A Prospective Single Arm Phase II Exploratory Study on the Combination of Whole Brain Radiotherapy, Thiotepa Intrathecal Injection and Systemic Treatment of Primary Diseases in the Treatment of Solid Tumor Leptomeningeal Metastasis

This study is testing a combination of whole-brain radiation, a chemotherapy drug injected directly into the spinal fluid (thiotepa), and treatment for the original cancer in patients whose solid tumor cancer has spread to the lining of the brain and spinal cord (called leptomeningeal metastasis). **You may be eligible if...** - You are 18 or older with a solid tumor cancer that has spread to the brain/spinal membranes, diagnosed by established guidelines - You have already completed a specific whole-brain radiation treatment regimen - Your general health score (ECOG) is 2 or less - You have an expected survival of at least 3 months - Your organ and bone marrow function are adequate **You may NOT be eligible if...** - You have not yet received the required whole-brain radiation - Your general health is too poor to tolerate further treatment - You have severe organ dysfunction Talk to your doctor to see if this trial is right for you.