DISEASE CHARACTERISTICS: Histologically proven primary malignant gliomas including the following: Glioblastoma multiforme Gliosarcoma Anaplastic astrocytoma Anaplastic oligodendroglioma Anaplastic infiltrating glioma Mixed malignant gliomas Must show evidence of tumor recurrence or progression on at least 2 serial enhanced MRI scans Must have measurably enhancing residual disease on MRI or CT scan of brain