Exatecan Mesylate in Treating Patients With Advanced Soft Tissue Sarcoma

DISEASE CHARACTERISTICS: * Histologically confirmed soft tissue sarcoma * Malignant fibrous histiocytoma * Liposarcoma * Rhabdomyosarcoma * Synovial sarcoma * Malignant paraganglioma * Fibrosarcoma * Leiomyosarcoma * Angiosarcoma including hemangiopericytoma * Malignant peripheral nerve sheath tumor * Unclassified sarcoma * Miscellaneous sarcoma including mixed mesodermal tumors of the uterus * The following tumor types are excluded: * Gastrointestinal stromal tumor * Chondrosarcoma * Malignant mesothelioma * Neuroblastoma * Osteosarcoma * Ewing's sarcoma * Embryonal rhabdomyosarcoma * Prior chemotherapy for metastatic disease required * One line of combination chemotherapy containing anthracycline OR * No more than 2 single-agent regimens including anthracycline * Adjuvant chemotherapy not considered first line unless tumor progresses within 6 months after treatment * Must have 1 measurable lesion * Clinical evidence of progression within 6 weeks prior to study * Osseous lesions and pleural effusions not considered measurable * No known or symptomatic CNS metastases PATIENT CHARACTERISTICS: Age: * 15 to 75 Performance status: * WHO 0-1 Life expectancy: * Not specified Hematopoietic: * WBC at least 4,000/mm\^3 * Platelet count at least 100,000/mm\^3 Hepatic: * Bilirubin no greater than 1.8 mg/dL * Albumin at least 2.5 g/dL Renal: * Creatinine no greater than 1.4 mg/dL OR * Creatinine clearance greater than 65 mL/min Cardiovascular: * No history of severe cardiovascular disease Other: * Not pregnant * Negative pregnancy test * Fertile patients must use effective contraception during and for up to 6 months after study participation * No other severe medical illness, including psychosis * No other prior or concurrent malignancy except adequately treated basal cell skin cancer or carcinoma in situ of the cervix PRIOR CONCURRENT THERAPY: Biologic therapy: * Not specified Chemotherapy: * See Disease Characteristics * More than 4 weeks since prior chemotherapy * No other concurrent cytotoxic therapy Endocrine therapy: * Not specified Radiotherapy: * No radiotherapy to the sole measurable lesion * No concurrent radiotherapy Surgery: * Not specified Other: * No other investigational drugs for 28 days prior to, during, and for 28 days after completion of study drug * No other concurrent anticancer therapy