Standard therapy for anaplastic oligodendrogliomas and mixed oligoastrocytomas includes radiation and chemotherapy. However, due to the potential long-term central nervous system toxicity from radiation, researchers speculate that it may be better to reserve radiation therapy for progressive disease. In addition, some patients with anaplastic oligodendroglioma and mixed oligoastrocytoma have unusually chemosensitive tumors. Previous research indicates that brain tumor patients with a deletion of the 1p chromosome have a higher response to the chemotherapy drug temozolomide.