Chemotherapy in Treating Children With Recurrent or Refractory Sarcomas

DISEASE CHARACTERISTICS: * Histologically confirmed malignancy that is relapsed or refractory to conventional therapy at original diagnosis including: * Brain tumors * Gliomas or astrocytomas * Medulloblastomas or primitive neuroectodermal tumor (PNET) in CNS * (Brain tumor stratum closed to accrual effective 07/02/2001) * Sarcomas * Soft tissue sarcoma (undifferentiated sarcoma, embryonal or alveolar rhabdomyosarcoma (RMS), or non-RMS soft tissue sarcoma) * Osteosarcoma * Ewing's sarcoma/peripheral PNET tumors * Neuroblastoma * (Neuroblastoma stratum closed to accrual effective 07/02/2001) * Histology requirement waived for brain stem tumors (Brain tumor stratum closed to accrual effective 07/02/2001) * Measurable disease documented by clinical, radiographic, or histologic criteria * Lesions in previously irradiated fields may be used to assess tumor response if there has been evidence of subsequent tumor growth in those fields * No bone marrow metastases with granulocytopenia and/or thrombocytopenia PATIENT CHARACTERISTICS: Age: * 30 days to 21 years at diagnosis Performance status: * ECOG 0-2 Life expectancy: * More than 2 months Hematopoietic: * Absolute neutrophil count at least 1,000/mm3 * Hemoglobin at least 10.0 g/dL (may receive RBC transfusions) * Platelet count at least 100,000/mm3 (50,000/mm3 if post bone marrow transplantation) (transfusion independent) Hepatic: * Bilirubin no greater than 1.5 times normal * SGOT or SGPT less than 2.5 times normal Renal: * Creatinine no greater than 1.5 times normal OR * Creatinine clearance or radioisotope glomerular filtration rate at least 70 mL/min Neurologic: * No greater than grade 2 CNS toxicity OR * Stable CNS status for brain tumors (Brain tumor stratum closed to accrual effective 07/02/2001) * Seizure disorders allowed if well-controlled with anticonvulsants Other: * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: * At least 3 months since prior bone marrow transplantation and recovered * At least 2 weeks since prior cytokines and recovered * No concurrent filgrastim (G-CSF) or other cytokines * No concurrent immunomodulating agents Chemotherapy: * At least 2 weeks since prior chemotherapy (4 weeks for nitrosoureas) and recovered * No prior topotecan or other camptothecins * No other concurrent anticancer chemotherapy Endocrine therapy: * Concurrent corticosteroids for CNS tumors with increased intracranial pressure allowed (Brain tumor stratum closed to accrual effective 07/02/2001) Radiotherapy: * At least 2 months since prior craniospinal radiotherapy or radiotherapy to more than 50% of the bone marrow and recovered * Concurrent radiotherapy to localized painful lesions allowed provided that at least 1 measurable lesion is not irradiated Other: * Recovered from any other prior therapy