Bone marrow engraftment following unrelated donor transplantation utilizing busulfan and cyclophosphamide preparatory chemotherapy.

Two major problems of unrelated donor transplantation have been an increased incidence of GVHD and graft failure. Even with HLA identity by microlymphocytotoxicity assay and non-reactive MLC, URD marrow transplant recipients have a higher incidence of graft rejection and GVHD. The preparative regimen busulfan 16 mg/kg and cyclophosphamide 120 mg/kg (BuCy2) has been shown to be at least as effective in preparation of recipients with CML of HLA-identical sibling grafts as cyclophosphamide and total body irradiation (Cy/TBI). However, concern about a high rejection rate in URD transplants has prevented most centers from using BuCy2 in this setting. From March 1990 to March 1994, 26 patients underwent URD transplantation following preparation with BuCy2. Patients received either standard cyclosporine and methotrexate or cyclosporine and methylprednisolone for GVHD prophylaxis. Two patients died on day 16 and 20 without evidence of hematopoietic engraftment. Of the 24 patients evaluable for engraftment, 23 (96%) had evidence of donor engraftment defined as an ANC > 0.5 x 10(9)/1. No patient who had initial engraftment had late graft failure. Within our study group the risk of graft rejection or graft failure does not appear to be higher than that reported for URD transplants utilizing TBI-containing regimens.