PRIOR CONCURRENT THERAPY: Recovered from toxic effects of prior therapy Biologic therapy: See Disease Characteristics No concurrent interferon Chemotherapy: See Disease Characteristics No prior purine nucleoside analogues (e.g., fludarabine, pentostatin, or 2- chlorodeoxyadenosine) At least 3 weeks since prior chemotherapy (6 weeks since nitrosoureas) No other concurrent cytotoxic chemotherapy Endocrine therapy: No prior octreotide for lymphoma No concurrent corticosteriods except for Addison's disease Radiotherapy: Not specified Surgery: Not specified Other: No other concurrent investigational drugs