PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent biologic therapy Chemotherapy: See Disease Characteristics No more than 2 prior chemotherapy regimens for metastatic disease One prior adjuvant chemotherapy regimen for metastatic disease allowed At least 4 weeks since prior chemotherapy No other concurrent chemotherapy Endocrine therapy: One prior regimen of hormonal therapy for metastatic disease allowed At least 3 weeks since prior hormonal therapy and recovered No concurrent hormonal or corticosteroid therapy Radiotherapy: At least 4 weeks since prior radiotherapy to less than 25% bone marrow No concurrent radiotherapy Surgery: At least 4 weeks since prior surgery and recovered No concurrent surgery Other: At least 4 weeks since any prior treatment directed at the tumor and recovered No other concurrent anticancer or investigational therapy No concurrent participation on another therapeutic clinical trial