Low incidence of transplantation-related acute complications in patients with chronic myeloid leukemia undergoing allogeneic stem cell transplantation with a low-dose (550 cGy) total body irradiation conditioning regimen

Although allogeneic transplantation is a curative therapy for chronic myelo id leukemia (CML), treatment-related mortality is still a major cause of po sttransplantation mortality, especially for patients older than 40 years. W e investigated, in a phase II trial, the role of a low-dose (550 cGy) high- dose rate (35 cGy/min) single-exposure total body irradiation (TBI) conditi oning regimen for allogeneic peripheral blood stem cell (PBSC) transplantat ion in patients with CML. Between June 1997 and August 2000, 30 adult patie nts with CML underwent cytokine-mobilized allogeneic PBSC transplantation f rom HLA-matched siblings following administration of cyclophosphamide (60 m g/kg per day intravenously on days -2 and -1) and single-dose TBI (550 cGy delivered at 30 cGy/min on day 0). Cyclosporine A alone was administered fo r prophylaxis against graft-versus-host disease (GVHD). Median patient age was 47 years (range, 21-63 years), with 23 patients (77%) older than 40 yea rs. The preparative regimen was well tolerated. Grade 4 toxicities and oral mucositis were not observed. Graft failure did not occur. Severe acute GVH D was observed in 5 patients (17%). The median follow-up was 23 months (ran ge, 6-39 months). Cytogenetic or hematologic relapse was detected in 3 pati ents (10%), 2 of whom subsequently entered remission following a taper of i mmunosuppression. Nonrelapse mortality occurred in 5 patients (17%), and th e Kaplan-Meier estimate of survival at 2 years was 83% (95% confidence inte rval, 70%-97%). In summary, this low-dose TBI-based preparative regimen res ulted in uniform donor engraftment, with markedly reduced organ toxicity an d nonrelapse mortality, in this relatively older cohort of patients with CM L.