A comparison of CD34+ cell selected and unselected autologous peripheral blood stem cell transplantation for multiple myeloma: a case controlled analysis

Optimized processing of growth factor mobilized peripheral blood CD34+ products by counterflow centrifugal elutriation

Cell separation by counterflow centrifugal elutriation has been described for the preparation of monocytes for vaccine applications, but its use in other current good manufacturing practice (cGMP) operations has been limited. In this study, growth factor-mobilized peripheral blood progenitor cell products were collected from healthy donors and processed by elutriation using a commercial cell washing device. Fractions were collected for each product as per the manufacturer's instructions or using a modified protocol developed in our laboratory. Each fraction was analyzed for cell count, viability, and blood cell differential. Our data demonstrate that, using standard elutriation procedures, >99% of red blood cells and platelets were removed from apheresis products with high recoveries of total white blood cells and enrichment of CD34+ cells in two of five fractions. With modification of the basic protocol, we were able to collect all of the CD34+ cells in a single fraction. The CD34-enriched fractions were formulated, labeled with a ferromagnetic antibody to CD34, washed using the Elutra device, and transferred directly to a magnetic bead selection device for further purification. CD34+ cell purities from the column were extremely high (98.7 ± 0.9%), and yields were typical for the device (55.7 ± 12.3%). The processes were highly automated and closed from receipt of the apheresis product through formulation of target-enriched cell fractions. Thus, elutriation is a feasible method for the initial manipulations associated with primary blood cell therapy products and supports cGMP and current good tissue practice-compliant cell processing.

Infections after CD34-selected or unmanipulated autologous hematopoietic stem cell transplantation

Immune reconstitution may be delayed after CD34-selected compared with unmanipulated autologous peripheral blood stem cell transplantation (PBSCT), resulting in a theoretically increased risk of infections. In a case-control matched study we compared the incidence of infection in 25 recipients of CD34-selected PBSC (CD34 group) and 75 recipients of unmanipulated PBSC (PBSC group) transplants. The population included 52 males and 48 females suffering from non-Hodgkin's lymphoma (n = 32), Hodgkin's disease (n = 8), multiple myeloma (n = 40) or breast cancer (n = 20). Neutrophil engraftment was comparable in the two groups. The actuarial incidence of infection was similar in the two groups (56% vs. 49% at day 30, and 70% vs. 64% at 1 yr respectively). The proportion of patients with 1, 2 or 3 infections, the number of infectious event per patient (1.32 vs. 1.04; NS), the number of infections before day 15 or 30, between days 31 and 100 or after day 100, the risk of varicella-zoster virus or cytomegalovirus infection or disease, or the use of antibiotic or antifungal therapy, were not increased in the CD34 compared with the PBSC group. The main agents responsible for infection were bacteria, particularly gram-positive cocci, in both groups. Bacteremia accounted for 33% of all infectious events in the CD34 group vs. 16% in the PBSC group (P < 0.05). Fungal infections were rare. In conclusion, our results do not support the notion that CD34-selection of the graft is associated with an increased rate of infection after autologous PBSC transplantation. The role of extended infection prophylaxis should be evaluated.

Clinical applications of CD34+ cell-selected peripheral blood stem cells

Peripheral blood stem cells (PBSC) are increasingly used for stem cell transplantation after high dose chemotherapy. CD34+ cell selection has also been done for use in autologous transplantation studies Bone marrow (BM) may contain tumor cells at the time of harvesting, and on re-infusion, these cells could contribute to a subsequent relapse. Similarly, tumor cell contamination of PBSC collections has been found in a number of studies. Therefore, purging contaminating tumor cells may prevent cases of relapse. As most tumor cell types do not express CD34 antigen, one of the most widespread applications of CD34+ cell selection is likely to be in tumor cell purging. Similarly, CD34+ cell selection has aided allogeneic transplantation studies. Acute graft-versus-host disease (aGVHD) is a major cause of morbidity and mortality in cases of allogeneic transplantation. As aGVHD is mediated by donor T cells, removal of T cells from the graft by CD34+ cell selection may ensure prophylaxis against aGVHD. Further, high-dose immunosuppression followed by CD34+ cell-selected stem cell rescue is theoretically reasonable as a therapeutic tool for patients with autoimmune disease resistant to conventional therapy. However, patients given T cell-depleted transplantation have an increased risk of opportunistic infection as well as malignancies related to immunosuppression; therefore, close monitoring is warranted. We describe here clinical applications of CD34+ cell-selected PBSC for a variety of diseases, with special emphasis on the efficacy as well as drawbacks of this novel technique.

Significant and persistent loss of bone mineral density in the femoral neck after haematopoietic stem cell transplantation: long-term follow-up of a prospective study

Reduced bone mineral density (BMD) has been reported following allogeneic stem cell transplantation (alloSCT) but the effects of autologous SCT (autoSCT) are less well characterized. We performed a prospective study of BMD changes and its determinants in 44 SCT recipients (38 auto and six allo; 30 peripheral blood SCT and 14 bone marrow transplantation). Serial measurements of BMD at the lumbar spine and femoral neck were performed at baseline and at 3, 6, 12 and 24 months, and spinal radiographs were performed at baseline and 12 months. Mean baseline BMD values at the femoral neck and spine were within normal limits. At 3 months, there was a significant decline of BMD at the femoral neck (P = 0.011) and a non-significant trend towards reduction at the spine. BMD loss persisted for up to 2 years at the femoral neck (P = 0.005), but values returned to baseline at the spine. Reflecting the rapid initial decline in BMD, bone-specific alkaline phosphatase (a serum marker of bone formation) showed a significant initial decline at 1 month but had recovered to pretransplant levels by 3 months. No new fractures were detected at 1 year post transplant. Sex, diagnosis, use of total body irradiation, stem cell source and type of graft (auto versus allo) did not significantly predict BMD change over the first 12 months. In conclusion, significant and persistent bone loss at the femoral neck was demonstrated in this group of patients following stem cell transplantation. The implications of these findings for future fracture risk require further study.

Autologous blood cell transplantation in multiple myeloma: impact of CD34+ cell selection with long follow-up

Positive CD34(+) selection to purge blood cell harvests is one way to attempt to reduce the high relapse risk after high-dose chemotherapy (HDT) supported by autologous blood cell transplantation (ABCT) in patients with multiple myeloma (MM). Until recently, however, the impact of CD34(+) selection, if any, on long-term clinical outcome in MM has remained obscure. We have analyzed engraftment kinetics, response to HDT, progression-free survival (PFS), and overall survival (OS) for 64 consecutive MM patients who have been treated with up-front HDT plus ABCT at our institution between 1993 and 1998. Nonrandomized comparisons were made between transplants with unselected (39 patients) and CD34(+)-selected (25 patients) grafts. The engraftment kinetics, need of blood product support, discharge time from hospital, and response to HDT were similar for both unselected and selected transplants. The median PFS was also similar (26 and 30 months, respectively) for the both groups. With a median follow-up time for the survivors of 67.5 months, the median OS (78 and 75 months, respectively) did not differ between transplants with unselected and selected grafts. In conclusion, this nonrandomized study suggests that positive CD34(+) selection has no beneficial impact on long-term outcome of patients with MM.

The role of cytotoxic therapy with hematopoietic stem cell transplantation in the therapy of multiple myeloma: an evidence-based review

Evidence supporting the role of hematopoietic stem cell transplantation (SCT) in the therapy of multiple myeloma (MM) is presented and critically evaluated in this systematic evidence-based review. Specific criteria were used for searching the published medical literature and for grading the quality of the evidence, the strength of the evidence, and the strength of the treatment recommendations. Treatment recommendations based on the evidence presented in the review were made unanimously by a panel of MM experts. Recommendations for SCT as an effective therapy for MM include the following: SCT is preferred to standard chemotherapy as de novo therapy; SCT is preferred as de novo rather than salvage therapy; autologous peripheral blood stem cell transplantation (PBSCT) is preferred to bone marrow transplantation (BMT); and melphalan is preferred to melphalan plus total body irradiation as the conditioning regimen for autologous SCT. Recommendations that SCT is not effective include the following: current purging techniques of bone marrow. Recommendations of equivalence include the following: PBSCT using CD34+ selected or unselected stem cells. No recommendation is made for indications or transplantation techniques that have not been adequately studied, including the following: SCT versus standard chemotherapy as salvage therapy, tandem autologous SCT, autologous or allogeneic SCT as a high-dose sequential regimen, allogeneic BMT versus PBSCT, a preferred allogeneic myeloablative or non-myeloablative conditioning regimen, and maintenance therapy post-autologous SCT with interferon alpha post-SCT. The priority area of needed future research is maintenance therapy posttransplantation with nothing versus interferon alpha versus other agents such as corticosteroids or thalidomide or its derivatives.

Tumor cell contamination in re-infused stem cell autografts: does it have clinical significance?

Tumor cells frequently contaminate autologous stem cell products in patients having a variety of malignancies. Mobilized peripheral blood stem cells may be less contaminated with tumor cells than bone marrow harvests are, but they are still frequently infiltrated. Gene-marking studies using retroviral vectors provide evidence that tumor cells contained in autografts contribute to relapse in myeloid leukemia and neuroblastoma patients. Also clinical studies have shown that tumor cell contamination of autografts is associated with shortened disease-free survival; on the other hand, successful ex vivo purging of tumor cells is associated with superior clinical outcome. However, the presence of tumor cells in autografts or insufficient purging may correlate with the extent of systemic residual disease and/or tumor chemosensitivity; therefore, there is no direct evidence that reinfused tumor cells alone cause relapse. Particularly in patients having highly chemosensitive disease and no detected systemic residual disease following high-dose transplant chemotherapy, the relative number of tumor cells contained in autografts and eventually reinfused, may become a determining factor for clinical outcome. There are no randomized trials showing improved (disease-free) survival with purging. In the absence of such trials, the contribution of tumor cells in the stem cell autografts to subsequent relapse remains controversial.

Antibody responses to vaccinations given within the first two years after transplant are similar between autologous peripheral blood stem cell and bone marrow transplant recipients

As a consequence of the significantly larger inoculum of lymphoid cells present in peripheral blood stem cell (PBSC) harvests compared to bone marrow (BM), it is possible that autoPBSCT recipients may have an earlier and*or enhanced response to vaccines. Until data to confirm this become available, the European Blood and Marrow Transplantation Association (EBMT) recommend that all transplant recipients be immunized in the same way regardless of stem cell source. We performed a prospective study comparing serological responses to influenza, pneumococcal polysaccharide and tetanus toxoid vaccines between autoPBSCT with autoBMT recipients. Antibody responses in sibling HLA-matched allogeneic BMT (alloBMT) survivors were also evaluated. All vaccines were administered within the first 2 years after stem cell transplantation. Fifty patients were enrolled. The time of vaccination after transplant was similar between autoPBSCT (mean 11 months for each vaccine) and autoBMT recipients (mean 12 months except 13 months for tetanus toxoid) (P = NS). Serological responses were poor and no significant difference in response to any of the vaccines used was seen between the three transplant cohorts. We provide no evidence that current EBMT guidelines be modified. Large prospective vaccine studies are needed to address the issue more fully.

Results of high-dose treatment with autologous stem cell support in patients with multiple myeloma

The introduction of high-dose treatment (HDT) with autologous hematopoietic stem cell support in patients with multiple myeloma (MM), although curative in only a minority of patients, has led to significantly longer event-free (EFS) and overall survival (OS) and likely improved quality of life compared with conventional chemotherapy. However, several issues remain unsettled. We review the current knowledge with respect to transplantation-related controversies, such as intensity of cytoreductive therapy (single v tandem transplants), optimal timing of the procedure, and potential benefit of graft purging and posttransplant consolidation chemotherapy. Special emphasis is placed on the safety and efficacy of transplant in elderly patients and in those with impaired renal function, who are usually excluded from the most effective therapy.

Dexamethasone, paclitaxel, etoposide, cyclophosphamide (d-TEC) and G-CSF for stem cell mobilisation in multiple myeloma

Forty-one patients with multiple myeloma were treated with a novel stem cell mobilisation regimen. The primary end points were adequate stem cell mobilising ability (>1% circulating CD34-positive cells) and collection (> or = 4 x 10(6) CD34-positive cells/kg), and safety. The secondary end point was activity against myeloma. The regimen (d-TEC) consisted of dexamethasone, paclitaxel 200 mg/m(2) i.v., etoposide 60 mg/kg i.v., cyclophosphamide 3 g/m(2) i.v., and G-CSF 5-10 microg/kg/day i.v. A total of 84 cycles were administered to these 41 individuals. Patient characteristics included a median age of 53 years, a median of five prior chemotherapy cycles, and a median interval of 10 months from diagnosis of myeloma to first cycle of d-TEC. Seventy-five percent of the patients had stage II or III disease, 50% had received carmustine and/or melphalan previously, and 25% had received prior radiation therapy. Eighty-eight percent of patients mobilised adequately after the first cycle of d-TEC and 91% mobilized adequately after the second cycle. An adequate number of stem cells were collected in 32 patients. Of the remaining nine patients, three mobilised, but stem cells were not collected, two mobilised but stem cell collection was < 4 x 10(6) CD34-positive cells/kg, three did not mobilise, and one died of disease progression. Major toxicities included pancytopenia, alopecia, fever and stomatitis. One patient died from multi-organ failure and progressive disease. Fifty percent of evaluable patients demonstrated a partial response and 28.6% of patients had a minor response. This novel dose-intense regimen was safe, capable of stem cell mobilisation and collection, even in heavily pre-treated patients, and active against the underlying myeloma.

European Group for Blood and Marrow Transplantation Registry studies in multiple myeloma

The European Group for Blood and Marrow Transplantation (EBMT) Myeloma Registry, established in 1987, contains data on 1,368 allogeneic and more than 8,000 autologous stem cell transplants performed since 1983. Among autologous transplant patients, the median survival after transplantation is 50 months, and the actuarial survival at 10 years is 30%, with a plateau appearing at about 8 years. Factors of importance for a more favorable prognosis are lower age, response to chemotherapy, only one course of primary chemotherapy, stage I or II disease, and low beta(2)-microglobulin at diagnosis. Beneficial procedural factors associated with better outcome are a preparative regimen without total body irradiation (TBI), posttransplant interferon alfa maintenance treatment, and possibly tandem transplantation. In vitro graft purging, using CD34(+) selection, does not have any impact on survival. A case-matched analysis comparing autologous and allogeneic transplantation demonstrated significantly better survival in the former group, with median posttransplant survival times of 36 months and 18 months in the autologous and allogeneic groups, respectively. This result was in turn due to a markedly lower incidence of transplant-related death among the autotransplant patients: 13%, versus 41% for the allogeneic group. However, recent data on allogeneic transplants performed from 1994 to 1998 has demonstrated a decrease in treatment-mortality to 30%, and this has resulted in a prolongation of survival; in this analysis, the results are similar irrespective of the type of graft used, allogeneic bone marrow or blood stem cells. In a small case-matched analysis, transplantation with an identical twin donor was superior to both allogeneic and autologous transplantation with respect to survival and freedom from progression.

Lack of benefit of CD34+ cell selected over non-selected peripheral blood stem cell transplantation in multiple myeloma: results of a single center study

In order to determine the clinical impact of CD34+ cell selected autologous transplantation in multiple myeloma (MM), we have performed a retrospective case-controlled analysis comparing 21 MM patients receiving high-dose melphalan and autologous transplantation with CD34+ peripheral blood stem cells (PBSC) as front-line therapy to 21 control patients receiving unselected products. Case matching was performed using the following criteria: age and beta2-microglobulin at diagnosis and disease status at the time of transplantation. Both cohorts were homogeneous in term of induction treatment and conditioning regimen. Patients were collected for CD34+ selection after priming with G-CSF alone. Significantly fewer CD34+ cells/kg were infused to patients in the selected group as compared to patients in the control group: 2.2 (range 0.5-14.3) vs 9.4 (range 1.1-15) (P < 0.001). The median time to neutrophil recovery > or =0.05 x 10(9)/l was 10 days for the CD34+ group and 9.5 days for the control group (P = 0.357). The median time to platelet recovery > or = 20 x 10(9)/l was 9 days for the CD34+ group and 4.5 days for the control group (P = 0.005). Response rates were comparable in both groups (85.7% in the CD34+ group vs 90.4% in the control group). At 3 years, event-free survival (32% in the CD34+ group vs 39% in the control group) and overall survival (85% in the CD34+ group vs 79% in the control group) were not significantly different. Finally, use of unselected products dramatically reduced the cost of the transplantation procedure. This study shows that CD34+ cell selected autologous transplantation is more expensive than transplantation with unselected products and does not improve the clinical outcome of patients with MM.

Progress in haematopoietic stem cell transplantation for multiple myeloma

High-dose myeloablative treatment followed by autologous haematopoietic stem cell transplantation has significantly improved survival of patients younger than 65 years of age with multiple myeloma as compared with conventional chemotherapy. However, all patients seem to relapse and molecular remissions are rare. Results of allogeneic transplantation, still hampered by high transplant-related mortality, have improved dramatically over the last 5-6 years and this is an option for patients younger than 50-55 years old. The relapse rate is lower than with autologous transplantation and molecular remissions are frequent. Some patients are still in complete haematological remission more the 10 years following transplantation. Autologous transplantation followed by nonmyeloablative allogeneic transplantation is on trial and may be a way to eventually cure a fraction of younger patients with multiple myeloma.

CD34: to select or not to select? That is the question

Recent evidence suggests that expression of CD34 on the cell membrane does not always correlate with stem cell activity. In the mouse, there is a highly quiescent population of stem cells that lacks CD34 expression, but has full reconstituting capacity. The current review addresses the discovery of a similar population of dormant CD34-negative human hematopoietic stem cells. This information casts some uncertainty on the benefits of CD34+ cell isolation for stem cell transplantation, until more is known about the novel CD34-negative stem cell population. Methods designed to achieve removal of specific mature blood cell lineages might prove to be most advantageous in the future.