Phase 1 Intrathecal Topotecan for Neoplastic Meningitis

1. To find the optimal dose of topotecan that can safely be given directly into the spinal fluid (called intrathecal administration) of children whose cancer has spread to the lining of the brain and/or spinal cord. 2. To find out what effects (good and bad) topotecan has when given directly into the cerebrospinal fluid in children with neoplastic meningitis (cancer that has spread to the lining of the brain and spinal cord). * Cerebrospinal fluid is the fluid that circulates around the brain and spinal cord. 3. To determine if intrathecal topotecan is beneficial to patients. 4. To better understand how topotecan is handled by the body after intrathecal administration. 5. To evaluate the cerebrospinal fluid for signs (markers) of tumor spread.