All study participants will undergo standard, pre-treatment clinical evaluations that include: complete clinical/neurologic exam, performance status assessment, systemic staging, and diagnostic MRI of the brain. The baseline neurocognitive function (NCF) will be assessed by a short (20-30 minute) online test battery that can be completed by patients at home. All study participants will be randomized to receive radiosurgical or whole-brain radiation treatment for their brain metastases. All patients will have treatment response assessments every 10-12 weeks consisting of a clinical/neurologic exam, performance status evaluation, disease re-staging (if indicated), and diagnostic MRI of the brain. If progressive disease is identified (radiographic progression of treated lesions or new brain lesions), the patients will be considered for "salvage" therapy which will primarily consist of SRS, WBRT, surgery±brachytherapy or best supportive care (e.g. steroids only). The preferred salvage therapy will be SRS provided that the re-treatment criteria are met. The NCF follow-up will start 2 weeks after completion of the initial SRS treatment and will repeat at 2-week intervals, irrespective of any salvage therapy that may be indicated. All study participants will be followed until death or withdrawal from the study.