Retrospective study of alemtuzumab vs ATG-based conditioning without irradiation for unrelated and matched sibling donor transplants in acquired severe aplastic anemia: a study from the British Society for Blood and Marrow Transplantation

This retrospective national studycompared the use of alemtuzumab- based conditioning regimensfor hematopoietic SCT (HSCT) in acquired severe aplastic anemiawith antithymocyte globulin (ATG)-based regimens. One hundred patients received alemtuzumaband 55 ATG-based regimens. A matched sibling donor (MSD) was used in 87 (56%), matched unrelated donor (MUD) in 60 (39%) and other related or mismatched unrelated donor (UD) in 8 (5%) patients. Engraftment failure occurred in 9% of the alemtuzumabgroup and 11% of the ATG group. Five-year OS was 90% for the alemtuzumaband 79% for the ATG groups, P=0.11. For UD HSCT, OS of patients was better when using alemtuzumab(88%) compared with ATG (57%), P=0.026, although smaller numbers of patients received ATG. Similar outcomes for MSD HSCT using alemtuzumabor ATG were seen (91% vs 85%, respectively, P=0.562). A lower riskof chronic GVHD (cGVHD) was observed in the alemtuzumabgroup (11% vs 26%, P=0.031). On multivariate analysis, use of BM as stem cell source was associated with better OS and EFS, and less acute and cGVHD; young age was associated with better EFS and lower riskof graft failure. This large study confirms successful avoidance of irradiation in the conditioning regimensfor MUD HSCT patients.