DISEASE CHARACTERISTICS:

• Histologically proven supratentorial low-grade (grade II) glioma of any of the following histologic subtypes:

  • Oligodendroglioma
  • Astrocytoma
  • Oligoastrocytoma

• Has undergone surgical resection or biopsy within 35 days after diagnosis of low-grade glioma

  • Study treatment must begin between 14 days and 4 months after surgical resection or biopsy
• Evaluable disease by gadolinium-MRI

PATIENT CHARACTERISTICS:

• Karnofsky performance status 60-100%
• Absolute neutrophil count ≥ 1,500/mm^3
• Platelet count ≥ 100,000/mm^3
• Hemoglobin ≥ 10 g/dL
• Creatinine < 1.5 times upper limit of normal (ULN)
• BUN < 1.5 times ULN
• Bilirubin < 1.5 times ULN
• SGOT < 2.5 times ULN
• Alkaline phosphatase < 2 times ULN
• Life expectancy > 12 weeks
• No nonmalignant systemic disease resulting in the patient being a poor medical risk
• No acute infection requiring intravenous antibiotics
• No frequent vomiting or medical condition that would interfere with oral medication intake (e.g., partial bowel obstruction)

• No other concurrent malignancies except surgically cured carcinoma in situ of the cervix or basal cell or squamous cell carcinoma of the skin

  • Prior malignancies must be in remission for ≥ 5 years
• No known HIV positivity
• No AIDS-related illness
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• No prior radiotherapy, interstitial brachytherapy, or radiosurgery for low-grade glioma
• No prior biological therapy or chemotherapy for low-grade glioma
• No other concurrent chemotherapy
• No concurrent radiotherapy or biological therapy
• No concurrent prophylactic growth factors
• No concurrent epoetin alfa
• No other concurrent investigational drugs