OUTLINE: This is a randomized, multicenter study. The right or left hemisphere of each patient's brain are randomized to one of two treatment arms. All patients receive whole brain radiotherapy 5 days a week over 2.5 weeks for a total of 12 fractions. Arm I: Patients receive radiotherapy to the left cerebral hemisphere daily for 6 days immediately following completion of whole brain radiotherapy. Arm II: Patients receive radiotherapy to the right cerebral hemisphere daily for 6 days immediately following completion of whole brain radiotherapy. Patients with extensive disease may also receive thoracic radiotherapy, if not administered previously. Patients are followed at 1, 3, 6, 9, and 12 months, and then every 6 months thereafter.