Topotecan in Treating Patients With Recurrent, Progressive, or Refractory Cancer That is Metastatic to the Lining Around the Brain

DISEASE CHARACTERISTICS: * Histologic or tumor marker confirmation of malignancy at original diagnosis * Neoplastic meningitis/leptomeningeal metastasis refractory to conventional therapy and other therapies of higher priority, defined as: * Stratum A: * Small non-cleaved lymphoma (Burkitt's) with any L-3 blast in cerebrospinal fluid (CSF) * Any other lymphoma or leukemia with CSF cell count greater than 5/mm3 AND evidence of blast cells by cytology or cytospin preparation OR * Stratum B: * Solid tumor or other malignancy with presence of tumor cells on cytospin OR positive cytology OR neuroimaging evidence of leptomeningeal tumor by MRI or CT myelogram * No leptomeningeal leukemia or lymphoma with concurrent bone marrow relapse * No clinical evidence of untreated obstructive hydrocephalus or compartmentalization of the CSF PATIENT CHARACTERISTICS: Age: * 65 and under Performance status: * Lansky 50-100% (age 16 and under) * Karnofsky 50-100% OR ECOG 0-3 (over age 16) Life expectancy: * At least 2 months Hematopoietic: * Stratum B: * Absolute neutrophil count at least 750/mm\^3 * Platelet count at least 75,000/mm\^3 (transfusion independent) * Hemoglobin at least 10.0 g/dL (red blood cell transfusions allowed) Hepatic: * Bilirubin no greater than 1.5 times normal * SGOT or SGPT less than 2.5 times upper limit of normal Renal: * Creatinine no greater than 1.5 mg/dL OR * Creatinine clearance or radioisotope glomerular filtration rate at least 70 mL/min Neurologic: * Seizures allowed if well controlled and on anticonvulsants * CNS toxicity no greater than grade 2 Other: * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * No uncontrolled infections * HIV allowed PRIOR CONCURRENT THERAPY: Biologic therapy: * No concurrent immunomodulating agents (stratum B) * No stem cell transplantation (stratum A) Chemotherapy: * At least 2 weeks since prior chemotherapy (4 weeks for nitrosoureas) * No other concurrent cancer chemotherapy (stratum B) * Other concurrent systemic cancer chemotherapy for leukemia or lymphoma allowed with the following restrictions: * No oral or IV topotecan * No moderate or high-dose IV or subcutaneous cytarabine (greater than 1.0 g/m2 per day) * No moderate or high-dose IV methotrexate (greater than 1 g/m2 per day) * No IV thiotepa * No myeloablative chemotherapy * No intrathecal or intraventricular chemotherapy Endocrine therapy: * Concurrent corticosteroids allowed only for treatment of increased intracranial pressure in patients with CNS tumors * No concurrent intrathecal or intraventricular hydrocortisone Radiotherapy: * At least 4 weeks since completion of radiotherapy to the brain or spine and recovered * Concurrent radiotherapy to localized painful lesions producing acute neurologic dysfunction allowed provided at least 1 measurable lesion is not irradiated * No concurrent craniospinal or whole-brain radiotherapy Surgery: * Not specified Other: * Recovered from prior therapy * At least 7 days since prior investigational drug * No other concurrent intrathecal or intraventricular therapy for leptomeningeal disease