PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since biologic therapy Chemotherapy: At least 8 weeks since nitrosoureas (e.g., lomustine, carmustine, mitomycin) At least 4 weeks since any other chemotherapy Recovered from all toxic effects No concurrent chemotherapy Endocrine therapy: At least 4 weeks since endocrine therapy No concurrent hormonal therapy Radiotherapy: At least 4 weeks since radiotherapy No prior irradiation of more than 25% of the marrow Surgery: Not specified Other: No concurrent nonsteroidal antiinflammatory agents or aspirin