RATIONALE: Stereotactic radiation therapy may be able to deliver x-rays directly to the tumor and cause less damage to normal tissue.

PURPOSE: Phase II trial to study the effectiveness of stereotactic radiation therapy in treating patients who have brain metastases.

OBJECTIVES: I. Determine the efficacy of stereotactic radiosurgery without whole brain radiotherapy in elderly patients or patients with poor performance status who have brain metastases. II. Determine the neurologic function in these patients after receiving this treatment regimen. III. Determine the quality of life in these patients with this treatment regimen.

OUTLINE: Patients undergo stereotactic head frame placement, followed by stereotactic radiosurgery using Gamma Knife, on day 1. Quality of life is assessed one week prior to and one week after treatment, and then at 2, 4, 6, 8, 10, and 12 months. Patients are followed at one week, at 2, 4, 6, 8, 10, and 12 months, every 4 months for one year, and then every 6 months for 3 years.

PROJECTED ACCRUAL: Approximately 52 patients will be accrued for this study within 2 years.

• Radiation: radiation therapy
• Radiation: stereotactic radiosurgery

DISEASE CHARACTERISTICS: Patients with 1-4 sites of brain metastases Confirmed by MRI with gadolinium texaphyrin scan within two weeks of study If solitary metastases, diameter must be 40 mm or less If multiple metastases, one site may be greater than 30 mm, while all others must be less than 30 mm No metastases in the brainstem or within 5 mm of optic nerves or chiasm Prior surgical resection of metastases allowed if radiographically visible residual disease No prior cranial radiotherapy Patients must be over 65 years of age OR Over 18 years of age with Karnofsky performance status 40-60% All primary histologies allowed except the following: Lymphomas Leukemia Multiple myeloma Small cell lung cancer Germ cell tumors Extracranial disease allowed

PATIENT CHARACTERISTICS: Age: See Disease Characteristics Performance status: See Disease Characteristics Life expectancy: Not specified Hematopoietic: Hemoglobin greater than 8 g/dL Absolute neutrophil count greater than 1,000/mm3 Platelet count greater than 50,000/mm3 Hepatic: Not specified Renal: Not specified

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: Prior chemotherapy allowed Endocrine therapy: Not specified Radiotherapy: See Disease Characteristics Prior or concurrent radiotherapy to noncranial sites allowed Surgery: See Disease Characteristics