Plerixafor

Author's disclosures of potential conflicts of interest are found at the end of this article. S ince the early 1980s, high-dose chemotherapy followed by autologous hematopoi-etic stem cell transplantation (HSCT) has emerged as standard therapy for patients with hematologic ma-lignancies, including non-Hodgkin lymphoma (NHL) and multiple myelo-ma (MM). In 2009, 32,000 autologous transplants were performed worldwide , 12,000 of which were completed in centers across the United States. Peripheral blood stem cells (PBSCs) were the source of hematopoietic stem cells (HSCs) in 98% of the patients who had undergone transplant (Pasquini & Wang, 2010). Initially, HSCs were harvested from the recipient's bone marrow, subjecting the patient to the risks of anesthesia , musculoskeletal discomfort and damage, and blood loss. A shift toward mobilization, or movement, of stem cells from the bone marrow to the peripheral blood and collection of HSCs from the peripheral blood occurred after early studies showed more rapid engraftment after high-dose che-motherapy with peripheral blood stem cell products compared with bone marrow products. As a consequence, the overall period of cytopenia was decreased with concomitant reduction in the need for supportive measures such as blood and platelet transfusions and antibiotic therapy (Bensinger et al., 2001). Over the past decade, mobilization and collection of PBSCs has become standard practice for patients undergoing autologous transplants. Commonly, stem cells are mobilized from the bone marrow micro-environment to the peripheral blood using either chemotherapy plus high-dose granulocyte colony-stimulating factor (G-CSF; filgrastim [Neupogen]) or high-dose G-CSF alone. US Food and Drug Administration (FDA) guidelines for G-CSF mobilization define a dosage at 10 μg/kg/day although institutional variations exist. Leukophere-sis begins either on recovery of counts postchemotherapy or on day 4 or 5 of G-CSF therapy alone, a time generally associated with the peak migration of HSCs as determined by flow cytomet-ric analysis of the surface expression of the CD34 antigen on peripheral blood mononuclear cells. Daily subcu-taneous G-CSF injections and collections continue until the target number of CD34+ HSCs has been collected. Chemotherapy mobilization results in higher CD34+ cell collections; however, this can be offset by the risk of higher toxicity leading to increased rates of hospitalization for neutropenic fever and infection (Meldgaard Knud