PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent biologic therapy Chemotherapy: See Disease Characteristics No concurrent chemotherapy At least 4 weeks since prior chemotherapy (6 weeks since nitrosoureas) and recovered Endocrine therapy: Not specified Radiotherapy: See Disease Characteristics At least 3 months since prior radiotherapy and recovered Surgery: See Disease Characteristics Other: At least 4 weeks since prior use of medical device No concurrent investigational agents