PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: See Disease Characteristics At least 4 weeks since prior chemotherapy No more than one prior regimen of chemotherapy No prior gemcitabine No prior CI-994 At least 4 weeks since prior maintenance or consolidation therapy (e.g., matrix metalloprotein inhibitors) Endocrine therapy: See Disease Characteristics Radiotherapy: See Disease Characteristics At least 4 weeks since prior radiotherapy to primary site Surgery: Not specified