Inclusion Criteria:

• 1. Patients 18 years or older
• 2. One to three brain metastases targets, all smaller than 3 cm in diameter (intact or resected tumor bed)
• 3. Eastern cooperative Oncology Group (ECOG) performance status 0-2 (score of 0, no symptoms; 1, mild symptoms; 2, symptomatic, \<50% in bed during the day)
• 4. Ability to answer questions and follow commands via neurocognitive testing
• 5. Estimated life expectancy greater than 6 months
• 6. Pathologic confirmation of extracerebral tumor site (eg, lung, breast, prostate) from either the primary site or a metastatic lesion
• 7. Willingness/Ability to undergo brain MRI scans
• 8. Able to give informed consent

Exclusion Criteria:

• 1. Pregnant or nursing women
• 2. Women of childbearing potential unwilling to use adequate contraception
• 3. Inability to complete a magnetic resonance imaging scan with contrast
• 4. Tumor directly invading the critical area to be spared (for example a patient with tumor invading a critical white matter tract; ineligible for cognitive-sparing)
• 5. Planned chemotherapy during SRS (on the day of SRS)
• 6. Previous whole brain radiation therapy
• 7. Leptomeningeal metastases (ineligible for SRS)
• 8. Metastases from primary germ cell tumor, small cell carcinoma, or primary CNS lymphoma (ineligible for SRS)