Abstract
Anti-thymocyte globulin (ATG) has been introduced in preventing acute graft-versus-host disease (AGvHD) in several studies. Many of them suggest that ATG at a total dose range of 4.5∼15 mg/kg reduces the risk of severe AGvHD but increases the risk of infections. We tried to investigate the role of ATG in HLA-mismatched unrelated hematopoietic stem cell transplantations (uHSCT), specifically in patients who received G-CSF mobilized peripheral blood stem cells (PBSCs) or from allele(s)/antigen mismatched unrelated donors from worldwide donor registries. Sixty five patients with intermediate to unfavourable risk AML who received HLA-mismatched uHSCT from the available Asian as well as Caucasian donors were enrolled. We compared 2 different groups according to the use of ATG (group 1) or not (group 2). The addition of ATG (thymoglobulin, Genzyme), at a dose of 1.25 mg per kilogram of body weight per day for 2 consecutive days, for recipients who received either PBSCs and/or from mismatched unrelated donors (group 1, N = 35); this was added to prevent the development of AGvHD together with our standard regimen which consisted of methotrexate (10 mg/m2 intravenously bolus on day +1; and methotrexate 5 mg/m2 intravenously bolus, on days +3, +6, +11) and tacrolimus starting at day –1. G-CSF was administered in all patients at a dose of 5 mg/kg subcutaneously per day from D + 7 after transplantation until neutrophil recovery. The median age was 38 (range, 16–65) and the median follow-up duration was 24 months (range, 3–72). The majority of patients had intermediate or unfavourable cytogenetic features. The main conditioning regimen consisted in cyclophosphamide plus total body irradiation. The transplanted patients were all successfully engrafted. The median time to neutrophil (>0.5 × 109/kg) and platelet (>20 × 109/kg) recovery was 15 vs 17 days, 14 vs 17 days in the group 1 and 2, respectively. The overall incidence of AGvHD and chronic GvHD was 38% and 41%; 33% and 35%, 37% and 48% for patients with group 1 and group2, respectively. Nine (14%) patients were relapsed so far. The comparison of estimated probability of disease-free survival rate at 2-year for each group was 89% vs 74%, respectively. The estimated probability of event-free survival rate at 2-year was 65% vs 51%, respectively. The overall 2-year non-relapse TRM was 14%. These results suggest that the uHSCT performed with a very low dose of ATG (total 2.5 mg/kg) are feasible with a promising outcome.
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