Elimination of PTV Margins Based on MRI-guided Adaptive Stereotactic Radiotherapy for Non-small Cell Lung Cancer With Brain Metastasis

This study tests whether a highly precise form of radiation therapy guided by MRI — where treatment is adapted in real time to the tumor's exact location and shape — can allow doctors to reduce or eliminate the "safety margin" around brain tumors while still effectively treating non-small cell lung cancer that has spread to the brain. **You may be eligible if...** - You are between 18 and 75 years old - You have non-small cell lung cancer confirmed by biopsy or cytology - You have 1–10 brain metastases (cancer spots in the brain) visible on contrast MRI - Radiation to tumors outside the brain is allowed concurrently **You may NOT be eligible if...** - You have received prior whole-brain radiation therapy - You have more than 10 brain metastases - Your overall health status doesn't meet the study requirements Talk to your doctor to see if this trial is right for you.