Testing if High Dose Radiation Only to the Sites of Brain Cancer Compared to Whole Brain Radiation That Avoids the Hippocampus is Better at Preventing Loss of Memory and Thinking Ability

This phase III trial compares the effect of stereotactic radiosurgery to standard of care memantine and whole brain radiation therapy that avoids the hippocampus (the memory zone of the brain) for the treatment of small cell lung cancer that has spread to the brain. Stereotactic radiosurgery is a specialized radiation therapy that delivers a single, high dose of radiation directly to the tumor and may cause less damage to normal tissue. Whole brain radiation therapy delivers a low dose of radiation to the entire brain including the normal brain tissue. Hippocampal avoidance during whole-brain radiation therapy (HA-WBRT) decreases the amount of radiation that is delivered to the hippocampus which is a brain structure that is important for memory. The drug, memantine, is also often given with whole brain radiotherapy because it may decrease the risk of side effects related to thinking and memory. Stereotactic radiosurgery may decrease side effects related to memory and thinking compared to standard of care HA-WBRT plus memantine.