Haploidentical stem cell transplantation-bone marrow vs peripheral blood

Hematopoietic stem cells may be obtained by collection of bone marrow, mobilization and collection of peripheral blood stem cells or umbilical cord blood. Transplantation of peripheral blood hematopoietic cells has increased due to faster engraftment and practicability in both the related, unrelated or haploidentical setting. We reviewed the question of which stem cell source - bone marrow (BM) or peripheral blood (PBSC) - is the most suitable for individuals undergoing haploidentical stem cell transplantation. BM or PBSC could be safely used as allograft sources for haploidentical transplantation with good outcomes and acceptable rates of GVHD and graft failure. Prospective randomized studies are needed to evaluate the effect of PB vs BM in haploidentical settings.     

Peripheral Blood or Bone Marrow Stem Cells? Practical Considerations in Hematopoietic Stem Cell Transplantation

Although peripheral blood stem cells (PBSC) have worldwide become the predominant source of progenitor cells for hematopoietic stem cell transplantation (HSCT), debate about their role compared with bone marrow (BM) has recently intensified, in large part based on the results of a multicenter Clinical Trials Network study which showed lower incidence of chronic graft-versus-host disease (cGVHD) and improved quality of life in recipients of myeloablative HLA-matched unrelated BM compared with PBSC transplants. However, in certain patient populations, PBSC may lead to improved clinical outcomes due to faster hematologic recovery, a lower risk of graft failure, and possibly a lower probability of relapse. This review will provide a comprehensive summary of studies comparing PBSC with BM as the graft source in terms of acute and chronic GVHD incidence, time to engraftment, and disease-free and overall survival probabilities after HLA-matched related and unrelated donor transplantation and haploidentical donor transplantation. Recommendations based on these studies regarding the use of PBSC versus BM for HSCT are offered.     

The risk of tumor cell contamination in peripheral blood stem cell collections.

Peripheral blood stem cell (PBSC) reinfusions are being used with increasing frequency in lieu of, or in addition to, autologous bone marrow transplantation (ABMT) to rescue cancer patients from the myeloablative effects of high-dose chemotherapy. However, the incidence and quantity of tumor cell contamination in PBSC collections has not been widely investigated. This paper reviews the existing data and presents new information to demonstrate that tumor cells are detectable in PBSC harvests from patients with a variety of malignancies. Furthermore, their presence in peripheral blood may have prognostic and clinical significance. Areas of future research and applications for PBSC technologies are also discussed.     

ABO血型不合供者外周血造血干细胞的采集及移植效果研究

目的探讨应用CS-3000 Plus血细胞分离机采集ABO血型不合供者外周血造血干细胞的效率及不去除红细胞和/或血浆进行异基因外周血造血干细胞移植(PBSCT)的安全性。方法经G-CSF 5μg/(kg.d)动员的异基因外周血干细胞供者33名,应用CS-3000 Plus血细胞分离机的干细胞采集程序于动员后d 5采集,其中ABO血型主要不合12名,次要不合8名以及ABO血型相合13名。根据供者外周血的红细胞压积(Hct)和单个核细胞(MNC)计数,对分离机参数作相应调整。输注前从产品袋中留取干细胞,检测有核细胞数、MNC比例、CD34+细胞数、红细胞、血浆含量。单次处理循环血量(9 986±2 489)ml,抗凝剂用量(971±162)ml。供者采集前注射10%葡萄糖酸钙,以预防低钙反应。观察PBSC输注后受者的生命体征、尿液颜色及是否有溶血相关不良反应等。结果ABO血型主要不合组、次要不合组与ABO血型相合组采集物中的有核细胞数、CD34+细胞数、MNC比例无统计学差异(P>0.05),3组供者每次采集的PBSC产品终体积近60 ml,ABO主要不合组采集物中混入红细胞为(3.67—10.25)×1010/袋,ABO次要不合组采集物中血浆量为22—38 ml,不去除红细胞及血浆,直接回输给受者,均未出现溶血反应,所有患者造血功能均获得重建。结论应用CS-3000 Plus血细胞分离机采集ABO血型不合供者的外周血干细胞,通过调整分离机参数,减少ABO血型不合红细胞的混入,可以获得足够的干细胞数量并安全用于移植。     

The role of pegfilgrastim in mobilization of hematopoietic stem cells.

Granulocyte colony-stimulating factors (G-CSF) are established prerequisites for the mobilization of peripheral blood stem cells (PBSC). Pegylated filgrastim (pegfilgrastim) has a substantially increased elimination half-life due to decreased serum clearance. A single-dose of pegfilgrastim is equivalent in enhancing neutrophil recovery after chemotherapy compared to daily filgrastim administrations. Several clinical trials also investigated chemotherapy plus single-dose pegfilgrastim in the mobilization of autologous PBSC in patients with lymphoma or myeloma. The results indicated similar efficacy compared to unconjugated G-CSF in terms of blood CD34+ cell count, stem cell yields as well as engraftment of after reinfusion. However, the number of patients in these trials were limited and there were non-randomized controls only. Furthermore, the mobilization of 12 mg pegfilgrastim was not superior over the 6 mg dose, and in one trial insufficient results were observed in heavily pretreated patients. In allogeneic stem cell donors a single-dose of 12 mg pegfilgrastim has been shown to induce a sufficient increase of blood CD34+ cells with a similar kinetics as known from conventional G-CSF. Adequate numbers of PBSC for transplantation could be harvested mostly by a single apheresis. Bone pain and headaches appeared to be more severe and about 90% of donors required analgetics. Additional concerns are due to spleen enlargement and hyperleukocytosis. Promising insights were reported from preclinical studies which revealed a modulating impact on both graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL) effect after transplantation of pegfilgrastim mobilized PBSC. Further trials are needed which carefully evaluate the issues of donor safety, but also the impact on graft composition and recipients' outcome.     

Stem cell procurement and transplantation in paediatric patients

Harvesting of peripheral blood stem cells (PBSC) with cell separators has become a safe procedure used in many centers. However, when PBSC harvesting in small children is considered, problems due to the small volume, loss of protein and red cell trapping arise. Priming the tubing of the cell separator with either albumin or red cells is necessary in children with a blood volume of less than 1500 mL. Ten children aged from 0.8 to 5 years underwent PBSC-apheresis without major problems despite low blood volume. Forty-one children with various malignancies had a total of 189 PBSC-aphereses with a median of 5 phereses for an individual patient. Harvesting of PBSC was started after recovering from neutropenia following scheduled chemotherapy. An average of 3.7 x 10(4)/kg CFU-GM per child was harvested. Sustained engraftment after myeloablative chemotherapy could be achieved when the dose of the retransfused PBSCs was greater than 3 x 10(4)/kg. Long-lasting complete remission was observed in 5 out of 25 patients.     

Validation of short‐term handling and storage conditions for marrow and peripheral blood stem cell products

BACKGROUND: Allogeneic hematopoietic stem cell transplants from unrelated donors are routinely used in the treatment of patients with hematologic malignancies. These cellular products are often collected off‐site and require transport from the collection site to transplantation centers. However, the effects of transport conditions and media on stem cell graft composition during short‐term storage have not been well described. STUDY DESIGN AND METHODS: Five bone marrow (BM), four filgrastim‐mobilized peripheral blood stem cell (PBSC), and four nonmobilized peripheral blood mononuclear cell (PBMNC) products were collected from healthy volunteer donors and stored at 4 or 20°C for up to 72 hours in 10% PlasmaLyte A plus anticoagulants such as 10% acid citrate dextran‐A (ACD‐A) and/or 10 IU/mL heparin. Products were evaluated at 0, 24, 48, and 72 hours for cellular content, viability, and metabolic activities. RESULTS: BM products maintained equivalent cell viability when stored at either 4 or 20°C over 72 hours, but cell viability was better maintained for PBSC products stored at 4°C. The mean viable CD34+ cell recovery for PBSC and BM products stored over 72 hours at 4°C was higher than 75%. Significantly lower CD34+ cell and colony‐forming unit recoveries were seen in PBSC products but not BM products stored at room temperature. Faster lactic acid accumulation was observed in PBMNC and PBSC products stored without ACD‐A. CONCLUSIONS: Seventy‐two‐hour storage of BM, PBSC, and PBMNC products at refrigerated temperature maintains optimal cell viability and recovery. Anticoagulation with ACD‐A is preferred over heparin to reduce lactic acid accumulation in the product media.     

The impact of peripheral blood stem cell transplants (PBSCT) on platelet usage

Peripheral blood stem cells (PBSC) are rapidly replacing bone marrow cells for autologous transplantation. This introduction, largely without randomized prospective trials, has occurred because of the ease of PBSC collection and the associated rapid haematological recovery with its lower costs and reduced blood product exposure. The administration of haematopoietic growth factors during recovery from high-dose chemotherapy increases the number of circulating haematopoietic progenitor cells to levels 1000-fold greater than levels normally found in blood. The CD34+ cell number, CFU-GM and CFU-Meg are commonly employed parameters used to assess the quality of PBSC harvests. This review examines the impact that PBSCT has had on haematological practice and patient care illustrated by our local practice in Cardiff.     

Factors influencing the timing of peripheral blood stem cell collection (PBSC)

High-dose conditioning regimens followed by autologous peripheral blood stem cell rescue are frequently used for the treatment of solid tumors and hematological malignancies. In 24 patients up to four peripheral stem cell collections (PBSC) were performed after priming with various chemotherapies and G-CSF (300 micrograms s.c. per day). In 16 patients (group A) more than 2 x 10(6) CD 34 positive cells per kg bodyweight could be collected; fewer were harvested in the remaining eight patients (group B). The amount of collected CD 34 positive cells correlated with the median number of these cells in the peripheral blood at the start of PBSC. The two groups differed both in recovery time after priming-induced cytopenia (4 vs 6 days from nadir) and in the number of WBC (21 x 10(6) mL-1 vs 6.1 x 10(6) mL-1) and platelets (133 x 10(6) mL-1 vs 58 x 10(6) mL-1) reached at first day of PBSC. No difference between the two groups was seen according to age, duration of disease or disease status. However, the intensity of prior treatment was significantly greater in group B than in group A. These observations indicate that the toxicity of previous chemotherapy is the most important factor for the mobilization of sufficient CD 34 positive cells into the peripheral blood.     

Application of peripheral blood stem cells (PBSC) mobilized by recombinant human granulocyte colony stimulating factor for allogeneic PBSC transplantation and the comparison of allogeneic PBSC transplantation and bone marrow transplantation.

Recombinant human granulocyte colony stimulating factor (rhG-CSF)-mobilized peripheral blood stem cells (PBSC) are now widely used for allogeneic PBSC transplantation (alloPBSCT). Large numbers of hematopoietic progenitor cells mobilized by rhG-CSF would be considered equivalent or better than bone marrow (BM) cells and would be used as an alternative to BM for allogeneic hematopoietic stem cell transplantation. The complications associated with the administration of rhG-CSF and apheresis in PBSC collection in formal donors are well tolerated and usually acceptable in the short term but some hazardous adverse events such as splenic rupture and cardiac arrest are reported although the incidence is very low. Protective means and stopping rules for safe donation in the collection of PBSC are established. The characteristics of PBSC were clarified; the expression of some adhesion molecules such as CD49d on CD34 positive cells of PBSC have been shown to be low compared to BM stem cells. In alloPBSCT compared with allogeneic BM transplantation (alloBMT), the incidence and frequency of graft versus host disease (GVHD) is of concern because high number of T lymphocytes are infused in alloPBSCT. The incidence and severity of acute GVHD are not increased but chronic GVHD is higher in alloPBSCT compared with alloBMT. The outcome of alloPBSCT and BMT are almost equivalent and conclusive results regarding survival are not yet available.     

Peripheral blood stem cells differ from bone marrow stem cells in cell cycle status,repopulating potential,and sensitivity toward hyperthermic purging in mice mobilized with cyclophosphamide and granulocyte colony-stimulating factor

Peripheral blood stem cells (PBSCs) are increasingly used in autologous stem cell transplantations. We investigated the mobilizing effect of a combined cyclophosphamide (CTX) and granulocyte colony-stimulating factor (G-CSF) treatment on progenitor cells (STRA) and primitive stem cells (LTRA) in normal and splenectomized CBA/H mice. This combined treatment not only resulted in mobilization but also in expansion of hematopoietic stem cell subsets. The latter phenomenon was somewhat suppressed in splenectomized animals, but in these mice an enhanced mobilization of STRA and LTRA cells into the peripheral blood was observed. Furthermore, we studied the engraftment potential of mobilized PBSCs. Mice transplanted with PBSCs engrafted significantly better compared to mice transplanted with bone marrow stem cells from control and mobilized mice. The repopulation curve was characterized by a less-deep nadir indicating that the differences occur during the initial phase after transplantation. Contamination of autologous PBSC transplants with malignant cells is noticed frequently and is the basis for urging the use of purging modalities. Here we used hyperthermia and found that the mobilized progenitor cells in peripheral blood are more resistant to hyperthermia than those in the bone marrow (i.e., a survival of 11 +/- 5% after 90 min at 43 degrees C for peripheral blood progenitors, compared to 0.5 +/- 0.4% in bone marrow of mobilized animals and 1.6 +/- 0.5% in normal animals, respectively). Hyperthermic purging does not eliminate the superior repopulating features of a PBSC graft, as is demonstrated by an increased median survival time of lethally irradiated mice transplanted with purged PBSCs. In conclusion, our data demonstrate that CTX + G-CSF-mobilized PBSCs have an enhanced engraftment potential concomitantly with a decreased cycling activity and hence a decreased hyperthermic sensitivity. These findings support the use of these mobilized PBSCs for autologous stem cell transplantation and strengthen the basis for using hyperthermia as a purging modality.     

Peripheral blood stem cell collection and transplantation using the Haemonetics Multi Component System

AIM: To assess clinical usefulness of an intermittent-flow blood cell separator in peripheral blood stem cell (PBSC) collection and transplantation. RESULTS: The Haemonetics Multi Component System (Multi) was used to collect PBSC (52 aphereses in 17 patients). The mean processing blood volume and the mean PBSC yield were 7407 ml and 2.16 x 10(6) CD34+ cells/kg, respectively. When CD34+ cells exceeded 0.3% of the peripheral WBC, more than 2.0 x 10(6) CD34+ cells/kg could be collected by a single apheresis. Eight patients underwent PBSC transplantation after high-dose chemotherapy. Hematopoietic recovery was achieved in a median period of 10 days. CONCLUSIONS: (1) A single-arm, light-weight machine has sufficient capability to collect PBSC. (2) The percentage of CD34+ cells in the peripheral WBC is a good predictor of the CD34+ cell yield of the collection.     

Seasonal variation of human physiology does not influence the harvest of peripheral blood CD34+ cells from unrelated hematopoietic stem cell donors

There are many reports on factors predicting the outcome of PBSC (peripheral blood stem cell) mobilization, such as the donor’s gender, age, weight, white blood cell count, platelets pre apheresis, LDH and iron status. Although there are reports of seasonal variation in the physiology of the human immune system and hematopoiesis there are no data that such differences play a role in the response to G-CSF in healthy hematopoietic stem cell donors. The response to G-CSF could also impact the collection results during different seasons. To assess the possible impact of seasonal variation we performed a retrospective, single-center analysis of mobilization and harvest of PBSC in 330 healthy unrelated donors. We found no significant differences in the number of CD34+ cells in peripheral blood after G-CSF mobilization and in collection results when all donors were analyzed. In the subgroup of male donors the number of CD34+ stem cells after G-CSF mobilization was higher than average in summer and autumn (p = 0.036), however, it did not translate into clinically relevant differences in stem cell harvest.We conclude that although there is possible seasonal variation in the response to G-CSF in male donors there is no impact on PBSC harvest in healthy unrelated donors.     

Plerixafor plus G-CSF in combination with chemotherapy for stem cell mobilization in a pediatric patient with Ewing's sarcoma

Some malignant tumors in childhood require high‐dose chemotherapy with stem cell support to achieve a cure. In patients heavily pretreated with myelosuppressive chemotherapy or irradiation, granulocyte colony‐stimulating factor (G‐CSF) may fail to mobilize stem cells from the bone marrow. Based on the experience with lymphoma and myeloma patients in whom peripheral blood‐derived stem cell (PBSC) collection following mobilization with G‐CSF failed, we successfully employed plerixafor in a 14‐year‐old female diagnosed with Ewing's sarcoma in early relapse treated with three lines of chemotherapy in whom PBSC could not be mobilized using either G‐CSF alone or G‐CSF following chemotherapy. No side effects were observed. Plerixafor may be an effective and safe agent for stem cell collection in pediatric patients with solid tumors, although new studies addressed to evaluate its effectiveness and safety are needed. J. Clin. Apheresis 27:260–262, 2012. © 2012 Wiley Periodicals, Inc.     

Evaluation of the Sysmex XN automated hematopoietic progenitor cell enumeration for timing of peripheral blood stem cell harvest

BackgroundEnumeration of stem cells is essential in the management of peripheral blood stem cell (PBSC) harvest. An alternative to the gold standard flow cytometric CD34+ stem cell count is the fully automated hematopoietic stem cell (HPC) count on the Sysmex XN hematology analyzer.Materials and methodsEighty-nine patients and healthy stem cell donors who underwent PBSC harvest were included in the study. Stem cells were enumerated in pre-harvest peripheral blood and the apheresis yield by both flow cytometric CD34+ stem cell enumeration and by the Sysmex XN HPC count.ResultsThe Sysmex HPC concentration overestimated the CD34+ stem cell concentration by a ratio of 1.3 in average. The agreement between the two methods was poor at concentration <40 stem cells/μL (Bias: 45 %, 95 % limits of agreement: -71 - 160 %). CD34+ stem cell concentration and HPC concentration correlated well in pre-harvest peripheral blood (R=0.73, slope=0.96). We established a positive cut off >43.5 HPC/μL, where PBSC harvest can be initiated. And a negative cut off <16.5 HPC/μL, where harvest should be postponed or other mobilizing regimens or bone marrow harvest should be considered. 33 % of measurements were in between the negative and positive cut-off and would require a supplementary CD34+ cell count.ConclusionAlthough Sysmex HPC count correlates well with CD34+ cell count in peripheral blood, the agreement between the two methods is poor, especially at low concentrations, namely in the clinical decision range. Sysmex HPC count as a surrogate for CD34+ cell count should, therefore, be used with caution.     

Hematopoietic progenitor cell count, but not immature platelet fraction value, predicts successful harvest of autologous peripheral blood stem cells

Mobilized stem cells in the peripheral blood (PB) must be efficiently harvested at the appropriate time before autologous PB stem cell (PBSC) transplantation. Enumeration of CD34+ cells in the PB before apheresis predicts the number of PBSCs that can be collected, but the cytometric techniques used are complex and expensive. Therefore, it is necessary to identify an alternative to the CD34+ cell count in PBSC harvest-time monitoring. Fully automated flow cytometry using blood cell counters now allows reliable quantification of immature myeloid cells in the PB, referred to as hematopoietic progenitor cells (HPC), and reticulated platelets, expressed as the immature platelet fraction (IPF). Immature or reticulated platelets are thought to correlate with thrombopoietic activity of the marrow. Following a chemotherapy nadir, the recovery of white blood cell and platelet counts has been used to determine the right time for apheresis. Therefore, we examined whether the HPC count and IPF value could be used to predict PBSC mobilization in 20 patients with hematological malignancies. The HPC count was found to be correlated with the CD34+ cell count (r = 0.84, P < 0.01), whereas the IPF value was not (r = 0.37, P = 0.44). Therefore, the HPC count, but not the IPF value, is a possible predictor of the timing of autologous stem cell transplantation.     

CD34+ cell enrichment for autologous peripheral blood stem cell transplantation by use of the CliniMACs device

Several devices for selection of CD34+ peripheral blood stem cells (PBSC) have been used during the last years for reducing tumor cell contamination of the graft. The new CliniMACS system (magnetic-activated cell separation system by Miltenyi Biotech GmbH, Bergisch-Gladbach, Germany) was recently approved for clinical use in Europe. To evaluate its purging efficiency and engraftment data in the autologous transplant, PBSC from 28 adult patients with various malignant diseases (non-Hodgkin's lymphoma, n = 17; chronic lymphocytic leukemia, n = 5; multiple myeloma, n = 4; acute lymphocytic leukemia, n = 1; medulloblastoma, n = 1) were mobilized by chemotherapy and granulocyte colony-stimulating factor (G-CSF) (10 microg/kg per day). Thirty leukapheresis products from 28 patients with a median of 4.4 x 10(8) nucleated cells/kg body weight (bw)(range 0.6-10.8 x 10(8)/kg bw) and a median of 7.1 x 10(6) CD34+ cells/kg bw (range 2.8 to 18.8 x 10(6)/kg bw) were selected using the Cobe spectra cell separator (Cobe BCT Inc., Lakewood, CO). After the CliniMACS procedure, the median yield of CD34+ selected cells was 4.5 x 10(6)/kg (range 2.2-11.1 X 10(6)/kg bw) with a median recovery of 69.5% (range 46.9-87.3%) and a median purity of 97.7% (range 89.4-99.8%). The procedure did not alter viability of selected cells, which was tested by propidium iodide staining. So far, purified PBSC were used for autologous transplantation in 15 out of 28 patients after total body irradiation and/or high-dose chemotherapy. Median time to reach an absolute neutrophil count > 500/microl was 12 days (range 10-18 days), platelet recovery >50,000/microl occurred at day + 16 (range 11-22). With a median follow-up time of 12 months (range 3-19), 5 patients died of relapse. We confirmed the feasibility and safety of the CliniMACS CD34+ cell enrichment procedure in adult patients with autologous PBSC transplantation.     

Optimal timing for the collection and in vitro expansion of cytotoxic CD56(+) lymphocytes from patients undergoing autologous peripheral blood stem cell transplantation

To identify the optimal time for the collection of CD56(+) cytotoxic lymphocytes for adoptive immunotherapy in patients undergoing high-dose chemotherapy (HDCT) and peripheral blood stem cell (PBSC) transplantation, 18 breast cancer patients receiving either three cycles of epirubicin/paclitaxel (CT x 3) followed by HDCT and PBSC transplantation (n = 12) or CTx6 (n = 6) were studied. Blood samples were obtained before each CT/HDCT cycle, from PBSC collections, and repeatedly after autografting for up to 12 months. The number of CD56(+)3(-) and CD56(+)3(+) lymphocytes, their in vitro expandability with interleukin-2, and their cytotoxicity against MCF-7 and Daudi cells were analyzed. Six healthy females served as controls. CD56(+) cell counts in both treatment groups were subnormal but stable during the observation period. The cytotoxicity of the expanded CD56(+) cells was normal and unaffected by the treatment. The in vitro CD56(+) cell expandability (controls, 100 +/- 31-fold, mean +/- SEM) was normal before CT1 and CT2, but reduced in PBSC harvests performed after CT2 and application of G-CSF (21 +/- 6-fold; p < 0.01). After PBSC harvesting, the CD56(+) cell expandability increased to 185 +/- 74-fold and 170 +/- 69-fold (before CT3 and HDCT). This increase was not observed in those patients who did not undergo PBSC mobilization. Two weeks after autografting, the CD56(+) cell expandability was minimal (6 +/- 1-fold), and recovered to 34 +/- 6-fold. Thus, CT, HDCT and autografting do not alter the frequency and inducible cytotoxicity of CD56(+) cells in breast cancer patients. However, the proliferative capacity of CD56(+) cells obtained from PBSC harvests and after autografting is impaired. Therefore, instead of the PBSC graft, maximally expandable CD56(+) cells obtained at least 1 week after PBSC collection should be considered for adoptive immunotherapy after PBSC autografting.     

Management strategies for poor peripheral blood stem cell mobilization.

Peripheral blood stem cells (PBSC) have nearly replaced bone marrow (BM) as the preferred source of hematopoietic rescue for patients undergoing high-dose chemotherapy. However, some patients fail to mobilize sufficient numbers of PBSC into the peripheral blood thereby putting high-dose chemotherapy at risk. The present article reviews mobilization of PBSC with a special focus on poor mobilizers. Under steady-state conditions less than 0.05% of the white blood cells (WBC) are CD34+ cells. Chemotherapy results in a 5-15-fold increase of PBSC. Combining chemotherapy and growth factors increases CD34+ cells up to 6% of WBC. Several factors affect the mobilization of PBSC: age, gender, type of growth factor, dose of the growth factor and in the autologous setting patient's diagnosis, chemotherapy regimen and number of previous chemotherapy cycles or radiation. Poor mobilizers are defined as patients with less than 10 CD34+ cells/mul in the peripheral blood during mobilization. Promising approaches for those patients rely on remobilization, use of high doses of granulocyte-colony stimulating factor (G-CSF), or the combination of G-CSF and granulocyte macrophage (GM)-CSF, which successfully mobilized the majority of poor mobilizing patients. New agents such as long lasting variants of G-CSF and CXCR4 antagonists are at the horizon and studied in clinical trials as mobilizing agents. Muscle and bone pain are frequent adverse events in stem cell mobilization but are usually tolerated under the use of analgesics. Large volume apheresis (LVL) with a processed volume of more than 4-fold patient's blood volume is an approach to increase the CD34+ yield in patients with low CD34+ pre-counts resulting in higher yields of CD34+ cells for transplantation. Processing of more blood in LVL is achieved by an increase of the blood flow rate and an altered anticoagulation regimen with the occurrence of more citrate reactions.     

Peripheral blood stem cell mobilization for high-dose chemotherapy.

Several studies have clearly documented a more rapid hematopoietic recovery with growth factor-mobilized PBSC than with bone marrow. Time to engraftment for neutrophils and platelets average 8-12 days in contrast to 2-4 weeks after bone marrow. This rapid hematopoietic recovery with PBSC has decreased the duration of hospitalization, transfusion requirements, and costs. Although growth factors alone may mobilize enough PBSC for high-dose chemotherapy, administration of growth factor after submyeloablative chemotherapy increases the yield of CD34+ cells. Based on the current data, CD34+ cell content of PBSC appears to be the single most powerful predictor of hematopoietic recovery. Infusion of > or =5 x 10(6) CD34+ cells/kg is associated with a rapid engraftment of neutrophils and platelets, although successful engraftment has also been reported with infusion of 2.5-5 x 10(6) CD34+ cells/kg. Age, prior radiotherapy, marrow involvement, and prior chemotherapy regimens are important factors influencing the yield of stem cells. Therefore, using these pa-rameters, we may identify the patients who will fail to mobilize sufficient numbers of PBSC before collection and use new strategies for stem cell mobilization. Because of the ease of collection and rapid engraftment after myeloablative therapy, PBSC have replaced bone marrow for autologous transplantation and may supplant bone marrow for allogeneic transplantation in the near future.