RATIONALE: Radiation therapy uses high-energy x-rays to damage tumor cells. Combining radiation therapy with a corticosteroid, such as dexamethasone, may be an effective treatment for non-Hodgkin's lymphoma.

PURPOSE: Phase II trial to study the effectiveness of radiation therapy and high-dose dexamethasone in treating older patients with primary CNS non-Hodgkin's lymphoma.

OBJECTIVES:

• Assess the effectiveness of high-dose dexamethasone after whole-brain radiotherapy in maintaining response and preventing recurrence in elderly patients with primary central nervous system non-Hodgkin's lymphoma.
• Assess the toxic effects of this regimen in these patients.
• Assess the survival rate of patients after this regimen.
• Identify the anatomic rates of recurrence and frequency of systemic involvement in patients treated with this regimen.
• Identify the factors that appear to be associated with outcome in patients treated with this regimen.

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.

Patients are followed at 1 month after radiotherapy, every 3 months for 2 years, every 6 months for 3 years, and then annually thereafter.

PROJECTED ACCRUAL: A total of 28 patients will be accrued for this study within 6 years.

DISEASE CHARACTERISTICS:

• Pathologically confirmed non-Hodgkin's lymphoma with intracranial lesions

  • Intraocular lymphoma eligible, if not sole site of disease
  • No occult systemic lymphoma

• Measurable or evaluable disease by CT scan or MRI

• No neoplastic meningitis or gross spinal cord involvement

PATIENT CHARACTERISTICS:

Age:

• 70 and over

Performance status:

• ECOG 0-3

Other:

• No prior history of lymphoma
• No other active malignancy except basal cell skin cancer or carcinoma in situ of the cervix
• HIV negative
• No active peptic ulcer disease
• No uncontrolled diabetes mellitus
• No active pancreatitis
• No active bleeding
• No poorly controlled major psychiatric illness
• No serious uncontrolled infection

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• No prior bone marrow transplantation

Chemotherapy:

• No prior chemotherapy

Radiotherapy:

• No prior radiotherapy to the brain or head and neck region

Surgery:

• No prior transplantations (renal, hepatic, or cardiac)