DISEASE CHARACTERISTICS: Histologically proven WHO grade III or IV glioma at primary diagnosis that enhance on preoperative imaging Glioblastoma Anaplastic astrocytoma Gliosarcoma Tumor volume no greater than 4.0 cm in maximum diameter on preoperative CT or MRI No prior histology of WHO grade I or II glioma Astrocytoma Oligodendroglioma No brainstem or infratentorial tumor No multifocal glioma Safe to treat tumor stereotactically No close proximity to critical structures, e.g., optic chiasm