Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed supratentorial grade III or IV astrocytoma of 1 of the
following subtypes:

- Anaplastic astrocytoma

- Anaplastic oligodendroglioma

- Glioblastoma multiforme

- Measurable, contrast-enhancing, residual disease by MRI or CT scan

- Undergoing stereotactic biopsy for confirmation of tumor progression or
differentiation of tumor progression from treatment-induced effects

- Patients with prior low-grade glioma that progressed after prior radiotherapy
with or without chemotherapy and in need of stereotactic biopsy to confirm
high-grade glioma are eligible

- Must have received prior radiotherapy with or without chemotherapy

- Planning to continue methotrexate therapy after participation on this study

- No ascites or pleural effusions

PATIENT CHARACTERISTICS:

- Karnofsky performance status 60-100%

- Absolute neutrophil count ≥ 1,500/mm^3

- Platelet count ≥ 100,000/mm^3

- Bilirubin ≤ 2.0 mg/dL

- SGOT ≤ 4 times upper limit of normal

- Creatinine ≤ 2 mg/dL

- Creatinine clearance ≥ 50 mL/min

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No other malignancy within the past 5 years except curatively treated basal cell or
squamous cell skin cancer or carcinoma in situ

- Able to achieve hydration necessary for the use of methotrexate

- Mini mental state exam score at least 15

- No allergy to methotrexate

- No other concurrent infection or medical illness that would preclude study
participation

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- Recovered from prior therapy

- At least 3 months since prior radiotherapy

- At least 3 weeks since prior chemotherapy (6 weeks for nitrosoureas)

- At least 1 week since prior salicylates, nonsteroidal anti-inflammatory drugs, or
sulfonamides

- No concurrent prophylactic filgrastim (G-CSF) or sargramostim (GM-CSF)

- No concurrent chemotherapeutic agents

- No other concurrent investigational agents