Hippocampal Avoidance in Craniospinal Irradiation for the Treatment of Leptomeningeal Metastases From Breast Cancer or Non-small Cell Lung Cancer

This phase II clinical trial studies how well craniospinal irradiation (CSI) with hippocampal avoidance, using proton therapy or volumetric modulated arc therapy (VMAT), works in treating patients with breast cancer or non-small cell lung cancer (NSCLC) that has spread from the original (primary) tumor to the cerebrospinal fluid (CSF) and meninges (thin layers of tissue that cover and protect the brain and spinal cord) (leptomeningeal metastases). Radiation therapy is an effective treatment in relieving localized symptoms caused by leptomeningeal metastases. However, the type of radiation therapy typically used does not prevent the spread of leptomeningeal disease. CSI (radiation therapy directed at the brain and spinal cord to kill tumor cells) may be able to target all of the areas of possible leptomeningeal tumor spread. CSI may however result in significant neurological side effects due to radiation damage to a part of the brain called the hippocampus. Hippocampal avoidance (HA) reduces the amount of radiation to the hippocampus. Proton or VMAT CSI with HA may be an effective treatment while reducing neurological side effects for patients with leptomeningeal metastases from breast cancer and NSCLC.