Peripheral blood stem cell versus bone marrow transplantation: A perspective from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation.

Over the past decade, transplantation of peripheral blood hematopoietic cells has increased and is now the predominant graft source for related or unrelated adult allogeneic hematopoietic stem cell transplantation. At the same time, increasing numbers of patients are receiving reduced-intensity conditioning (RIC) prior to hematopoietic stem cell infusion. In prior work using smaller patient numbers and limited data, RIC peripheral blood stem cell (PBSC) transplantation was shown to be noninferior to RIC bone marrow (BM) transplantation for acute leukemia. A recent, large registry analysis from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation showed that peripheral blood grafts result in superior outcomes compared with BM after RIC regimens for acute leukemia. The T-cell-replete PBSC allografts are associated with significant graft-versus-leukemia (GVL) benefits that are important drivers of improved leukemia-free survival and overall survival. However, an increased risk of chronic graft-versus-host disease (cGVHD) after peripheral blood grafts is concerning and long-term follow-up comparing peripheral versus BM grafts after RIC regimens is needed. Further assessment of the long-standing risks should be undertaken in an effort to better understand whether the risk of cGVHD among peripheral blood graft recipients translates into continued GVL effects and long-term remissions and cures or if it results in late morbidity and mortality.