The role of stem cell mobilization regimen on lymphocyte collection yield in patients with multiple myeloma

Mobilization Strategies in Myeloma Patients Intended for Autologous Hematopoietic Cell Transplantation

Background

Multiple myeloma is currently the leading indication for autologous hematopoietic cell transplantation (AHCT). A prerequisite for AHCT is mobilization and collection of adequate blood graft to support high-dose therapy. Current mobilization strategies include granulocyte colony-stimulating factor (G-CSF) alone or in combination with chemotherapy most commonly cyclophosphamide (CY). More recently, plerixafor has become into agenda especially in patients who mobilize poorly. In the selection of a mobilization method, several factors should be considered.

Summary

Preplanned collection target is important as G-CSF plus plerixafor is more effective in the mobilization of CD34+ cells than G-CSF alone. On the other hand, CY plus G-CSF is superior to G-CSF only mobilization. Previous therapy and age of the patients are important considerations as G-CSF alone may not be effective enough in patients with risk factors for poor mobilization. These factors include extensive lenalidomide exposure, irradiation to bone marrow-bearing sites, higher age, or a previous mobilization failure. Also, local preferences and experiences as well as the number of apheresis needed are important issues as well as cost-effectiveness considerations. Mobilization method used may have implication for cellular composition of collected grafts, which might have an impact on posttransplant events such as hematologic and immune recovery in addition to also potential long-term outcomes.

Key Message

Currently, G-CSF alone and preemptive plerixafor if needed might be considered as a standard mobilization strategy in MM patients intended for AHCT.

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.

The Impact of Infused Autograft Absolute Numbers of Immune Effector Cells on Survival Post-Autologous Stem Cell Transplantation

Autologous stem cell transplantation treatment has been viewed as a therapeutic modality to enable the infusion of higher doses of chemotherapy to eradicate tumor cells. Nevertheless, recent reports have shown that, in addition to stem cells, infusion of autograft immune effector cells produces an autologous graft-versus-tumor effect, similar to the graft-versus-tumor effect observed in allogeneic-stem cell transplantation, but without the clinical complications of graft-versus-host disease. In this review, I assess the impact on clinical outcomes following infusions of autograft-antigen presenting cells, autograft innate and adaptive immune effector cells, and autograft immunosuppressive cells during autologous stem cell transplantation. This article is intended to provide a platform to change the current paradigmatic view of autologous stem cell transplantation, from a high-dose chemotherapy-based treatment to an adoptive immunotherapeutic intervention.

Infused Autograft Absolute Lymphocyte Count Predicts Superior Survival in Diffuse Large B Cell Lymphoma Patients Post-Autologous Peripheral Blood Hematopoietic Stem Cell Transplantation: A Matched Case-Control Study

Our group published a double phase III trial showing that patients infused with an autograft absolute lymphocyte count (A-ALC) ≥0.5 × 10⁹ cells/kg experienced superior survival post-autologous peripheral blood hematopoietic stem cell transplantation (APBHSCT). Based on the results from our phase III study, as well as published retrospective studies, on April 1, 2017, our Bone Marrow Transplant Program changed our standard practice to collect an A-ALC ≥0.5 × 10⁹ cells/kg in addition to stem cells for lymphoma patients undergoing APBHSCT. The primary objective of the present study was to continue to assess the prognostic ability of A-ALC by evaluating overall survival (OS) and progression-free survival (PFS) of diffuse large B cell lymphoma (DLBCL) patients who underwent APBHSCT after April 1, 2017, compared with matched control groups at a 1:1:1 ratio with DLBCL patients infused with an A-ALC <0.5 × 10⁹ cells/kg and A-ALC ≥0.5 × 10⁹ cells/kg before April 1, 2017. Using the GREEDY algorithm, 85 DLBCL patients (cases) infused with an A-ALC ≥0.5 × 10⁹ cells/kg after April 1, 2017, were matched at a 1:1:1 ratio with control groups of DLBCL patients who underwent transplantation before April 1, 2017: patients infused with an A-ALC <0.5 × 10⁹ cells/kg (control 1) and patients infused with an A-ALC ≥0.5 × 10⁹ cells/kg (control 2) before April 1, 2017. Groups were matched in terms of sex, age, stage, lactate dehydrogenase (LDH) level, performance status, extranodal disease, International Prognostic Index (IPI), and disease status before APBHSCT (complete or partial response). Survival follow-up was truncated at 3 years from the date of transplantation. Cases, control 1, and control 2 were balanced as to age (P = .8), sex (P = .9), LDH (P = .6), performance status (P = .5), extranodal disease (P = .2), IPI (P = .6), and disease status before APBHSCT (P = .2). Cases and control 2 showed superior OS and PFS compared with control 1. Multivariate analysis including all patients continued to show A-ALC ≥0.5 × 10⁹ cells/kg as an independent predictor for OS (hazard ratio [HR], 0.382; 95% confidence interval [CI], 0.241 to 0.605; P < .0001) and PFS (HR, 0.437; 95% CI, 0.279 to 0.629; P < .0001). Our matched case-control study supports the results of previously published retrospective studies and our phase III study showing that the infusion of A-ALC is a prognostic factor for survival in DLBCL patients undergoing APBHSCT. Our findings support the practice of collecting not only enough stem cells for hematologic engraftment, but also enough immune effector cells (ie, A-ALC) to improve clinical outcomes in DLBCL patients post-APBHSCT.

Autograft immune effector cells and survival in autologous peripheral blood hematopoietic stem cell transplantation

In addition to stem cells, T-cells, natural killer cells, dendritic cells, and monocytes are also collected and infused from the autograft in patients undergoing autologous peripheral blood hematopoietic stem cell transplantation. Recent reports have shown that these autograft immune effector cells can affect the clinical outcome postautologous peripheral blood hematopoietic stem cell transplantation. In this article, I will review the clinical impact on the survival of these autograft immune effector cells conferring the concept of autologous graft versus tumor effect.

Autologous Graft-versus-Tumor Effect: Reality or Fiction?

In contrast to allogeneic hematopoietic stem cell transplantation, the current dogma is not an evidence of graft-versus-tumor effect in autologous hematopoietic stem cell transplantation; thus, it is assumed that autologous hematopoietic stem cell transplantation only relies on the high-dose chemotherapy to improve clinical outcomes. However, recent studies argue in favor of the existence of an autologous graft-versus-tumor without the detrimental complications of graft-versus-host disease due to the nonspecific immune response from the infused donor alloreactive immune effector cells in allogeneic hematopoietic stem cell transplantation. Herein, this paper reviews the clinical evidence of an autologous graft-versus-tumor effect based on the autograft collected and infused host immune effector cells and host immunity recovery after autologous hematopoietic stem cell transplantation affecting clinical outcomes in cancer patients.

Mobilized peripheral blood grafts include more than hematopoietic stem cells: the immunological perspective

Although stem cell mobilization has been performed for more than 20 years, little is known about the effects of mobilizing agents on apheresis composition and the impact of graft cell subsets on patients' outcome. With the increasing use of plerixafor and the inclusion of poor mobilizers in autologous transplant procedures, new parameters other than CD34(+) stem cell dose are emerging; plerixafor seems to mobilize more primitive CD34(+)/CD38(-) stem cells compared with G-CSF, but their correlation with stable hematopoietic engraftment is still obscure. Immune recovery is as crucial as hematopoietic reconstitution, and higher T and natural killer cells infused within the graft have been correlated with better outcome in autologous transplant; recent studies showed increased mobilization of immune effectors with plerixafor compared with G-CSF, but further data are needed to clarify the clinical impact of these findings. In the allogeneic setting, much evidence suggests that mobilized T-cell alloreactivity is tempered by G-CSF, probably with the mediation of dendritic cells, even though no clear correlation with GVL and GVHD has been found. Plerixafor is not approved in healthy donors yet; early data suggest it might mobilize a GVHD protective balance of immune effectors, but further studies are needed to define its role in allogeneic transplant.

Lymphocyte subset analysis for the assessment of treatment-related complications after autologous stem cell transplantation in multiple myeloma

BACKGROUND AIMS

The aim of this study was to investigate the correlation between infused lymphocyte populations and lymphocyte subsets at engraftment, and the early clinical implications of lymphocyte subset recovery after autologous stem cell transplantation (ASCT) in multiple myeloma (MM).

METHODS

We examined the lymphocyte populations of infused autografts and the lymphocyte subsets of peripheral blood at engraftment from 50 patients using flow cytometry. Each subset was grouped as low (below median) and high (above median) to examine the correlation with mucositis of grade 3 or more and the occurrence of infections and cytomegalovirus (CMV) reactivation.

RESULTS

Using Spearman correlation coefficients, we found that cell doses of infused CD8(+) (P = 0.042) and CD19(+) cells (P = 0.044) were significantly associated with the absolute lymphocyte count (ALC) at engraftment. The dose of infused CD34(+) cells was not associated with the change of lymphocyte subsets except for an inverse correlation with CD4(+) cells (P = 0.006). After adjusting for potential variables in univariate analysis, multivariate analyzes revealed that the lower ratio of infused CD4(+) to CD8(+) cells (P = 0.030) was an independent factor for severe mucositis. Of lymphocyte subsets at engraftment, a higher frequency of CD3(+) (P = 0.024) and a lower frequency of CD56(+) (P = 0.020) were independent predictors for infections after engraftment. A higher frequency of CD8(+) cells (P = 0.041) and a lower ratio of CD4(+) to CD8(+) (P = 0.021) were independent predictors for CMV reactivation.

CONCLUSIONS

Our data suggest that lymphocyte subset analysis of infused autograft and peripheral blood at engraftment may provide new predictors for early complications after ASCT in patient with MM.

Mobilisation strategies for normal and malignant cells

This review evaluates the latest information on the mobilisation of haemopoietic stem cells for transplantation, with the focus on what is the current best practice and how new understanding of the bone marrow stem cell niche provides new insights into optimising mobilisation regimens. The review then looks at the mobilisation of mesenchymal stromal cells, immune cells as well as malignant cells and what clinical implications there are.

CD4(+) CD28(+) lymphocytes on day 5 after high-dose melphalan for multiple myeloma predict a low risk of infections during severe neutropenia and are associated with the number of reinfused T lymphocytes of the autologous stem cell graft

BACKGROUND AIMS

Neutropenia following high-dose chemotherapy is associated with a substantial risk of infectious complications. The aim of this study was to identify variables in residual leukocyte subsets during neutropenia that are predictive for neutropenic fever.

METHODS

Residual leukocytes in the peripheral blood on day 5 after autologous blood stem cell transplantation were analyzed by three-color flow cytometry in 55 consecutive patients with multiple myeloma. Furthermore, the number of T cells transfused with the autografts was determined.

RESULTS

Neutrophil counts at day 5 and neutrophil engraftment were similar in patients with and without neutropenic fever. Low absolute lymphocyte, CD4(+) CD28(+) and CD45RO(+) CD28(+) counts at day 5 were associated with neutropenic fever. T-cell counts at day 5 correlated with the CD3(+) cell number in the graft.

CONCLUSIONS

Our data show that the absolute lymphocyte, CD4(+) CD28(+) and CD45RO(+) CD28(+) counts play a role in host defense during severe neutropenia. The T-cell number in the graft may help to identify patients at high risk of neutropenic infections.

Increased mobilization and yield of stem cells using plerixafor in combination with granulocyte-colony stimulating factor for the treatment of non-Hodgkin's lymphoma and multiple myeloma

Multiple myeloma and non-Hodgkin’s lymphoma remain the most common indications for high-dose chemotherapy and autologous peripheral blood stem cell rescue. While a CD34+ cell dose of 1 × 10⁶/kg is considered the minimum required for engraftment, higher CD34+ doses correlate with improved outcome. Numerous studies, however, support targeting a minimum CD34+ cell dose of 2.0 × 10⁶/kg, and an “optimal” dose of 4 to 6 × 10⁶/kg for a single transplant. Unfortunately, up to 40% of patients fail to mobilize an optimal CD34+ cell dose using myeloid growth factors alone. Plerixafor is a novel reversible inhibitor of CXCR4 that significantly increases the mobilization and collection of higher numbers of hematopoietic progenitor cells. Two randomized multi-center clinical trials in patients with non-Hodgkin’s lymphoma and multiple myeloma have demonstrated that the addition of plerixafor to granulocyte-colony stimulating factor increases the mobilization and yield of CD34+ cells in fewer apheresis days, which results in durable engraftment. This review summarizes the pharmacology and evidence for the clinical efficacy of plerixafor in mobilizing hematopoietic stem and progenitor cells, and discusses potential ways to utilize plerixafor in a cost-effective manner in patients with these diseases.

Current status of stem cell mobilization

New advances in effective mobilization of peripheral blood stem cells have permitted a greater proportion of patients to benefit from autologous stem cell transplantation. In this review, the relative merits of peripheral blood and mobilized bone marrow are discussed. All available agents are reviewed. A critical assessment of the appropriate dosing and frequency of available growth factors is undertaken, and the most commonly used chemotherapy plus growth factor combinations are covered. Specific recommendations for patients who are poor mobilizers are dealt with including the role of plerixafor.

Autograft mediated adoptive immunotherapy of cancer in the context of autologous stem cell transplantation

The infused stem cell autograft in autologous stem cell transplantation (ASCT) has been viewed mainly as hematologic rescue from the myelosuppressive side effect of conditioning regimens. However, recent reports have shown that the immune effector cells collected at the same time as the stem cells can produce an autologous graft-versus-tumor effect, similar to the graft-versus-tumor effect seen in allogeneic stem cell transplantation without the detrimental effects of graft-versus-host disease. In this article, we review the different immune effector cells collected and infused from the stem cell autograft and their association with clinical outcome post-ASCT, suggesting that ASCT can be viewed not only as a therapeutic maneuver to recover bone marrow function after deliver high-dose chemotherapy, but also as an adoptive immunotherapeutic intervention capable of eradicating residual tumor cells in patients with cancer.