The impact of in vivo T-cell depletion on transplantation outcomes in patients transplanted with reduced-intensity conditioning (RIC) remains controversial. This study assessed the outcome of 1250 adult patients with de novo AML in first CR (CR1) given PBSC from HLA-identical siblings after chemotherapy-based RIC. A total of 554 patients did not receive any form of in vivo T-cell depletion (control group), whereas antithymocyte globulin (ATG) and alemtuzumab were given in 444 and 252 patients, respectively. The incidences of grade II-IV acute GVHD were 21.4, 17.6 and 10.2% in control, ATG and alemtuzumab patients, respectively (Po0.001).In multivariate analysis, the use of ATG and the use of alemtuzumab were each associated with a lower risk of chronic GVHD (Po0.001 each), but a similar risk of relapse, and of nonrelapse mortality, and similar leukemia-free survival and OS. Further, among patients given BU-based RIC, the use of o6 mg/kg ATG did not increase the risk of relapse (hazard ratio, HR ¼ 1.1), whereas there was a suggestion for higher relapse risk in patients given X6 mg/kg ATG (HR ¼ 1.4, P ¼ 0.08). In summary, these data suggest that a certain amount of in vivo T-cell depletion can be safely used in the conditioning of AML patients in CR1 given PBSC after chemotherapy-based RIC.
INTRODUCTIONThe use of PBSC instead of BM in patients receiving grafts from HLA-matched donors after myeloablative conditioning has been associated with faster hematological recovery, lower relapse risk in patients with advanced disease (due to higher immune-mediated graft-versus-tumor (GVT) effects), but also higher incidence extensive chronic GVHD. 1-4 These observations prompted several groups of investigators to study in vivo T-cell depletion of the graft with antithymocyte globulin (ATG) or alemtuzumab as a way to reduce severe GVHD in patients given PBSC after highdose myeloablative conditioning regimen. [5][6][7] These studies demonstrated that the use of ATG or alemtuzumab was successful at preventing severe GVHD without apparently increasing the relapse incidence (RI). [5][6][7] In contrast to patients given grafts after myeloablative conditioning who benefit from both the high-dose chemo/radiotherapy given as part of the conditioning regimen and the GVT effect for tumor eradication,