PRIOR CONCURRENT THERAPY: Biologic therapy: See Disease Characteristics At least 2 months since prior biologic therapy (e.g., hematopoietic growth factors or biological response modifiers) Chemotherapy: See Disease Characteristics At least 2 months since prior chemotherapy Endocrine therapy: At least 2 months since prior endocrine therapy Radiotherapy: At least 2 months since prior radiotherapy Concurrent radiotherapy allowed Surgery: At least 2 months since prior surgery Other: No other concurrent investigational drugs