PRIOR CONCURRENT THERAPY: Biologic therapy: No prior Leuvectin. Chemotherapy: At least 3 weeks since prior chemotherapy (6 weeks for mitomycin or hydroxyurea). Endocrine therapy: No prior hormonal therapy for prostate cancer. Radiotherapy: See Disease Characteristics. At least 3 weeks since prior radiotherapy. Surgery: At least 1 month since prior intrathoracic or intra-abdominal surgery. At least 2 weeks since other prior major surgery. Other: At least 10 days since prior anticoagulants or non-steroidal anti-inflammatory agents. No neoadjuvant or other concurrent anticancer drug therapy. No concurrent immunosuppressive drugs. No other concurrent experimental therapy.