Mobilization of peripheral blood stem cells with chemotherapy and recombinant human granulocyte colony-stimulating factor (rhG-CSF): a randomized evaluation of different doses of rhG-CSF

Stem cell mobilization in multiple myeloma: challenges, strategies, and current developments

Among hematological malignancies, multiple myeloma (MM) represents the leading indication of autologous hematopoietic stem cell transplantation (auto-HCT). Auto-HCT is predominantly performed with peripheral blood stem cells (PBSCs), and the mobilization and collection of PBSCs are essential steps for auto-HCT. Despite the improved success of conventional methods with the incorporation of novel agents for PBSC mobilization in MM, mobilization failure is still a concern. The current review comprehensively summarizes various mobilization strategies for mobilizing PBSCs in MM patients and the evolution of these strategies over time. Moreover, existing evidence substantiates that the mobilization regimen used may be an important determinant of graft content. However, limited data are available on the effects of graft characteristics in patient outcomes other than hematopoietic engraftment. In this review, we discussed the effect of graft characteristics on clinical outcomes, mobilization failure, factors predictive of poor mobilization, and potential mobilization regimens for such patients.

Hematopoietic stem cell mobilization strategies to support high-dose chemotherapy: A focus on relapsed/refractory germ cell tumors

High-dose chemotherapy (HDCT) with autologous hematopoietic stem cell transplantation has been explored and has played an important role in the management of patients with high-risk germ cell tumors (GCTs) who failed to be cured by conventional chemotherapy. Hematopoietic stem cells (HSCs) collected from the peripheral blood, after appropriate pharmacologic mobilization, have largely replaced bone marrow as the principal source of HSCs in transplants. As it is currently common practice to perform tandem or multiple sequential cycles of HDCT, it is anticipated that collection of large numbers of HSCs from the peripheral blood is a prerequisite for the success of the procedure. Moreover, the CD34+ cell dose/kg of body weight infused after HDCT has proven to be a major determinant of hematopoietic engraftment, with patients who receive > 2 × 10⁶ CD34+ cells/kg having consistent, rapid, and sustained hematopoietic recovery. However, many patients with relapsed/refractory GCTs have been exposed to multiple cycles of myelosuppressive chemotherapy, which compromises the efficacy of HSC mobilization with granulocyte colony-stimulating factor with or without chemotherapy. Therefore, alternative strategies that use novel agents in combination with traditional mobilizing regimens are required. Herein, after an overview of the mechanisms of HSCs mobilization, we review the existing literature regarding studies reporting various HSC mobilization approaches in patients with relapsed/refractory GCTs, and finally report newer experimental mobilization strategies employing novel agents that have been applied in other hematologic or solid malignancies.

Trial Watch: Immunostimulation with recombinant cytokines for cancer therapy

Cytokines regulate virtually aspects of innate and adaptive immunity, including the initiation, execution and extinction of tumor-targeting immune responses. Over the past three decades, the possibility of using recombinant cytokines as a means to elicit or boost clinically relevant anticancer immune responses has attracted considerable attention. However, only three cytokines have been approved so far by the US Food and Drug Administration and the European Medicines Agency for use in cancer patients, namely, recombinant interleukin (IL)-2 and two variants of recombinant interferon alpha 2 (IFN-α2a and IFN-α2b). Moreover, the use of these cytokines in the clinics is steadily decreasing, mostly as a consequence of: (1) the elevated pleiotropism of IL-2, IFN-α2a and IFN-α2b, resulting in multiple unwarranted effects; and (2) the development of highly effective immunostimulatory therapeutics, such as immune checkpoint blockers. Despite this and other obstacles, research in the field continues as alternative cytokines with restricted effects on specific cell populations are being evaluated. Here, we summarize research preclinical and clinical developments on the use of recombinant cytokines for immunostimulation in cancer patients.

Pegylated granulocyte-colony stimulating factor versus non-pegylated granulocyte-colony stimulating factor for peripheral blood stem cell mobilization: A systematic review and meta-analysis

Granulocyte-colony stimulating factor (G-CSF) mobilizes and increases the amount of hematopoietic stem cells in peripheral blood, enabling its harvest by few apheresis procedures. The pegylated G-CSF has longer half-life and is given once only, which is more comfortable for patients, whereas the non-pegylated requires multiple daily injection because of its short half-life. We summarized results of randomized trials comparing the efficacy and safety of pegylated and non-pegylated G-CSF for peripheral blood stem cell mobilization. We searched the Cochrane CENTRAL, MEDLINE, EMBASE, and two conference proceedings. Two authors made the selection, extracted data and evaluated methodological quality using GRADE independently. We used random-effects model for meta-analysis. We found 3956 records and retrieved 47 full texts. We included eight randomized trials with a total number of 554 randomized and 532 analyzed subjects. The meta-analysis included five trials because not all trials reported the same outcomes. Pooling data from two studies shows no evidence for a difference in the successful mobilization rate (CD34+ cell ≥ 2 × 10⁶ /kg collected) between pegfilgrastim 6 mg (early administration) and filgrastim 5 µg/kg/day (147 participants; risk ratio (RR) 0.87, 95% confidence interval (95%CI) 0.67-1.11; P = .26). Pooling data from three studies shows no difference in the incidence of adverse events between pegylated and non-pegylated G-CSF (170 participants; RR 0.86, 95%CI 0.34-2.17; P = .75). No difference found on the quantity of CD34+ cells collected, number of apheresis procedure in successful mobilization, level of peak PB CD34+ cells achieved, and day of neutrophil and platelet engraftment.

How to manage poor mobilizers for high dose chemotherapy and autologous stem cell transplantation?

Today, peripheral blood stem cells are the preferred source of stem cells over bone marrow. Therefore, mobilization plays a crutial role in successful autologous stem cell transplantation. Poor mobilization is generally defined as failure to achieve the target level of at least 2×10⁶ CD34⁺ cells/kg body weight. There are several strategies to overcome poor mobilization: 1) Larger volume Leukapheresis (LVL) 2) Re-mobilization 3) Plerixafor 4) CM+Plerixafor (P)+G-CSF and 5) Bone Marrow Harvest. In this review, the definitions of successful and poor mobilization are discussed. Management strategies for poor mobilization are defined. The recent research on new agents are included.

Mobilization of hematopoietic progenitor cells for autologous transportation: consensus recommendations

Selected patients with certain hematological malignancies and solid tumors have the potential to achieve long-term survival with autologous hematopoietic progenitor cell transplant. The collection of these cells in peripheral blood avoids multiple bone marrow aspirations, results in faster engraftment and allows treatment of patients with infection, fibrosis, or bone marrow hypocellularity. However, for the procedure to be successful, it is essential to mobilize a sufficient number of progenitor cells from the bone marrow into the blood circulation. Therefore, a group of Brazilian experts met in order to develop recommendations for mobilization strategies adapted to the reality of the Brazilian national health system, which could help minimize the risk of failure, reduce toxicity and improve the allocation of financial resources.

Decision-tree algorithm for optimized hematopoietic progenitor cell-based predictions in peripheral blood stem cell mobilization

BACKGROUND

Enumerating hematopoietic progenitor cells (HPCs) by using an automated hematology analyzer is a rapid, inexpensive, and simple method for predicting a successful harvest compared with enumerating circulating CD34+ cells. However, the optimal HPC cutoff count and the indicating factors to be considered for improved predicting have not yet been determined.

STUDY DESIGN AND METHODS

Between 2007 and 2012, a total of 189 consecutive patients who proceeded to peripheral blood stem cell (PBSC) harvesting were retrospectively recruited. Baseline characteristics were analyzed to identify the risk factors for a failed harvest, which were defined as less than 2 × 10(6) CD34+ cells/kg. Variables identified by multivariate logistic regression and correlation analysis for predicting a successful harvest were subjected to classification and regression tree (CART) analysis.

RESULTS

PBSCs were successfully harvested in 154 (81.5%) patients. An age of at least 60 years, a diagnosis of a solid tumor, at least five prior chemotherapy cycles, prior radiotherapy, and mobilization with granulocyte-colony-stimulating factor alone or high-dose cyclophosphamide were independent baseline predictors of poor mobilization. In CART analysis, patients with zero to two host risk factors and either higher HPC (≥28 × 10(6) /L) or mononuclear cell (MNC; ≥3.5 × 10(9) /L) counts were categorized as good mobilizers and their harvest success rate was 92.3%. By contrast, 30.3% of harvests were adequate in the patients with three to five host risk factors and lower HPC and MNC counts.

CONCLUSION

A CART algorithm incorporating host predictors and HPC and MNC counts improves predictions in a successful harvest and might reduce the necessity of monitoring peripheral CD34+ cells.

Trial Watch-Immunostimulation with cytokines in cancer therapy

During the past decade, great efforts have been dedicated to the development of clinically relevant interventions that would trigger potent (and hence potentially curative) anticancer immune responses. Indeed, developing neoplasms normally establish local and systemic immunosuppressive networks that inhibit tumor-targeting immune effector cells, be them natural or elicited by (immuno)therapy. One possible approach to boost anticancer immunity consists in the (generally systemic) administration of recombinant immunostimulatory cytokines. In a limited number of oncological indications, immunostimulatory cytokines mediate clinical activity as standalone immunotherapeutic interventions. Most often, however, immunostimulatory cytokines are employed as immunological adjuvants, i.e., to unleash the immunogenic potential of other immunotherapeutic agents, like tumor-targeting vaccines and checkpoint blockers. Here, we discuss recent preclinical and clinical advances in the use of some cytokines as immunostimulatory agents in oncological indications.

Optimizing mobilization strategies in difficult-to-mobilize patients: The role of plerixafor

Peripheral blood stem cell collection is currently the most widely used source for hematopoietic autologous transplantation. Several factors such as advanced age, previous chemotherapy, disease and marrow infiltration at the time of mobilization influence the efficacy of CD34(+) progenitor cell mobilization. Despite the safety and efficiency of the standard mobilization protocols (G-CSF ± chemotherapy), there is still a significant amount of mobilization failure rate (10-40%), which necessitate novel agents for effective mobilization. Plerixafor, is a novel agent, has been recently approved for mobilization of hematopoietic stem cells (HSCs). The combination of Plerixafor with G-CSF provides the collection of large numbers of stem cells in fewer apheresis sessions and can salvage those who fail with standard mobilization regimens. The development and optimization of practical algorithms for the use Plerixafor is crucial to make hematopoietic stem cell mobilization more efficient in a cost-effective way. This review is aimed at summarizing how to identify poor mobilizers, and define rational use of Plerixafor for planning mobilization in hard-to-mobilize patients.

The current status in hematopoietic stem cell mobilization

Hemotopoietic stem cell mobilization with cytokines alone, has still been widely accepted as the initial attempt for stem cell mobilization. Chemotherapy based mobilization can be preferred as first choice in high risk patients or for remobilization. But mobilization failure still remains to be a problem in one third of patients. Salvage mobilization strategies have been composed to give one more chance to 'poor mobilizers'. Synergistic effect of a reversible inhibitor of CXCR4, plerixafor, with G-CSF has opened a new era for these patients. Preemptive approach in predicted poor mobilizers, immediate salvage approach for patients with suboptimal mobilization or remobilization approach of plerixafor in failed mobilizers have all been demonstrated convincing results in various studies. Alternative CXCR4 inhibitors, VLA4 inhibitors, bortezomib, parathormone have also been emerged as novel agents for mobilization failure.

Classification of current anticancer immunotherapies

During the past decades, anticancer immunotherapy has evolved from a promising therapeutic option to a robust clinical reality. Many immunotherapeutic regimens are now approved by the US Food and Drug Administration and the European Medicines Agency for use in cancer patients, and many others are being investigated as standalone therapeutic interventions or combined with conventional treatments in clinical studies. Immunotherapies may be subdivided into "passive" and "active" based on their ability to engage the host immune system against cancer. Since the anticancer activity of most passive immunotherapeutics (including tumor-targeting monoclonal antibodies) also relies on the host immune system, this classification does not properly reflect the complexity of the drug-host-tumor interaction. Alternatively, anticancer immunotherapeutics can be classified according to their antigen specificity. While some immunotherapies specifically target one (or a few) defined tumor-associated antigen(s), others operate in a relatively non-specific manner and boost natural or therapy-elicited anticancer immune responses of unknown and often broad specificity. Here, we propose a critical, integrated classification of anticancer immunotherapies and discuss the clinical relevance of these approaches.

Trial watch: Immunostimulatory cytokines in cancer therapy

Tumor-targeting immune responses provide a significant contribution to (when they do not entirely account for) the clinical activity of diverse antineoplastic regimens, encompassing not only a large panel of immunotherapeutic strategies but also conventional cytotoxic molecules, targeted anticancer agents and irradiation. In line with this notion, several approaches have been devised to elicit novel or boost existing anticancer immune responses, including the administration of immunomodulatory cytokines. Such a relatively unspecific intervention suffices to mediate clinical effects in (at least a subset of) patients bearing particularly immunogenic tumors, like melanoma and renal cell carcinoma. More often, however, immunostimulatory cytokines are administered to boost the immunogenic potential of other agents, including (but not limited to) immune checkpoint-blocking antibodies, anticancer vaccines, oncolytic viruses and immunogenic chemotherapeutics. Here, we summarize the latest advances in the clinical development of recombinant cytokines as an immunomodulatory intervention for cancer therapy.

Granulocyte colony-stimulating factor receptor mutations in myeloid malignancy

Granulocyte colony-stimulating factor is a cytokine able to stimulate both myelopoiesis and hematopoietic stem cell mobilization, which has seen it used extensively in the clinic to aid hematopoietic recovery. It acts specifically via the homodimeric granulocyte colony-stimulating factor receptor (G-CSFR), which is principally expressed on the surface of myeloid and hematopoietic progenitor cells. A number of pathogenic mutations have now been identified in CSF3R, the gene encoding G-CSFR. These fall into distinct classes, each of which is associated with a particular spectrum of myeloid disorders, including malignancy. This review details the various CSF3R mutations, their mechanisms of action, and contribution to disease, as well as discussing the clinical implications of such mutations.

The effect of gradual increment in rhG-CSF dose on stem cell yields in patients with multiple myeloma mobilized with intermediate dose cyclophosphamide plus rhG-CSF

Cyclophosphamide along with recombinant human granulocyte-colony stimulating factor (rhG-CSF) is a commonly used strategy for mobilization. However, the optimal timing for rhG-CSF initiation after cyclophosphamide has not been determined as conclusively as has the G-CSF dose. In this paper, we aimed to present gradual dose increment of rhG-CSF between the third day of mobilization and time to apheresis that is started with 5 μg/kg (from day 3 to day 7) and continued with 10 μg/kg (from day 8 to time to apheresis) for peripheral blood stem cell (PBSC) mobilization in multiple myeloma (MM) patients and its effect on stem cell yield and mobilization success. Data from 30 consecutive patients with MM who underwent PBSC mobilization between October 2011 and June 2013, were retrospectively reviewed. While twenty-eight of 30 patients (93.3%) were successfully mobilized, 2 patients (6.7%) had mobilization failure. The final median CD34+ cell dose harvested from the patients was 9.5×10(6)/kg. The median number of apheresis was 2.5 (range, 0-3). Twenty-four patients (80%) yielded >2×10(6) CD34+ cells/kg in one apheresis procedure. In conclusion, our regimen might be used to decrease the mobilization failure regarding the low dose rhG-CSF use and provide a cost effective strategy.

Optimizing autologous stem cell mobilization strategies to improve patient outcomes: consensus guidelines and recommendations

Autologous hematopoietic stem cell transplantation (aHSCT) is a well-established treatment for malignancies such as multiple myeloma (MM) and lymphomas. Various changes in the field over the past decade, including the frequent use of tandem aHSCT in MM, the advent of novel therapies for the treatment of MM and lymphoma, and the addition of new stem cell mobilization techniques, have led to the need to reassess current stem cell mobilization strategies. Mobilization failures with traditional strategies are common and result in delays in treatment and increased cost and resource utilization. Recently, plerixafor-containing strategies have been shown to significantly reduce mobilization failure rates, but the ideal method to maximize stem cell yields and minimize costs associated with collection has not yet been determined. A panel of experts convened to discuss the currently available data on autologous hematopoietic stem cell mobilization and transplantation and to devise guidelines to optimize mobilization strategies. Herein is a summary of their discussion and consensus.

GCSF with or without chemotherapy compared to Plerixafor with GCSF as salvage mobilization regimen in patients with multiple myeloma and lymphoma: collection effectiveness and cost effectiveness analysis

INTRODUCTION

Plerixafor is a novel mobilizing agent of peripheral blood stem cells (PBSCs) in lymphoma and multiple myeloma (MM) patients whose cells mobilize poorly. Due to the substantial cost associated with its use, we aimed to compare the effectiveness and cost effectiveness of Plerixafor + GCSF (PG) versus GCSF ± Chemotherapy (GC) as salvage mobilization regimens.

METHODS

The charts of consecutive lymphoma and MM patients who had undergone at least one previous attempt of PBSCs mobilization that failed or resulted in an insufficient cell dose for transplant between 2007 and 2010 were retrospectively reviewed. Patients identified received salvage mobilization with GC (prior to 2009) or PG after Plerixafor's FDA approval. Data collected included demographics, medical histories, apheresis yields and transplant outcome. The cost effectiveness analysis was from the perspective of the Jordanian Ministry of Health. The incremental cost effectiveness ratio (ICER) was calculated by dividing the difference in cost by the difference in effectiveness for the two regimens.

RESULTS

Five patients received GC and twelve received PG. A minimum CD34+ cell dose of 2 × 10(6) cells/kg was collected from 8 patients (67%) in the PG group compared to 3 (60%) in the GC group (p=0.79). The average costs were US$8570 and US$25,700 for the GC group and the PG group, respectively. The ICER was US$244,714 per successful stem cell collection.

CONCLUSION

Salvage Plerixafor use showed a non-significant improvement in PBSCs collection with a significant increase in cost. Prospective comparative effectiveness studies are warranted to inform the optimal salvage mobilization regimen. To our knowledge, this is the first study from the Middle East to describe the effectiveness and cost effectiveness of Plerixafor.

Trial Watch: Immunostimulatory cytokines

During the past two decades, the notion that cancer would merely constitute a cell-intrinsic disease has gradually been complemented by a model postulating that the immune system plays a relevant role during all stages of oncogenesis and tumor progression. Along with this conceptual shift, several strategies have been devised to stimulate tumor-specific immune responses, including relatively unselective approaches such as the systemic administration of adjuvants or immunomodulatory cytokines. One year ago, in the July issue of OncoImmunology, we described the main biological features of this large group of proteins and discussed the progress of ongoing clinical studies evaluating their safety and therapeutic potential in cancer patients. Here, we summarize the latest developments in this area of clinical research, focusing on high impact studies that have been published during the last 13 mo and clinical trials launched in the same period to investigate which cytokines can be employed as safe and efficient immunostimulatory interventions against cancer.

Advances in stem cell mobilization

The use of mobilized peripheral blood stem cells (PBSCs) has largely replaced the use of bone marrow as a source of stem cells for both allogeneic and autologous stem cell transplantation. G-CSF with or without chemotherapy is the most commonly used regimen for stem cell mobilization. Some donors or patients, especially the heavily pretreated patients, fail to mobilize the targeted number of stem cells with this regimen. A better understanding of the mechanisms involved in hematopoietic stem cell (HSC) trafficking could lead to the development of newer mobilizing agents and therapeutic approaches. This review will cover the current methods for stem cell mobilization and recent developments in the understanding of the biology of stem cells and the bone marrow microenvironment.

Predictive factors for inadequate stem cell mobilization in Chinese patients with NHL and HL: 14-year experience of a single-center study

BACKGROUND

Factors affecting progenitor cell mobilization in patients with non-Hodgkin's lymphoma (NHL) and Hodgkin's lymphoma (HL) are incompletely understood. The aim of this retrospective study was to determine which factors are crucial for effective mobilization and collection of autologous peripheral blood stem cells (PBSC) prior to transplantation in Chinese patients.

PATIENTS AND METHODS

A total of 239 patients with lymphoma (198 NHL and 41 HL patients) underwent PBSC collection after mobilization with granulocyte-colony-stimulating factor (G-CSF) or G-CSF plus chemotherapy priming.

RESULTS

Patient characteristics at diagnosis and transplant, including low Eastern Cooperative Oncology Group score (P = 0.013), lack of extranodal invasion (P = 0.034), previously administered radiotherapy regimens (P = 0.040), treatment with platinum prior to mobilization (P = 0.042), previous chemotherapy regimens (P = 0.001) and cycles (P < 0.001), and chemotherapy regimens (P < 0.001) were statistically significant for successful mobilization in multivariate analysis. Premobilization factors, including previous radiotherapy (P = 0.009), previous chemotherapy regimens (P = 0.043) and cycles (P = 0.039), low platelet count prior to mobilization (P = 0.042), and lower CD34+ cells in peripheral blood (PB) (P = 0.050) or bone marrow (BM) (P = 0.007) were considered possibly predictive of poor mobilization. We found the patients who had chemosensitive lymphoma had worse progress-free survival (PFS) than the patients with initial treatment and high risks (P = 0.017).

CONCLUSION

Our analysis showed that high amounts of chemotherapy, radiotherapy, low platelet count, chemosensitive recurrent patients, combination chemotherapy plus G-CSF and low CD34+ cells in BM prior to mobilization could emerged as important predictive factors for mobilization failure in Chinese patients with NHL and HL.

Harvesting, processing and inventory management of peripheral blood stem cells

By 2003, 97% autologous transplants and 65% of allogeneic transplants in Europe used mobilised peripheral blood stem cells (PBSC). Soon after their introduction in the early 1990's, PBSC were associated with faster haemopoietic recovery, fewer transfusions and antibiotic usage, and a shorter hospital stay. Furthermore, ease and convenience of PBSC collection made them more appealing than BM harvests. Improved survival has hitherto been demonstrated in patients with high risk AML and CML. However, the advantages of PBSC come at a price of a higher incidence of extensive chronic GVHD. In order to be present in the blood, stem cells undergo the process of “mobilisation” from their bone marrow habitat. Mobilisation, and its reciprocal process – homing – are regulated by a complex network of molecules on the surface of stem cells and stromal cells, and enzymes and cytokines released from granulocytes and osteoclasts. Knowledge of these mechanisms is beginning to be exploited for clinical purposes. In current practice, stem cell are mobilised by use of chemotherapy in conjunction with haemopoietic growth factors (HGF), or with HGF alone. Granulocyte colony stimulating factor has emerged as the single most important mobilising agent, due to its efficacy and a relative paucity of serious side effects. Over a decade of use in healthy donors has resulted in vast experience of optimal dosing and administration, and safety matters. PBSC harvesting can be performed on a variety of cell separators. Apheresis procedures are nowadays routine, but it is important to be well versed in the possible complications in order to avoid harm to the patient or donor. To ensure efficient collection, harvesting must begin when sufficient stem cells have been mobilised. A rapid, reliable, standardized blood test is essential to decide when to begin harvesting; currently, blood CD34+ cell counting by flow cytometry fulfils these criteria. Blood CD34+ cell counts strongly correlate with the apheresis yields. These are, in turn, predictive of the speed of haemopoietic recovery after transplantation, which has helped establish the adequate cell dose for transplantation. Following collection, PBSC may be transfused unmanipulated, processed to select specific cell subtypes, or stored for future use. Cryopreservation techniques allow long term storage of stem cells without significant loss of viability. Increasingly demanding calls for safety led to introduction of vapour phase storage, separate storage of infected material, and mandatory quality control measures at all stages of the cryopreservation process and subsequent thawing and transfusion. At the same time, safety of the personnel working in stem cell processing and storage laboratories is safeguarded by a set of regulations devised to minimize the risk of infection, injury or hypoxia. Requirements for quality and safety have been shaped into a number of documents and directives in Europe and USA, emphasising the importance of product traceability, reporting of adverse reactions, quality management systems (standard operating procedures, guidelines, training records, reporting mechanisms and records), requirements for cell reception, quarantine, process control, validation and storage. Establishments that collect, process and store stem cells must be accredited or licensed by appropriate national or international authorities on a regular basis. These regulatory measures have recently become law across the European Union.

Proposed definition of 'poor mobilizer' in lymphoma and multiple myeloma: an analytic hierarchy process by ad hoc working group Gruppo ItalianoTrapianto di Midollo Osseo

Many lymphoma and myeloma patients fail to undergo ASCT owing to poor mobilization. Identification of poor mobilizers (PMs) would provide a tool for early intervention with new mobilization agents. The Gruppo italianoTrapianto di Midollo Osseo working group proposed a definition of PMs applicable to clinical trials and clinical practice. The analytic hierarchy process, a method for group decision making, was used in setting prioritized criteria. Lymphoma or myeloma patients were defined as ‘proven PM' when: (1) after adequate mobilization (G-CSF 10 μg/kg if used alone or ⩾5 μg/kg after chemotherapy) circulating CD34⁺ cell peak is <20/μL up to 6 days after mobilization with G-CSF or up to 20 days after chemotherapy and G-CSF or (2) they yielded <2.0 × 10⁶ CD34⁺ cells per kg in ⩽3 apheresis. Patients were defined as predicted PMs if: (1) they failed a previous collection attempt (not otherwise specified); (2) they previously received extensive radiotherapy or full courses of therapy affecting SC mobilization; and (3) they met two of the following criteria: advanced disease (⩾2 lines of chemotherapy), refractory disease, extensive BM involvement or cellularity <30% at the time of mobilization; age ⩾65 years. This definition of proven and predicted PMs should be validated in clinical trials and common clinical practice.

Peripheral Blood Stem Cell Mobilization Tactics

OBJECTIVE

To evaluate the methods and collection techniques currently used in stem cell mobilization for patients undergoing autologous transplantation.

DATA SOURCES

Literature search was performed through PubMed (1948-August 2009) and MEDLINE (1977-August 2009). Reference citations from publications identified were also reviewed.

STUDY SELECTION AND DATA EXTRACTION

All literature identified was reviewed for inclusion. Original research and retrospective cohorts, along with previously published systematic reviews of stem cell mobilization and growth factors, were evaluated. Abstract data on plerixafor were also reviewed.

DATA SYNTHESIS

Successful mobilization of an adequate number of progenitor cells can help ensure and improve time to neutrophil and platelet engraftment. A variety of methods have been studied to find the safest and most predictable mobilization of CD34+ progenitor cells, including use of single agents or the combinations of hematopoietic growth factors, chemotherapy, and a novel chemokine receptor 4 antagonist. Currently, granulocyte colony-stimulating factor (G-CSF) 10 Mg/kg daily started 4 days prior to apheresis remains the standard of care for initial mobilization therapy. In patients who fail to mobilize or who are at high risk for mobilization failure, cyclophosphamide in conjunction with G-CSF may be used. Plerixafor, a novel chemokine receptor antagonist, in combination with G-CSF has demonstrated superiority for achieving collection goals compared to G-CSF alone in 2 Phase 3 trials.

CONCLUSIONS

The optimal mobilization strategy is still unknown; however, colony-stimulating factors remain the most commonly used mobilization agents. Currently, chemotherapy or plerixafor in combination with G-CSF is a reasonable option in heavily pretreated and hard-to-mobilize patients with non-Hodgkin's lymphoma and multiple myeloma.

International myeloma working group (IMWG) consensus statement and guidelines regarding the current status of stem cell collection and high-dose therapy for multiple myeloma and the role of plerixafor (AMD 3100)

Multiple myeloma is the most common indication for high-dose chemotherapy with autologous stem cell support (ASCT) in North America today. Stem cell procurement for ASCT has most commonly been performed with stem cell mobilization using colony-stimulating factors with or without prior chemotherapy. The target CD34+ cell dose to be collected as well as the number of apheresis performed varies throughout the country, but a minimum of 2 million CD34+ cells/kg has been traditionally used for the support of one cycle of high-dose therapy. With the advent of plerixafor (AMD3100) (a novel stem cell mobilization agent), it is pertinent to review the current status of stem cell mobilization for myeloma as well as the role of autologous stem cell transplantation in this disease. On June 1, 2008, a panel of experts was convened by the International Myeloma Foundation to address issues regarding stem cell mobilization and autologous transplantation in myeloma in the context of new therapies. The panel was asked to discuss a variety of issues regarding stem cell collection and transplantation in myeloma especially with the arrival of plerixafor. Herein, is a summary of their deliberations and conclusions.

Mobilization strategies for the collection of peripheral blood progenitor cells: Results from a pilot study of delayed addition G-CSF following chemotherapy and review of the literature

OBJECTIVE

Given the potential to limit cost, we conducted a pilot study evaluating delayed, low-dose granulocyte colony-stimulating factor (G-CSF) following chemotherapy for the procurement of peripheral blood progenitor cells (PBPCs) for autologous transplantation and reviewed the relevant literature.

PATIENTS AND METHODS

Twenty-eight patients with various malignancies received cyclophosphamide 4 gm/m(2) and paclitaxel 170 mg/m2 followed by G-CSF 300 microg/d or 480 microg/d starting day +5 until two to four daily large volume leukapheresis yielded > or =5.0 x 10(6) CD34+ cells. We searched MEDLINE, Pubmed, and EMBASE databases from 1990 to the present to identify papers on PBPC procurement using delayed G-CSF (starting day +4 or later) following chemotherapy.

RESULTS

G-CSF was administered for a median of 9 days at an average cost of 1260 USD per 70-kg patient. Collection was initiated at a median of 12 days after chemotherapy. A median 2.5 (range 2-4) apheresis were performed yielding an average daily CD34+ collection of 6.9 x 10(6)/kg (range 0.35-56.7). After one apheresis, 82% and 57% of patients collected > or =2.5 x 10(6)/kg and > or =5.0 x 10(6)/kg, respectively. Ultimately, 89% collected > or =5.0 x 10(6)/kg. Febrile neutropenia and catheter-related infection developed in five and two patients, respectively. All patients proceeded to transplantation and engrafted successfully with a median of 14.9 x 10(6)/kg (range 1.05-113) cells infused. Eleven published reports were identified involving 590 patients of whom 498 received G-CSF at a dose range of 250 microg/d to 10 microg/kg/d starting day +4 to 15 for a period of 4 to 9 days for PBPC procurement. Among these reports, 62 to 100% and 33 to 96% of patients collected > or =2 to 2.5 x 10(6) and > or =5.0 x 10(6) CD34+ cells, respectively.

CONCLUSION

The use of delayed, low-dose G-CSF plus chemotherapy for stem cell mobilization was feasible and provides further evidence supporting this potentially cost-effective strategy. A review of the literature supports our findings and emphasizes the need for larger studies to address this issue.

Prediction of target CD34 positive cells following leukopheresis in children with neuroblastoma

BACKGROUND

Myeloablative chemotherapy followed by autologous stem cell transplantation (ASCT) may improve long-term survival in children with disseminated neuroblastoma. In children it is important to be able to ascertain when to start the leukopheresis in order to keep the number of procedures to a minimum.

PROCEDURE

Twenty-three children with high-risk neuroblastoma with a median weight of 13 kg (range 8-16 kg). Stem cell collection was planned to start at day 14 after the start of the preceding induction standard chemotherapy and after 4 days of G-CSF treatment at 10 microg/kg body weight once daily subcutaneously. Normal volume leukopheresis (median 2.2 times the blood volume of the child) was carried out using a CS-3000 Plus Blood Cell Separator. A pre-collection peripheral blood CD34+ count of >20/microl was a prerequisite for initiating the stem cell collection.

RESULTS

Timely leukopheresis was carried out in 19/23 patients. In 17 (74%) of the patients the target number of CD34+ cells/kg body weight was obtained in one procedure; in the remaining the target number of stem cells was obtained after leukopheresis on the following day. A highly significant correlation was found between the pre-harvest CD34+ count from the peripheral blood and the total number of collected CD34+ cells/kg (r = 0.79, P < 0.001).

CONCLUSION

When the pre-harvest CD34+ count was >40/microl, a sufficient number of CD34+ stem cells was collected in a single procedure in 15 out of 16 cases.

ESHAP+fixed dose G-CSF as autologous peripheral blood stem cell mobilization regimen in patients with relapsed or refractory diffuse large cell and Hodgkin's lymphoma: a single institution result of 127 patients

From 1996 to November 2004, 131 consecutive patients with relapsed or refractory diffuse large cell lymphoma (DLCL) and Hodgkin's lymphoma (HD) received ESHAP as mobilization chemotherapy before autologous peripheral blood stem cell transplant (ASCT). Patients received fixed dose G-CSF 300 microg SC bid starting 24-36 h after finishing mobilizing ESHAP. In all, four patients failed mobilization and are excluded. Characteristics of 127 patients: 68 males: 59 females. DLCL 49: HD 78. Initial stage I:II:III:IV:unknown was 15:34:33:42:3. Median age at ASCT 26 years. Median prior chemotherapy cycles were six [<6 (17 patients), 6-8 (90 patients), >8 (20 patients)]. Median ESHAP cycle used as mobilizer was third. Patients required 1, 2, 3, 4 apheresis were 93:25:8:1. Median total CD34+ cells/kg collected were 6.9 x 10(6) (DLCL 5.17 x 10(6) and HD 7.6 x 10(6)), patients weighing < or = 70 kg (93 patients) 6.54 x 10(6) and >70 kg (34 patients) 7.44 x 10(6) (P = 0.59), one apheresis (93 patients) 8.6 x 10(6)/kg and >1 apheresis (34 patients) 4.5 x 10(6) (P = 0.001). We conclude that ESHAP and G-CSF 300 microg SC bid is an effective mobilizing regimen even in patients >70 kg and most patients require only 1-2 apheresis.

Current status of stem cell transplantation for multiple myeloma

Stem cell transplantation for myeloma has become a standard of care for newly diagnosed patients. Current evidence favors tandem transplants for those patients not achieving a complete or very good partial response (<90%) after the first transplant. Transplantation is safe and has been shown to prolong survival even in patients 65 to 70 years of age. Whether the new agents thalidomide, lenalidomide, and bortezomib will have an impact on the survival advantage of stem cell transplantation is unknown.

PBSC mobilization

Intentional recruitment of hematopoietic stem cells from bone marrow to peripheral blood is a clinical process termed peripheral blood stem cell (PSBC) mobilization. Mobilized PSBC has replaced bone marrow as the preferred source of stem cells for patients undergoing high-dose chemotherapy because of rapid and durable engraftment and reconstitution of functional bone marrow. Although the mechanism involved in the process of PBSC mobilization by cytokines is largely unknown, granulocyte colony-stimulating factor (G-CSF) alone or chemotherapy combined with GCSF is used as a mobilizing agent in current clinical practice. To date, G-CSF is the best cytokine for PBSC mobilization. However, there are some controversies in its efficacy (poor mobilizer) and safety (in allogeneic donors). Recent research progress has revealed some part of the mechanistic scenarios of PBSC mobilization and found promising candidates for the agents for PBSC mobilization. Until the research at molecular and cellular levels elucidates the precise mechanisms, collecting and comparing clinical observations is the best way to find more optimal condition for PBSC mobilization.

High-dose thiotepa, melphalan and carboplatin (TMCb) followed by autologous peripheral blood stem cell transplantation in patients with lymphoma – a retrospective evaluation

The purpose of this evaluation was to investigate the efficacy of high-dose chemotherapy with thiotepa, melphalan, and carboplatin (TMCb), and of autologous peripheral blood stem cell (PBSC) infusion in patients with aggressive non-Hodgkin's lymphoma (NHL) or Hodgkin's disease (HD). A total of 42 patients, 23 with intermediate-grade NHL and 19 with HD, received thiotepa (500 mg/m2), melphalan (100 mg/m2), and carboplatin (1050-1350 mg/m2) followed by autologous PBSC infusion. Of 21 patients with more advanced disease, four had primary refractory disease, one was in complete remission (CR)-2, 11 were in first refractory relapse, and five were beyond first relapse. Of 21 patients with less advanced disease, two were in CR-1, four were in CR-2, and 15 were in first responding relapse. In all, 14 patients (33%) had received prior radiotherapy prohibiting a total-body irradiation (TBI)-based conditioning regimen. The projected 2-year probabilities of survival, event-free survival (EFS), and relapse for all patients were 0.65, 0.60, and 0.21 (0.85, 0.80, and 0.10 for patients with less advanced disease and 0.47, 0.42, and 0.33 for patients with more advanced disease). The probability of nonrelapse mortality in the first 100 days was 0.12. Grade 3-4 regimen-related toxicities (RRT) occurred in five of 42 (12%) patients and death due to grade-4 RRT occurred in only one (2.5%) patient. These preliminary data suggest that 0.42% EFS in this study for advanced disease patients is highly encouraging and high-dose TMCb followed by autologous PBSC transplantation is well tolerated as well as an effective regimen in patients with intermediate-grade NHL or HD, and may be comparable to some previously used regimens including TBI-based regimens.

A randomised study comparing peripheral blood progenitor mobilisation using intermediate-dose cyclophosphamide plus lenograstim with lenograstim alone

We conducted a prospective randomised study to compare the efficiency of out-patient progenitor cell mobilisation using either intermediate-dose cyclophosphamide (2 g/m(2)) and lenograstim at 5 micrograms/kg (Cyclo-G-CSF group, n=39) or lenograstim alone at 10 micrograms/kg (G-CSF group, n=40). The end points were to compare the impact of the two regimens on mobilisation efficiency, morbidity, time spent in hospital, the number of apheresis procedures required and engraftment kinetics. Successful mobilisation was achieved in 28/40 (70%) in the G-CSF group vs 22/39 (56.4%) for Cyclo-G-CSF (P=0.21). The median number of CD34+ cells mobilised was 2.3 x 10(6)/kg and 2.2 x 10(6)/kg for G-CSF and cyclo-G-CSF arms following a median of two apheresis procedures. Nausea and vomiting and total time spent in the hospital during mobilisation were significantly greater after Cyclo-G-CSF (P<0.05). Rapid neutrophil and platelet engraftment was achieved in all transplanted patients in both groups. In conclusion, G-CSF at 10 micrograms/kg was as efficient at mobilising progenitor cells as a combination of cyclophosphamide and G-CSF with reduced hospitalisation and side effects and prompt engraftment. When aggressive in-patient cytoreductive regimens are not required to both control disease and generate progenitor cells, the use of G-CSF alone appears preferable to combination with intermediate-dose cyclophosphamide.

Effect of prior chemotherapy on hematopoietic stem cell mobilization

A number of studies have suggested that prior chemotherapy correlates negatively with the efficiency of hematopoietic stem cell mobilization. However, little data exist with regard to the relative effects of the specific chemotherapeutic drug classes. We retrospectively reviewed the records of 201 consecutive patients with nonmyeloid malignancies undergoing CD34+ cell mobilization with chemotherapy+granulocyte colony-stimulating factor (G-CSF). The number of prior chemotherapy courses correlated negatively with the peripheral CD34+ cell concentration (pCD34) on the first day of collection (P<0.001). No significant correlation was found for age, gender, tumor primary, mobilization chemotherapy regimen, disease status, marrow involvement, prior radiation therapy, or dose and timing of G-CSF administration. When the number of courses of individual classes of chemotherapeutic agents was correlated with pCD34, only exposures to platinum compounds (P=0.001) and alkylating agents (P=0.01) were found to be independent negative predictive factors for pCD34. Within classes, DNA crosslinking agents and etoposide appeared possibly more damaging than DNA methylating agents and doxorubicin, respectively. None of the drug classes showed evidence of recovery. We conclude that exposure to chemotherapy, especially platinum compounds and alkylating agents, should be minimized prior to mobilization.

Stem cell mobilization in multiple myeloma patients: Do we need an age-adjusted regimen for the elderly?

The upper age limit for autologous progenitor cell transplantation in multiple myeloma patients is increasing continuously. We examined whether this shift in the age of pretreated myeloma patients requires modification of mobilization regimen. We compared retrospectively 21 consecutive progenitor cell mobilizations in 15 pts < 60 years (median age 56, range 37-59) with 33 consecutive mobilizations in 23 pts > 60 years (median age 65, range 60-73) of age. The number of CD34 positive circulating cells before scheduled leukapheresis was a mean of 67,935 cells/mL (SEM +/- 17,614) in the younger population and a mean of 19,069 (SEM +/- 5,396) for older pts (P = 0.0027). In patients >60 years, 13/33 mobilizations (including 2 patients with 2 failing attempts) were not successful (39%), compared to 6/21 mobilizations (29%, including 1 patient with 3 failing attempts) in the younger population. The increased number of progenitor cells in the grafts of younger patients led to a more rapid regeneration of leukocytes and platelets after stem cell infusion. Our data show that stem cell mobilization in older multiple myeloma patients is inferior compared to a younger patient population. There is a trend towards more leukapheresis until the target stem cell dose has been collected, and the decreased number of progenitor cells in the actual graft delays engraftment of leukocytes and platelets. The overall number of unsuccessful mobilization attempts, however, did not differ significantly between both age groups. A special "age-adjusted" increase in the dose of growth factors seems unjustified. Improvements in timing of leukapheresis, growth factor application, and mobilizing chemotherapy regimen as well as the use of alternative cytokines should be investigated for both age groups.