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

Participants may be newly diagnosed small cell lung cancer with brain metastases at initial staging, or can alternatively be patients who develop brain metastases on therapy or during surveillance of systemic disease.

All participants will undergo MSK standard SRS. A CT simulation will be performed per institutional standards, typically with contrast unless a contraindication exists. A contrast-enhanced MRI with 1mm slices will be fused to the CT simulation scan for the purposes of SRS planning. The SRS GTV will be considered the visible tumor on MRI and CT contrast enhanced studies. An expansion of 1-2mm will be used to create the PTV. Radiation dose may be between 16Gy and 30Gy in 1 to 5 fractions, per the discretion of the treating radiation oncologist. Participants with multiple lesions may receive different doses to each lesion per the discretion of the treating radiation oncologist. Concurrent treatment to other body sites is permitted.

All participants will undergo lumbar puncture for CSF collection at study enrollment.. Lumbar punctures will be performed by clinical staff in neurology or neuroradiology, per the discretion of the treating radiation oncologist, as dictated by scheduling limitations and expected clinical difficulty in obtaining a sample (e.g. requiring fluoroscopic guidance), with input from the PI, neurology, and/or neuroradiology as necessary. Participants will be encouraged to undergo repeat lumbar puncture for CSF collection at 3 months (+/- 4 weeks), and at the time of CNS disease progression, though these latter timepoints are not required. CSF cytology will be evaluated.