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BACKGROUND: An appreciable proportion of patients in need of salvage high-dose chemotherapy (HDC) and autologous peripheral blood stem cell (PBSC) transplantation (PBSCT) fail to mobilize adequate numbers of hematopoietic progenitors, and plerixafor is applied for that purpose. Limited data exist on remobilization of PBSCs in patients who have relapsed after prior HDC + PBSCT. Herein, we report on consecutive patients that had undergone successful prior single or tandem HDC for a variety of malignant neoplasms in our institution, and later required re-mobilization of PBSCs in order to support further HDC cycles. PATIENTS AND METHODS: Plerixafor was administered in combination with granulocyte-colony stimulating factor alone, or after mobilizing chemotherapy. Five patients, 2 B-cell non-Hodgkin lymphomas, 1 multiple myeloma, 1 germ-cell tumor, and 1 Ewing sarcoma, having relapsed after prior HDC + PBSCT, were deemed candidates for further cycle(s) of PBSC-supported HDC. Plerixafor was applied in a "just-in-time" strategy after low CD34+ numbers were measured on the first day of anticipated hematopoietic stem cell collection (non-Hodgkin lymphoma, germ-cell tumor, and Ewing sarcoma), or pre-emptively in multiple myeloma. RESULTS: Successful collection of adequate PBSCs was achieved in all patients, from 1.8 to 3.8 × 106/kg after a median of 2 (range, 1-3) leukaphereses; 4 of 5 patients underwent subsequent HDC + PBSCT and engrafted after a median of 11 days (range, 9-55 days) and 25 days (range, 17-76 days) for neutrophils and platelets, respectively. CONCLUSION: Plerixafor proved effective to mobilize adequate numbers of PBSCs in individual patients with relapsed malignancies after prior single or tandem HDC + PBSCT. These PBSCs could establish sustained multi-lineage hematopoietic engraftment without any sequelae.

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Salvage high-dose chemotherapy (HDC) and autologous hematopoietic stem cell (HSC) transplantation represents a curative treatment option for patients with relapsed/refractory germ-cell tumors (GCTs). However, an appreciable proportion of these fail to mobilize adequate numbers of hematopoietic progenitors; thus, plerixafor is applied for that purpose. Limited data exist on remobilization of HSCs after previous autografting. Here, we report a unique case that had undergone successful previous tandem HDC for relapsed GCT, and 1 year later required remobilization of HSCs to support two further cycles of HDC after subsequent multiple relapses and refractoriness requiring various salvage regimens. Plerixafor in combination with granulocyte-colony stimulating factor showed its efficacy in mobilizing 6×10 CD34+/kg HSCs able to rescue two HDC cycles of carboplatin-etoposide, leading to stable hematopoietic engraftment. Plerixafor showed its potency to mobilize adequate numbers of HSCs in a patient with relapsed/refractory GCT after previous tandem HDC and autografting. The case is discussed in the context of HSC mobilization in patients who have undergone previous HDC and autografting and are deemed to have poor hematopoietic reserves, and a detailed literature review of this topic is provided.

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An appreciable percentage of patients with relapsed/refractory germ-cell tumors (GCTs), candidates for high-dose chemotherapy (HDC) and autologous hematopoietic cell transplantation (HCT), fail to mobilize adequate hematopoietic stem cells (HSCs) numbers with granulocyte colony-stimulating factor (G-CSF)±salvage chemotherapy. Plerixafor has shown a potential to mobilize adequate CD34+HSCs numbers in this context. Here, we applied plerixafor in combination with G-CSF after salvage chemotherapy in 'poor' mobilizers with relapsed/refractory GCTs for HDC+HCT. Patients with relapsed/refractory GCTs (n=10) received salvage paclitaxel-ifosfamide-cisplatin (TIP) chemotherapy+G-CSF to mobilize adequate HSCs to support HDC, mainly with two courses of high-dose thiotepa-etoposide-carboplatin (TEC). Patients failing to achieve the minimum collection threshold of 2.0×10/kg CD34+ cells, to support at least one cycle of HDC, were administered plerixafor before the anticipated HSC collection during subsequent cycle(s). Overall, seven patients mobilized adequate CD34+ cells (>5.0×10/kg) aiming to support two cycles of HDC. Three patients did not mobilize adequate numbers of CD34+ cells after previous G-CSF plus salvage TIP, and plerixafor was added in subsequent cycle(s). This led to a collection of adequate CD34+ cells, able to support HDC with TEC (1-2 cycles). Hematopoietic engraftment for neutrophils (absolute neutrophil count>500/µl) and platelets (platelet count>20 000/µl) with plerixafor-mobilized HSCs occurred after a median of 9 and 14 days, respectively. Salvage TIP+G-CSF leads to successful HSC mobilization in patients with less heavily pretreated GCTs, whereas the addition of plerixafor to G-CSF+TIP led to mobilization of adequate HSCs that supported autografting after one to two TEC cycles.

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