Patients who upon staging workup are found to be without systemic involvement undergo one cycle of chemotherapy with cyclophosphamide, doxorubicin, vincristine, dexamethasone, and G-CSF. Cyclophosphamide, doxorubicin, and vincristine are administered intravenously on day 1. Dexamethasone is administered intravenously on day 1 and then orally thereafter with gradual discontinuation. G-CSF is administered subcutaneously daily beginning on day 2 and continuing for a total of 10 days or until blood counts have recovered to an acceptable level. Patients with evidence of cancer cells in their cerebrospinal fluid (CSF) will receive chemotherapy with intrathecal cytarabine twice weekly until no further evidence of cancer cells is found in the CSF, then once weekly for 6 weeks, and then monthly for 10 months. Seven to ten days following completion of one cycle of chemotherapy, patients undergo radiotherapy to the brain at a dose of 2.5 Gy daily for 5 days per week for approximately 4 weeks. Total dose to the whole brain and meninges is 30.0 Gy in 12 fractions, and total dose to the primary boost volume is 10.0 Gy in 4 fractions. During therapy, blood is drawn weekly and brain scans are performed every 3-12 weeks. An initial CSF sample will be obtained by lumbar puncture.