Exatecan Mesylate in Treating Children With Relapsed or Refractory Rhabdomyosarcoma

DISEASE CHARACTERISTICS: * Histologically confirmed recurrent or resistant rhabdomyosarcoma * Measurable disease * The following are not considered measurable disease: * Ascites * Pleural effusion * Lytic bone lesions * No symptomatic brain metastases PATIENT CHARACTERISTICS: Age * Any age Performance status * ECOG 0-2 (over 10 years old) * Lansky 60-100% (10 years old and under) Life expectancy * At least 12 weeks Hematopoietic * Absolute neutrophil count at least 750/mm\^3 * Platelet count at least 75,000/mm\^3 * Hemoglobin at least 8.5 g/dL Hepatic * Bilirubin no greater than 2.0 mg/dL * Albumin at least 2.8 g/dL * AST or ALT no greater than 2.5 times upper limit of normal (ULN) (5 times ULN if liver metastases present) Renal * Creatinine no greater than 1.5 times ULN Other * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * No life threatening illness (unrelated to tumor) within the past 6 months * No other malignancy within the past 5 years except nonmelanoma skin cancer or carcinoma in situ of the cervix * No concurrent active serious infection * No concurrent uncontrolled infection * No overt psychosis or other incompetency that would preclude study compliance or giving informed consent * No other concurrent noncancer-related illness that would preclude study participation or follow-up PRIOR CONCURRENT THERAPY: Biologic therapy * At least 3 months since prior autologous bone marrow or stem cell transplantation * No concurrent anticancer biologic therapy Chemotherapy * Recovered from prior adjuvant or systemic chemotherapy * Prior topoisomerase I inhibitor therapy allowed * No other concurrent anticancer chemotherapy Endocrine therapy * Not specified Radiotherapy * More than 4 weeks since prior extensive radiotherapy to the cranial-spinal axis, whole pelvis, or 25% of marrow reserve * No concurrent anticancer radiotherapy Surgery * At least 4 weeks since prior major surgery * Recovered from prior surgery * No concurrent anticancer surgery Other * At least 28 days since prior investigational drugs (including analgesics or antiemetics) * No more than 2 prior regimens for rhabdomyosarcoma * No concurrent grapefruit-containing beverages or foods * No other concurrent investigational drugs during and for 28 days after final dose of study drug