Topotecan in Treating Young Patients With Neoplastic Meningitis Due to Leukemia, Lymphoma, or Solid Tumors

DISEASE CHARACTERISTICS: * Diagnosis of neoplastic meningitis secondary to leukemia, lymphoma (including AIDS-related lymphoma), or solid tumor (including primary CNS tumors or carcinomas of unknown primary site), defined by 1 of the following criteria: * Cerebral spinal fluid (CSF) cell count \> 5/μL AND evidence of blast cells on cytospin or by cytology (for patients with leukemia or lymphoma) * Presence of tumor cells on cytospin or cytology OR unequivocal presence of meningeal disease by MRI (for patients with solid tumor) * No conventional therapy for neoplastic meningitis exists * Patients with CNS leukemia or lymphoma must be refractory to conventional therapy, including radiotherapy (i.e., second or greater relapse) * Patients with CNS leukemia or lymphoma must have had a negative bone marrow aspiration within the past 2 weeks * No clinical evidence of obstructive hydrocephalus * No compartmentalization of CSF flow by radioisotope indium In 111 or technetium Tc 99 DTPA flow study * No ventriculoperitoneal or ventriculoatrial shunt unless patient is completely shunt-independent * No impending spinal cord compression or other CNS involvement (e.g., acute visual loss secondary to optic nerve involvement) requiring emergent local radiotherapy PATIENT CHARACTERISTICS: Age * 3 to 21 Performance status * Lansky 60-100% (≤ 16 years of age) OR * Karnofsky 60-100% (\> 16 years of age) Life expectancy * Not specified Hematopoietic * Not specified Hepatic * No…