DISEASE CHARACTERISTICS:

• Histologically confirmed progressive, primary, intracranial, supratentorial, low-grade glioma including:

  • Astrocytoma
  • Oligodendroglioma
  • Mixed glioma
  • Optic pathway glioma*
  • Pontine glioma* NOTE: *Biopsy not required

• Patients with optic pathway glioma must also meet the following criteria:

  • Progressive loss of vision as defined by doubling of octaves
  • Visual acuity loss not explained by other causes
  • Increase in proptosis of greater than 3 mm
  • Increase in diameter of optic nerve of at least 2 mm on neuroimaging
  • Increase in distribution of tumor involving optic tracts or optic radiations as indicated by CT scan or MRI

PATIENT CHARACTERISTICS:

Age:

• 4 and over

Performance status:

• Karnofsky 70-100%

Life expectancy:

• More than 12 weeks

Hematopoietic:

• Absolute neutrophil count at least 1,500/mm^3
• Platelet count at least 100,000/mm^3
• Hemoglobin at least 10 g/dL

Hepatic:

• Bilirubin less than 1.5 times upper limit of normal (ULN)
• SGOT and SGPT less than 2.5 times ULN
• Alkaline phosphatase less than 2 times ULN

Renal:

• Creatinine less than 1.5 times ULN
• BUN less than 1.5 times ULN

Other:

• Must be neurologically stable
• No systemic disease
• No acute infection requiring IV antibiotics
• No frequent vomiting
• No other medical condition that would interfere with oral medication (e.g., partial bowel obstruction)

• No other prior or concurrent malignancies except:

  • Surgically cured carcinoma in situ of the cervix
  • Basal or squamous cell skin cancer
• HIV negative
• No AIDS-related illness
• Not pregnant or nursing
• Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• No concurrent biologic therapy (growth factors or epoetin alfa)

Chemotherapy:

• At least 6 weeks since prior chemotherapy unless evidence of disease progression
• No other concurrent chemotherapy

Endocrine therapy:

• Not specified

Radiotherapy:

• At least 6 weeks since prior radiotherapy unless evidence of disease progression
• No concurrent radiotherapy

Surgery:

• At least 3 weeks since prior surgery unless evidence of disease progression
• Recovered from all prior surgery

Other:

• No other concurrent investigational drugs