PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: Concurrent chemotherapy allowed Endocrine therapy: Not specified Radiotherapy: Not specified Surgery: At least 1 month since prior eye, spinal cord, or CNS surgery Other: At least 1 day since prior heparin or enoxaparin At least 1 week since prior therapeutic coumadin (prior prophylactic coumadin allowed) No other concurrent anticoagulants