OUTLINE: Patients undergo whole-brain radiotherapy (WBRT) daily 5 days a week for 4.5 weeks. Beginning 30 days after WBRT is completed, patients receive high-dose dexamethasone IV on days 1-5 during course 1 and on day 1 only during all subsequent courses. Courses repeat every 28 days in the absence of disease progression or unacceptable toxicity.