Trial of Differential Margins in Single Isocenter Radiosurgery of Brain Metastases

This study is testing whether using different radiation margin sizes when delivering stereotactic radiosurgery (a precise, high-dose radiation technique) to multiple brain metastases in a single session affects treatment outcomes and side effects. **You may be eligible if...** - You are 19 years or older (male or female) - You have been diagnosed with brain metastases (cancer that has spread to the brain) - Your brain metastases have not been treated before at the same location - You are able to have an MRI scan **You may NOT be eligible if...** - You are pregnant - You received cytotoxic chemotherapy within 3 days of treatment - You are taking certain targeted drugs (like BRAF inhibitors) within 24 hours of treatment - You are enrolled in another drug study within 14 days - You are only receiving radiation to a post-surgical cavity with no remaining visible tumor Talk to your doctor to see if this trial is right for you.