A Study of Stereotactic Radiosurgery (SRS) for People With Lung Cancer That Has Spread to the Brain

Inclusion Criteria: * Histologic diagnosis of small cell lung cancer * Radiographic diagnosis of up to 20 brain metastases on contrast-enhanced MRI * Age 18 and above * Performance status KPS 60-100/ECOG 0-2 * Female patients must be of non-reproductive potential or have a negative serum pregnancy test at the time of enrollment * The patient or legally authorized representative is able to provide informed consent Exclusion Criteria: * Unable to undergo contrast-enhanced MRI brain * Leptomeningeal disease confirmed on lumbar puncture, MRI brain, or MRI spine * Pregnant or lactating women * Prior brain-directed radiotherapy * Uncontrolled systemic disease without reasonable systemic therapy options felt likely to result in death as observed on CT or PET/CT imaging, no more than 3 months before study enrollment