PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No prior chemotherapy for metastatic disease No prior adjuvant chemotherapy containing topoisomerase I inhibitors At least 6 months since other prior adjuvant chemotherapy Endocrine therapy: Concurrent corticosteroids allowed Radiotherapy: See Disease Characteristics Surgery: Not specified Other: At least 4 weeks since other prior investigational drugs No other concurrent anticancer therapy