Stereotactic Radiation Therapy With or Without Whole-Brain Radiation Therapy in Treating Patients With Brain Metastases

DISEASE CHARACTERISTICS: * Diagnosis of cerebral metastases meeting the following criteria: * One to three presumed brain metastases * Metastases must be from a histologically confirmed extracerebral site (e.g., lung, breast, prostate) * Histologic confirmation may have been from the primary tumor site, from another metastatic site (e.g., osseous metastasis, adrenal metastasis), or from the metastatic brain lesion(s) * Each lesion must measure less than 3.0 cm by contrast MRI of the brain performed within the past 21 days * Lesions must not be within 5 mm of the optic chiasm or within the brainstem * Eligibility for treatment with gamma knife or linear accelerator-based radiosurgery confirmed by a radiation oncologist * No primary germ cell tumor, small cell carcinoma, or lymphoma * No leptomeningeal metastases * Hormone receptor status not specified PATIENT CHARACTERISTICS: * Male or female * Menopausal status not specified * ECOG performance status 0-2 * Not pregnant * Negative pregnancy test * Fertile patients must use effective contraception * Male patients must continue to use contraception for 3 months after the completion of radiotherapy * No pacemaker or other MRI-incompatible metal in the body * No known allergy to gadolinium PRIOR CONCURRENT THERAPY: * More than 7 days since prior and no concurrent chemotherapy * No prior cranial radiotherapy * No prior resection of cerebral metastases * Concurrent hormonal agents, steroids, and/or anticonvulsants allowed