PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since prior immunotherapy At least 4 weeks since prior biologic therapy Chemotherapy: See Disease Characteristics At least 4 weeks since prior chemotherapy No prior temozolomide or dacarbazine Endocrine therapy: Not specified Radiotherapy: See Disease Characteristics At least 4 weeks since prior external beam radiotherapy At least 8 weeks since prior stereotactic radiosurgery Surgery: At least 2 weeks since prior brain biopsy, craniotomy, or other surgery