Transplant of hematopoietic stem cells in childhood: where we are and where we are going.

Over the past decade, relevant improvements and refinements have significantly changed the indications, technique and results obtained with allogeneic transplantation of hematopoietic stem cells (HSC) in childhood. In this review the most important innovations that have characterized the practice of HSC transplantation in childhood during this decade will be discussed. We will analyze the clinical and biological advantages or disadvantages which characterize most typically HSC transplantation procedure in terms of the source of these cells (bone marrow, peripheral blood, placental blood). A fundamental turning point in the history of allogeneic transplantation of HSC is represented by the use of placental blood, which was first employed in 1988. Autologous, peripheral blood progenitor cells are increasingly being used as a source of HSC following high-dose therapy for malignant disease, because of the ease of collection and the markedly faster kinetics of engraftment in comparison with bone marrow. In particular, over the past decade, due to the much faster recovery of all hematopoietic lineages in comparison with bone marrow and due to the short duration of antibiotic therapy and hospitalization, also in pediatric patients, auto-transfusion of circulating hematopoietic progenitors is rapidly replacing autologous bone marrow transplantation after high-dose chemotherapy for lymphomas and solid tumors. On the contrary, due to concerns in pediatric patients related to the use of hematopoietic growth factors in a healthy donor, allograft of peripheral blood progenitor cells is not routinely used. Since indications for allogeneic HSC transplantation that had already been well established in the recent past have been complemented by others and a relevant number of disorders are no longer considered to be eligible for allograft, the evolution in the indications for allogeneic transplant of HSC in childhood will be discussed. Likewise, biotechnological, social and organizational refinements which have allowed the greatest advances of allogeneic HSC transplantation in this decade will be analyzed, as well as some still open bioethical question regarding this procedure.