Vinblastine and Carboplatin in Treating Young Patients With Newly Diagnosed or Recurrent Low-Grade Glioma

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