Inclusion Criteria

DISEASE CHARACTERISTICS:

- Pathologically confirmed low grade residual astrocytomas or other eligible residual
tumors of the brain interpreted as low grade (WHO grades I and II) such as the
following:

- Glial Tumors

- Astrocytic tumors

- Low grade astrocytoma (variants: fibrillary, protoplasmic,
gemistocytic)

- Pilocytic astrocytoma

- Pleomorphic xanthoastrocytomas

- Subependymal giant cell astrocytoma

- Infantile desmoplastic astrocytoma

- Low grade oligodendroglial tumors

- Low grade oligodendroglioma

- Low grade mixed gliomas

- Oligo-astrocytoma

- Neuronal Tumors

- Ganglioglioma (excluding tumors with anaplastic astrocytic components)

- Infantile desmoplastic ganglioglioma

- Chiasmatic-hypothalamic tumor without histologic confirmation

- All of the following diagnostic tests (radiological or clinical evidence of
progression, surgery, or confirmatory MRI) must be carried out within 6 weeks of
enrollment into this study

- Progressive disease following surgical excision based on clear radiological or
clinical evidence of progression, or an incomplete excision (less than 95% or greater
than 1.5 cm2) with necessity to begin treatment because of a risk of neurologic
impairment with progression

- Chiasmatic lesions that have contiguous extensions of tumor into other regions of the
visual pathways demonstrated on contrast MRI will be eligible for study without
histopathological confirmation

- Patients with neurofibromatosis who have radiographic diagnosis of
chiasmatic-hypothalamic tumor are eligible for the study, without requiring a biopsy
confirmation of tumor histology, but not unless tumor progression is documented
radiographically

- No intrinsic brain stem tumors of the pons or isolated optic nerve tumors without
definitive involvement of the optic chiasm

PATIENT CHARACTERISTICS:

Age:

- Under 10

Performance status:

- Not specified

Life expectancy:

- Not specified

Hematopoietic:

- Absolute neutrophil count greater than 1,000/mm^3 (arm II)

- Platelet count greater than 100,000/mm^3 (arm II)

Hepatic:

- Not specified

Renal:

- Creatinine less than 1.5 times upper limit of normal for age OR

- Creatinine clearance or radioisotope GFR greater than 70 mL/min or equivalent GFR as
determined by the institutional normal range

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- Not specified

Chemotherapy:

- No prior chemotherapy for the tumor

Endocrine therapy:

- Prior corticosteroid therapy allowed

Radiotherapy:

- No prior radiotherapy for the tumor

Surgery:

- See Disease Characterisitcs

Other:

- Prior diuretic therapy allowed