Haema 2013; 4(3):210-219
by Panagiotis Tsirigotis1, Konstantinos Girkas2
1Associate Professor of Haematology, 2nd Department of Internal Medicine, Medical School, University of Athens, “ATTIKO” General Hospital, Athens,
2Consultant in Hematology, 2nd Department of Internal Medicine, Medical School, University of Athens, “ATTIKO” General Hospital, Athens, Greece
Abstract
Hematopoietic stem cells and committed progenitors recirculate constantly between peripheral blood and bone marrow compartments. The number of immature precursors in peripheral blood is very low under steady state conditions. However, under certain circumstances like post priming with granulocyte colony stimulating factor (G-CSF), or during hematopoietic recovery after chemotherapy, large numbers of hematopoietic precursors are mobilized in peripheral blood. Mobilized hematopoietic stem cells can rescue an animal if reinfused after fully myeloablative conditioning. During the last decades, mobilized peripheral blood stem cells (PBSC)s have been increasingly used as a source of stem cells and currently have totally replaced bone marrow grafts in the setting of autologous stem cell transplantation (auto-SCT). G-CSF with or without previous administration of chemotherapy is used for PBSC mobilization. PBSC adequacy is monitored with CD34+ cell enumeration using flow cytometry. The optimal CD34+ cell dose has been set at 5×106/kg, while auto-SCT should be better avoided if PBSC graft contains less than 2×106/kg CD34+ cells. However, a significant percentage of patients, as well as normal donors fail to mobilize sufficient amounts of CD34+ cells using conventional methods. These patients are characterized as poor mobilizers and treating them is a major challenge. Plerixafor, a novel CXCR4 antagonist, has been recently approved for PBSC mobilization and is effective in 70% of patients who failed G-CSF mobilization. Early identification of poor mobilizers and immediate salvage administration of plerixafor in case of insufficient mobilization is reasonable, and might actually help in saving costs and time.