Proton Beam Craniospinal Irradiation

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.

This phase III trial compares proton craniospinal irradiation (pCSI) to involved-field radiation therapy (IFRT) for the treatment of breast or non-small cell lung cancer that has spread from where it first started to the cerebrospinal fluid filled space that surrounds the brain and spinal cord (leptomeningeal metastasis). Patients with leptomeningeal metastasis (LM) may develop multiple areas of nervous system (neurologic) impairment that can be life-threatening. Radiation therapy (RT) effectively relieves local symptoms due to LM. RT uses high energy radiography (x-rays), particles, or radioactive seeds to kill cancer cells and shrink tumors. IFRT is commonly used to treat symptoms of LM. IFRT is radiation treatment that uses x-rays to treat specific areas of LM and to relieve and/or prevent symptoms. pCSI uses protons that can be directed with more accuracy than x-rays which allows treatment of the entire central nervous system space containing the cerebrospinal fluid (CSF), brain, and spinal cord. The pCSI treatment could delay the worsening of LM. Giving pCSI may be better than IFRT in treating LM in patients with breast or non-small cell lung cancer.