleomorphic xanthoastrocytoma

- Infantile desmoplastic astrocytoma

- Ganglioglioma

- Oligodendroglial tumors

- Mixed glioma, including oligoastrocytoma NOTE: *Biopsy not required for patients
who have visual pathway tumors involving the optic nerves and/or optic
radiations (i.e., not isolated to the hypothalamus/chiasm)

- Biopsy proven focal low-grade gliomas of the brainstem with measurable disease
allowed

- No diffuse, intrinsic brainstem tumors

- Residual tumor visible on MRI

- Patients without NF-1 must meet the following criteria:

- Progressive disease after surgery/biopsy based on clear radiographic or clinical
evidence of progression OR gross residual tumor (> 1.5 cm²) after surgery/biopsy
that is felt to be a high risk to the patient for neurologic and/or visual
impairment if the tumor progresses

- Visual pathway tumors that are not isolated to the hypothalamus/chiasm and are
not biopsied must be a high risk to the patient for neurologic and/or visual
impairment

- Patients with NF-1 must have evidence of radiographic progression on MRI and/or
clinical worsening (e.g., worsening of ophthalmologic exam for visual pathway tumors)

- Meets 1 of the following criteria:

- Newly diagnosed disease

- Recurrent disease

- No ventriculoperitoneal shunt-related ascites

PATIENT CHARACTERISTICS:

- Karnofsky performance status (PS) 50-100% (for patients > 10 years of age) OR Lansky
PS 50-100% (for patients ≤ 10 years of age)

- Absolute neutrophil count ≥ 1,000/mm³

- Platelet count ≥ 100,000/mm³ (transfusion independent)

- Hemoglobin ≥ 8.0 g/dL (RBC transfusions allowed)

- Creatinine clearance or radioisotope glomerular filtration rate ≥ 70 mL/min OR
creatinine based on age, as follows:

- No greater than 0.8 mg/dL (for patients ≤ 5 years of age)

- No greater than 1.0 mg/dL (for patients 6-10 years of age)

- No greater than 1.2 mg/dL (for patients 11-15 years of age)

- No greater than 1.5 mg/dL (for patients > 15 years of age)

- Bilirubin ≤ 1.5 times upper limit of normal

- ALT ≤ 110 U/L

- Albumin ≥ 2 g/dL

- No history of allergy to carboplatin

- No hyponatremia requiring treatment

- No uncontrolled infection

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- No prior therapy except for corticosteroids and surgery (for patients with newly
diagnosed disease)

- Prior chemotherapy and/or radiotherapy in addition to surgery and corticosteroids
allowed (for patients with recurrent disease)

- Prior carboplatin and/or vinblastine allowed if there was no evidence of progressive
disease while on therapy and there were no dose reductions due to toxicity (for
patients with recurrent disease)

- At least 3 weeks since prior myelosuppressive chemotherapy (6 weeks for nitrosoureas)
and recovered (for patients with recurrent disease)

- At least 7 days since prior hematopoietic growth factors (for patients with recurrent
disease)

- At least 7 days since prior biological agents (for patients with recurrent disease)

- At least 9 months since prior external beam radiotherapy or gamma knife therapy that
included all target lesions (i.e., there is no restriction if a new lesion arises
outside the radiation field or a nonirradiated lesion progresses) and recovered (for
patients with recurrent disease)

- No other concurrent investigational drugs

- No other concurrent anticancer agents

- No other concurrent chemotherapy, radiotherapy, immunotherapy, or biological therapy

- No concurrent corticosteroids for antiemesis

- Concurrent steroids allowed for tumor edema/increased intracranial pressure provided
dose of dexamethasone is stable or decreasing for the past 7 days

- Concurrent physiologic or stress doses of steroids allowed for endocrine deficiencies