Proton Craniospinal Radiation Therapy vs. Partial Photon Radiation Therapy for Leptomeningeal Metastasis From Solid Tumors

The investigators are doing this study to find out whether proton craniospinal radiation therapy (proton CSI) or partial photon radiation therapy is more effective at preventing leptomeningeal metastasis from worsening. The proton CSI targets the entire space containing the CSF, brain, and spinal fluid. The partial photon radiation therapy treats only areas where the patient is having symptoms, such as the entire brain or part of the spine. The investigators also want to find out if proton CSI improves the symptoms patients may be experiencing because of the leptomeningeal metastasis. In addition, the investigators will compare the side effects of proton CSI and partial photon therapy. Patients undergoing proton beam RT will receive their treatment at the New York Proton Center in New York, NY. As part of the New York Proton Consortium, MSK has contracted for its faculty to treat patients at the New York Proton Center. If it is unfeasible for patients to get treated at NYPC, patients will have the decision to get treated at ProCure in Summerset, NJ.