Feasibility of reduced intensity hematopoietic stem cell transplantation from an HLA-matched unrelated donor

To evaluate the feasibility of reduced intensity stem cell transplantation ( RIST) with bone marrow from a matched unrelated donor ( MUD), we retrospectively investigated 20 patients with hematological disorders who received RIST in the Tokyo SCT consortium from January 2000 to October 2002. The preparative regimens were. udarabine-based ( 150 - 180 mg/m(2), n = 18) or cladribine- based ( 0.77 mg/kg, n = 2). To enhance engraftment, antithymocyte globulin ( ATG) a nd 4 or 8Gy total body irradiation ( TBI) were added to these regimens in nine and 11 patients, respectively. GVHD prophylaxis was cyclosporine with or without methotrexate. In all, 19 achieved primary engraftment. Three developed graft failure ( one primary, two secondary), and five died of treatment-related mortality within 100 days of transplant. Seven of the 19 patients who achieved initial engraftment developed grade II - IV acute GVHD, and seven of 13 patients who survived 4100 days developed chronic GVHD. At a median follow- up of 5.5 months, estimated 1- year overall survival was 35%. Compared with a TBI- containing regimen, an ATG- containing regimen was associated with a high risk of graft failure ( 30 vs 0%, P = 0.0737). This study supports the feasibility of RIST from MUD; however, procedure- related toxicities remain signi. cant in its application to patients.