PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent immunotherapy Chemotherapy: See Disease Characteristics At least 2 weeks since prior gemcitabine and recovered No prior chemotherapy except gemcitabine No other concurrent chemotherapy Endocrine therapy: No concurrent corticosteroids or hormones Radiotherapy: No concurrent radiotherapy Surgery: At least 2 weeks since prior major surgery No major surgery within 8 weeks following initiation of study treatment