PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since prior immunotherapy No concurrent biologic therapy Chemotherapy: At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas, mitomycin, and doxorubicin HCl liposome) Prior taxanes allowed No more than 2 prior chemotherapy regimens in metastatic setting Prior adjuvant/neoadjuvant chemotherapy allowed No other concurrent chemotherapy Endocrine therapy: See Disease Characteristics No concurrent hormonal therapy (except hormone replacement therapy or medication to maintain castrate status) Radiotherapy: At least 4 weeks since prior radiotherapy No prior radiotherapy to greater than 25% of bone marrow No concurrent radiotherapy Surgery: No concurrent surgery Other: At least 4 weeks since other prior investigational agents No other concurrent experimental anticancer medications No other concurrent specific antitumor therapy