Large-volume leukapheresis in pediatric patients: processing more blood diminishes the apparent magnitude of intra-apheresis recruitment

Optimizing leukapheresis product yield and purity for blood cell-based gene and immune effector cell therapy

PURPOSE OF REVIEW

A critical common step for blood-based ex-vivo gene and immune effector cell (IEC) therapies is the collection of target cells for further processing and manufacturing, often accomplished through a leukapheresis procedure to collect mononuclear cells (MNCs). The purpose of this review is to describe strategies to optimize the apheresis product cell yield and purity for gene and IEC therapies. Relevant data from the conventional bone marrow transplant literature is described where applicable.

RECENT FINDINGS

Product yield is affected by three main factors: the peripheral blood concentration of the target cell, optimized by mobilizing agents, donor interventions or donor selection; the volume of peripheral blood processed, tailored to the desired product yield using prediction algorithms; and target cell collection efficiency, optimized by a variety of device and donor-specific considerations. Factors affecting product purity include characteristics of the donor, mobilizing agent, device, and device settings.

SUMMARY

Strategies to optimize product yield and purity for gene and IEC therapies are important to consider because of loss of target cell numbers or function with downstream steps and detrimental effects of nontarget cells on further manufacturing and patient outcome.

Mobilization kinetics of CD34+ hematopoietic stem cells stimulated by G-CSF and cyclophosphamide in patients with multiple sclerosis who receive an autotransplant

BACKGROUND AIMS

Autologous hematopoietic stem cell transplantation (AHSCT) is an alternative for multiple sclerosis (MS) patients who do not respond to conventional treatment. Mobilization kinetics of CD34+ cells in MS patients has not been studied.

METHODS

Patients with MS mobilized with granulocyte colony-stimulating factor (G-CSF) and cyclophosphamide (Cy) were prospectively studied. Three counts of CD34+ cells were done in peripheral blood: at baseline before mobilization, at the start, and immediately at the end of apheresis. Complete blood counts were performed at the times of CD34+ cell counting. Standard statistical descriptive analysis of MS patients' salient features was performed, and after log 10 transformation of the data, Pearson test was performed to assess correlation between variables and CD34+ cell count. In addition, multiple linear regression of relevant data was carried out for multivariate analysis.

RESULTS

Data of 51 consecutive MS patients with median age of 48 (31-64) years were analyzed. The CD34+ cell count increased 26-fold after mobilization. During large volume leukapheresis (LVL), the number of CD34+ cells in peripheral blood increased from 51.29 CD34+/μL at the start to 62.3 CD34+/μL at the end. A negative correlation between CD34+ cell count after leukapheresis and age (r = -0.32, P = 0.02) was observed. Neither the CD34+ baseline count nor sex correlated with the CD34+ count in peripheral blood immediately at the end of apheresis.

CONCLUSIONS

Mobilization with G-CSF and Cy in MS patients resulted in effective CD34+ hematoprogenitors release from the bone marrow and in intra-apheresis recruitment.

Large volume leukapheresis is efficient and safe even in small children up to 15 kg body weight.Blood Transfus. 2017;15:85-92. [PMID: 27136428 DOI: 10.2450/2016.0151-15]

BACKGROUND

The collection of peripheral blood stem cells, although now a routine procedure, is still a challenge in low body weight children because of specific technical and clinical issues. For paediatric patients it is crucial to obtain an adequate number of CD34+ cells with the minimum number of procedures: this can be done using large volume leukapheresis (LVL).

MATERIALS AND METHODS

We analysed the efficacy and safety of 54 autologous LVL performed in 50 children (33 [66%] males and 17 [34%] females), median age 2 years (range, 1-5) and median body weight 12 kg (range, 6-15). The procedures were performed with a COBE Spectra previously primed with red blood cells; ACD-A solution and heparin were used as anticoagulants.

RESULTS

The target CD34+ cell dose (≥5×10/kg body weight) were collected with one LVL in 46 (92%) patients, while four (8%) patients needed another procedure. All our LVL were well tolerated. Side effects were observed in five (9.2%) patients and one procedure had to be discontinued because of catheter-related haemorrhage. The platelet count decreased significantly (p<0.001) after each procedure but without bleeding or need for transfusion support.

DISCUSSION

Our experience confirms that LVL is efficient and safe even in small children, if the procedure is adjusted considering the weight and age of child. The most important factors are good venous access, adequate preparation of the child's electrolyte status, and surroundings in which the small child as well as parents feel comfortable, and can tolerate the procedure better. Although a median platelet loss of 50% can be expected, LVL is safe and reduces the overall number of procedures required. It can be recommended for peripheral blood stem cell collection even in small body weight children with malignant diseases, particularly those who mobilise low numbers of CD34+ cells.

Peripheral blood stem cell collection in children: Management, techniques and safety

Peripheral blood stem cell (PBSC) collection as a source of haematopoietic stem cells is steadily increasing. The collection procedure in children is more difficult than in adults because of the low blood volume and the poor venous access. Special apheresis equipment has been developed for paediatric PBSC collections to reduce the extracorporeal volume thereby avoiding circulatory side effects. Priming of the disposable with red blood cells and/or human albumin is recommended for children weighing less than 30kg. Poor venous access usually requires a special paediatric catheter to allow for a blood flow that results in the formation of a cell layer for the collection of PBSC. An optimal time point with a maximum peak of CD34+ cells should be chosen for the harvesting of PBSC to reduce the duration of the apheresis and possible side effects.

Progenitor cell recruitment during individualized high-flow, very-large-volume apheresis for autologous transplantation improves collection efficiency

BACKGROUND

Individual adaptation of processed patient's blood volume (PBV) should reduce number and/or duration of autologous peripheral blood progenitor cell (PBPC) collections.

STUDY DESIGN AND METHODS

The durations of leukapheresis procedures were adapted by means of an interim analysis of harvested CD34+ cells to obtain the intended yield of CD34+ within as few and/or short as possible leukapheresis procedures. Absolute efficiency (AE; CD34+/kg body weight) and relative efficiency (RE; total CD34+ yield of single apheresis/total number of preapheresis CD34+) were calculated, assuming an intraapheresis recruitment if RE was greater than 1, and a yield prediction models for adults was generated.

RESULTS

A total of 196 adults required a total of 266 PBPC collections. The median AE was 7.99 x 10(6), and the median RE was 1.76. The prediction model for AE showed a satisfactory predictive value for preapheresis CD34+ only. The prediction model for RE also showed a low predictive value (R2 = 0.36). Twenty-eight children underwent 44 PBPC collections. The median AE was 12.13 x 10(6), and the median RE was 1.62. Major complications comprised bleeding episodes related to central venous catheters (n = 4) and severe thrombocytopenia of less than 10 x 10(9) per L (n = 16).

CONCLUSION

A CD34+ interim analysis is a suitable tool for individual adaptation of the duration of leukapheresis. During leukapheresis, a substantial recruitment of CD34+ was observed, resulting in a RE of greater than 1 in more than 75 percent of patients. The upper limit of processed PBV showing an intraapheresis CD34+ recruitment is higher than in a standard large-volume leukapheresis. Therefore, a reduction of individually needed PBPC collections by means of a further escalation of the processed PBV seems possible.

Collection, storage, and infusion of stem cells in children with high-risk neuroblastoma: saving for a rainy day

In this position statement issued by the Hematopoietic Stem Cell Transplant Discipline and the Neuroblastoma Disease Committee of the Children's Oncology Group (COG), we address the feasibility and advisability of collecting sufficient peripheral blood stem cells in neuroblastoma patients to both support the planned initial HDC/SCR procedure(s) as well as allow for therapies, potentially utilized after a recurrence of disease, that may require PBSC support. An additional aliquot of cells for potential subsequent therapies could be collected at the time of the initial PBSC apheresis episode, by any of extending the collection time, extending the apheresis episode by a single day, or cryopreserving a separate aliquot from collections in which large numbers of CD34+ cells are collected.

Mobilizing the older patient with myeloma

Although hematopoietic progenitor/stem cells (HPC) have been used for autologous transplants for approximately 25 years, it is only recently that we have begun to finally understand the factors which play important roles in causing these cells to leave their marrow niches and circulate in the blood. Still less is understood about factors important in homing of these cells from the blood to the marrow, and their re-engraftment there. Nonetheless, a significant amount of clinical information exists on how to make these cells leave the marrow in order to facilitate their collection from the blood for use as a transplant graft. This review provides an overview of what is currently known about the factors influencing mobilization of HPC from the marrow into the blood. Further, it suggests how this knowledge may be used to individually optimize collection of HPC. It is particularly important to optimize collection in the older myeloma patient, where it has traditionally been difficult to collect adequate numbers of cells for the tandem transplant now thought to provide the best hope for long-term survival in this disease.

Mononuclear cell variability and recruitment in non-cytokine-stimulated donors after serial 10-liter leukapheresis procedures

BACKGROUND

We introduced monitoring of mononuclear cell (MNC) counts to obtain enhanced donor control and a stable quality of MNC products, because there are limited data available about blood donors after serial leukapheresis (LP) procedures.

STUDY DESIGN AND METHODS

In a prospective paired study, 13 male healthy blood donors underwent 10-L LP procedures performed on two apheresis devices by use of two MNC program settings (COBE Spectra, Gambro BCT, SF 250 vs. SF 500; and AS.TEC 204, Fresenius Hemocare, CP 129 vs. CP 194). Donors' pre- and postdonation MNC counts were analyzed by fluorescence-activated cell sorting.

RESULTS

After each 10-L LP procedure, a transient decline (p < 0.05) of CD14+ monocyte and platelet counts appeared in donors. Loss of donors' CD3+ T cells, CD19+ B cells, and CD16+56+ natural killer (NK) cells during MNC collection was partly compensated by cell recruitment. The MNC recruitment factor (RF) seems to be higher with high-yield MNC program settings. Negative correlations (p < 0.01) were noticed between predonation counts and RFs of CD3+ T cells and CD16+56+ NK cells. Four serial 10-L LP procedures did not result in long lasting MNC depletion for donors.

CONCLUSION

MNC recruitment seems to depend on MNC program settings and collected cell yields. Low MNC counts could result in high cell recruitment that may contribute to stable collection results to some degree. Nevertheless, there seems to be a considerable individual variation of MNC recruitment in donors that should be investigated in more detail.

Apheresis techniques for collection of peripheral blood progenitor cells

The combination of effective mobilisation protocols and efficient use of apheresis machines has caused peripheral blood progenitor cells (PBPC) transplantation to grow rapidly. The development of apheresis technology has improved over the years. Today PBSC procedures have changed towards systems to minimise operator interaction and to reduce the collection of undesired cells such as polymorphonuclear cells and platelets using functionally closed, sterile environments for PBSC collection in keeping with Good Manufacturing Practice guidelines. Blood cell separators with continuous flow technique allow the processing of more blood than intermittent flow devices resulting in higher PBSC yields. Large volume leukapheresis with the processing of 3-4-fold donor's/patient's blood volume can increase the number of collected progenitor cells. Therefore, intermittent flow cell separators are indicated if only single vein access is available. Anticoagulant induced hypocalcaemia is an often observed side effect in long lasting PBPC harvesting and monitoring of electrolytes should be performed especially at the end of the apheresis procedure to supplement low levels of potassium, calcium or magnesium. Refinement and improvement of collection techniques continue to add to the armamentarium of current approaches for cancer and non-malignant conditions and will enable future strategies.

Factors affecting the efficacy of peripheral blood progenitor cells collections by large-volume leukaphereses with standardized processing volumes

BACKGROUND

Peripheral blood progenitor cell (PBPC) collections should be safe and efficient. Therefore, the influence and risk factors in large-volume leukaphereses (LVL) with standardized blood volumes was investigated.

STUDY DESIGN AND METHODS

In a total of 724 autologous LVL performed at our center, either 4x or 6x the patient's blood volume (PBV) was processed. The group with processing 4x the PBV showed a median of 31 circulating CD34+ cells per microL, and the group with processing 6x the PBV had a median of 13 CD34+ cells per microL before LVL. Individual clinical factors, laboratory factors, and apheresis run variables influencing the yields of PBPCs were retrospectively analyzed. Furthermore, the changes of laboratory variables and adverse effects during LVL were investigated.

RESULTS

Multivariate analysis identified "age,""circulating CD34+ cells," and "percentage of mononuclear cells" as only factors influencing the yields of PBPCs. Altogether, processing 6x versus 4x the PBV did not result in significantly higher yields of CD34+ cells for the total group, but requested PBPC yields were achieved more often after processing 6x the PBV in patients below 20 CD34+ cells per microL blood. Processing 6x versus 4x the PBV showed a significant difference for the decrease of platelets, but not for any other laboratory variable. Adverse effects were recorded in 4.97 percent of LVL without accumulation in one group.

CONCLUSION

In particular, patients with low amounts of circulating CD34+ cells profited from enlarged LVL demonstrating higher PBPC yields but comparable rates of adverse effects.

Pediatric large-volume leukapheresis: a single institution experience with heparin versus citrate-based anticoagulant regimens

BACKGROUND

Anticoagulant-associated toxicity may exert significant effects on the safety and efficacy of large-volume leukapheresis (LVL) in children, however, few studies specifically address management of this issue.

STUDY DESIGN AND METHODS

Seventy-four consecutive LVL procedures (mean, 4 blood volumes processed) in children weighing less than or equal to 30 kg (minimum, 10.9 kg) were analyzed. The first 21 procedures were evaluated retrospectively; 11 used heparin alone (Group I) and 10 used heparin plus reduced-dose ACD-A (whole blood to anticoagulant ratio > or =20:1) (Group II). The next 53 procedures were evaluated prospectively and used full-dose ACD-A (whole blood to anticoagulant ratio < or =13:1), intravenous divalent cation prophylaxis and no heparin; 11 used calcium alone (Group III) followed by 42 with calcium plus magnesium (Group IV).

RESULTS

Seventy-four LVL (56 PBPC and 18 MNC) collections were performed in 38 subjects. One donor in Group I experienced a significant groin hematoma at the site of line placement. One donor each in Groups III and IV had mild paresthesias. Despite a mean citrate infusion rate of 2.6 mg per kg per minute, mean postapheresis serum potassium and ionized magnesium and calcium concentrations in Group IV declined by only 9, 8, and 4 percent, respectively, and stable levels of these variables were maintained 24 hours later. Postapheresis PLT counts declined significantly from baseline preapheresis levels in all groups (mean, 52% decrease).

CONCLUSIONS

Use of full-dose citrate anticoagulant with prophylactic intravenous divalent cation infusion offers an effective and safe approach to management of anticoagulant-related toxicity in children undergoing LVL.

Hematopoietic progenitor cell large volume leukapheresis (LVL) on the Fenwal Amicus blood separator

A technique for large volume leukapheresis (LVL) for hematopoietic progenitor cell (HPC) collection using the Fenwal Amicus is presented. It was compared to standard collections (STD) with regard to CD34+ cell yields and cross-cellular content. Optimal cycle volumes and machine settings were evaluated for LVL procedures. A total of 68 patients underwent 80 HPC collection procedures. Because of differences in CD34+ cell yields associated with peripheral white blood cell counts (WBC), the comparison was divided into groups of 20 with WBC < or =35 x 10(9)/L (< or =35 K) and those >35 x 10(9)/L (>35 K). Baseline CD34+ cell counts (peripheral count when patient started HPC collection) were used (median 18-23 cells/microl). Significantly more whole blood (corrected for anticoagulant) was processed with LVL (LVL 20 l vs. STD 13.5 l). For < or =35 K, median CD34+ x 10(6), WBC x 10(9), RBC ml, Plt x 10(11) yields/collection were 183, 21.2, 14, 0.8, respectively, for STD vs. 307, 22.1, 11, 1.0, respectively, for LVL. For >35 K, median CD34+ x 10(6), WBC x 10(9), RBC ml, Plt x 10(11) yields/collection were 189, 32.7, 15, 1.4, respectively, for STD vs. 69, 40.8, 21, 1.3, respectively, for LVL. We have described a method of LVL using the Amicus that, in patients with pre-procedure WBC < or =35 x 10(9)/L, collects more CD34+ cells than a standard procedure with acceptable cross-cellular content. This method is not recommended when pre-procedure WBC counts are >35 x 10(9)/L.

Analysis of factors affecting PBPC collection in low-weight children with malignant disorders

BACKGROUND

PBPC collection in children weighing </=25 kg is hampered by technical and clinical problems related to vascular access, low total blood volume, anticoagulation, side effects, and psychological impact. The aim of this study was to analyze several clinical and technical factors, other than pre-apheresis CD34(+) count, that may affect PBPC collection in these low-weight children.

METHODS

Data from 88 leukaphereses performed in 45 children were analyzed, including pre-apheresis CD34(+) cell count, COBE Spectra software (version 4.7 versus 6.0), apheresis volume [standard versus large-volume leukapheresis (LVL)] and patient's diagnosis, age, weight and sex.

RESULTS

The median number of PBPC collected was 6.68 mononuclear cells (MNC)x10(8)/kg (range 2.36-19.05) and 1.69 CD34(+) cellsx10(6)/kg (range 0.08-13.79). Multivariate analysis showed that factors independently associated with the CD34(+) cell yield per apheresis were pre-apheresis CD34(+) cell count (P<0.001), diagnosis (P=0.008) and apheresis volume (P=0.009). Recruitment of CD34(+) cells was also independently affected by the apheresis volume, being higher in the LVL group (P=0.008).

DISCUSSION

We have demonstrated that, apart from the well-known influence of the pre-apheresis CD34(+) cell count, two other factors have a major impact on the CD34(+) cell yield: patient's diagnosis and apheresis volume. In addition, taking into account that side effects were mild and tolerable, we have confirmed that LVL is a safe and effective procedure in children </=25 kg, and that AutoPBSC software could be reliably used in these patients, provided that an experienced team performs the procedure.

Influence of preapheresis clinical factors on the efficiency of CD34+ cell collection by large-volume apheresis

We evaluated 120 leukapheresis procedures (93 patients), in order to detect clinical factors that influence the efficiency of CD34+ collection using Cobe Spectra trade mark cell separators. Hematocrit was >27% and platelet count >30 000/microl in >95% of patients. Platelet transfusions were given if the postprocedure count was &<20 000/microl. Multiple regression analysis was used to analyze putative factors, and a predictive equation defined by stepwise regression modeling. The mean efficiency was 0.59 (s.d. 0.27). Sex (M>F; P=0.01), the volume processed (inversely; P=0.01) and CD34+ cell count (inversely; P=0.04) were associated with efficiency, whereas hematocrit, platelet or leukocyte count, catheter type and patient weight were not. The effect size for predictive factors was small (R(2)=0.21). Adverse events were limited to hypocalcemia. We conclude that female sex, volume processed and CD34+ cell count adversely influence the efficiency of CD34+ cell leukapheresis. However, the impact of volume and CD34+ cell count is small, and likely to be offset by the influence of these same factors on overall yield. Leukapheresis appears to be safe and efficient for autologous blood and marrow transplantation patients with hematocrit >27% and platelet count >30 000/microl.

Large volume leukapheresis in small children: safety profile and variables affecting peripheral blood progenitor cell collection

Large volume leukapheresis (LVL) has been proposed as a simplified single-apheresis approach to collect the target number of CD34(+) cells. We retrospectively analyzed results of LVL in cytokine-mobilized patients weighing less than 20 kg to evaluate adverse events and variables affecting the yield. The only major adverse event recorded was transient and reversible systolic hypotension (three episodes). All the other adverse events were mild and did not require treatment. In multivariate analysis leukocyte count (P=0.001) and younger age (P=0.009) affected the CD34(+) cell number in the peripheral blood before apheresis. The number of CD34(+) cells before the apheresis was the only variable affecting CD34(+) cell yield in multivariate analysis (P=0.0001). In all, 77% of patients achieved the target CD34(+) cell dose of 2 x 10(6)/kg in their first apheresis. Recruitment was seen in 72% of the procedures, and this was related to the total blood volume processed (P=0.0005).

Kinetic studies during peripheral blood stem cell collection show CD34+ cell recruitment intra-apheresis

A sufficient number of CD34+ cells in the peripheral blood stem cell product is important to achieve a rapid and sustained engraftment. The purpose of the present work was to study CD34+ cell kinetics during leukapheresis. Blood samples before and after leukapheresis were analysed for CD34+ cells in 205 procedures. The number of CD34+ cells after plus the number of CD34+ cells harvested was 1.5-fold greater than the number available at the beginning of the procedure, indicating recruitment of CD34+ cells during leukapheresis. In a subgroup of 66 procedures, granulocytes and platelets were measured. In contrast to CD34+ cells, these cell fractions were not recruited to the blood stream during leukapheresis. An additional nine patients were studied with serial blood measurements during leukapheresis, showing an initial decline that was followed by an increase in CD34+ cells during leukapheresis. In conclusion, CD34+ cells are recruited to the blood during the leukapheresis procedure in contrast to granulocytes and platelets.

Stem cell mobilization

Successful blood and marrow transplant (BMT), both autologous and allogeneic, requires the infusion of a sufficient number of hematopoietic progenitor/stem cells (HPCs) capable of homing to the marrow cavity and regenerating a full array of hematopoietic cell lineages in a timely fashion. At present, the most commonly used surrogate marker for HPCs is the cell surface marker CD34, identified in the clinical laboratory by flow cytometry. Clinical studies have shown that infusion of at least 2 x 10(6) CD34(+) cells/kg recipient body weight results in reliable engraftment as measured by recovery of adequate neutrophil and platelet counts approximately 14 days after transplant. Recruitment of HPCs from the marrow into the blood is termed mobilization, or, more commonly, stem cell mobilization. In Section I, Dr. Tsvee Lapidot and colleagues review the wide range of factors influencing stem cell mobilization. Our current understanding focuses on chemokines, proteolytic enzymes, adhesion molecules, cytokines and stromal cell-stem cell interactions. On the basis of this understanding, new approaches to mobilization have been designed and are now starting to undergo clinical testing. In Section II, Dr. Michele Cottler-Fox describes factors predicting the ability to mobilize the older patient with myeloma. In addition, clinical approaches to improving collection by individualizing the timing of apheresis and adjusting the volume of blood processed to achieve a desired product are discussed. Key to this process is the daily enumeration of blood CD34(+) cells. Newer methods of enumerating and mobilizing autologous blood HPCs are discussed. In Section III, Dr. John DiPersio and colleagues provide data on clinical results of mobilizing allogeneic donors with G-CSF, GM-CSF and the combination of both as relates to the number and type of cells collected by apheresis. Newer methods of stem cell mobilization as well as the relationship of graft composition on immune reconstitution and GVHD are discussed.

Peripheral blood progenitor cell collection in low-weight children

Peripheral blood progenitor cells (PBPC) are substituting bone marrow as a source of stem cells for either autologous or allogeneic hematopoietic transplantation. Several papers have been published on the experience of various groups in their mobilization and transplantation in children. Some technical problems have derived from the size of the patient or donor in the pediatric setting. Thereby, there is some concern regarding leukapheresis in very small children (weighing less than 15-20 kg). This paper summarizes our own data and that of other groups for the mobilization and collection of PBPC in the smallest children. Data from the literature show that mobilization with cytokines alone or in combination with chemotherapy is well tolerated by these patients. Pediatric donors may be used for allogeneic transplantation with no higher incidence of complications. PBPC collection even in the smallest children is a safe and efficient procedure when performed by experienced apheresis teams.

Recruitment of CD34+ cells during large-volume leukapheresis

Mobilized peripheral blood stem and progenitor cells (PBPCs) are increasingly used to restore hematopoiesis after myeloablative treatment. To obtain a sufficient number of CD34(+) cells, many studies have focused on the improvement of the collection technique during the leukapheresis procedure (LP), and so-called large-volume leukapheresis (LVL) procedures have been developed. Such procedures can be performed by extending the duration of the LP and/or by increasing the inlet flow rate. However, no previous studies have compared the efficiency of these procedures. In the present study, we compared the kinetics of PBPCs recruitment (including CD34(+) cell subsets), the PBPCs yield, and the collection efficiency as well as the overall feasibility of the procedures during a single LVL performed by standard (group I) (median 85 ml/min; range 50-97 ml/min) and high inlet flow rates (group II) (median 130 ml/min; range 110-150 ml/min). Seven patients with hematological malignancies were enrolled and allocated to each group. The patients' blood volumes (BV) were processed four times. The apheresis product (AP) was collected in four separate bags, which were changed every time one BV had been processed. The CD34(+) cell number and CD34(+) cell subsets were assessed in the four collection bags and in peripheral blood (PB) before every time one BV had been processed and after the leukapheresis. The CD34(+) cell yield exceeded the pre-apheresis CD34(+) cell number per ml BV in 6 out of 7 patients in group I and in 3 out of 7 patients in group II. In group II, the recruitment of CD34(+) cells from the bone marrow (BM) to PB starts in the second collection period--as early as 30-60 min after initiating the procedure. No exhaustion in the recruitment was observed in the two groups for at least 5 h during the leukapheresis, and all CD34(+) cell subsets were recruited at a steady rate. However, the collection efficiency in group II was only half of that in group I. In addition, we experienced many technical problems during the leukapheresis in group II. Thus, in 4 out of 7 patients in this group, it was not possible to perform the maximal inlet flow rate because of catheter problems. In conclusion, due to the technical problems associated with the high inlet flow rate procedure and the fact that the relative number of CD34(+) cells harvested and recruited during the leukapheresis was higher in group I than II and, also reflected an approximately two-fold higher collection efficiency, we recommend that LVL be performed by standard inlet flow rate.

Trafficking of CD34+ cells into the peripheral circulation during collection of peripheral blood stem cells by apheresis

The number of CD34+ cells collected during apheresis is related to the volume of blood processed. In large-volume apheresis (LVL) procedure, more cells can be collected than were originally present in the peripheral blood at the start of the collection procedure. We prospectively studied the levels of CD34+ cells in the blood and apheresis product during LVL procedures for 21 patients with acute myelogenous leukemia or multiple myeloma. These patients experienced a slow decline in blood CD34+ cell concentrations during the apheresis procedure. No patient demonstrated a sustained rise in CD34+ cell counts as a result of the procedure. The number of CD34+ cells collected exceeded the number calculated to be in the peripheral blood at the start of the procedure by an average of 3.0-fold. The efficiency of collection for CD34+ cells averaged 92.6% and did not vary with speed of blood processing, diagnosis, or mobilization regimen. The calculated release of CD34+ cells from other reservoirs into the peripheral blood averaged 3.71 x 10(6)/min (range, 0.36-13.7 x 10(6)/min), and correlated (r = 0.82) with the concentration of these cells in the peripheral blood at the start of the procedure. These data show that the apheresis procedure used in this study does not affect the release of CD34+ cells in a cytokine-treated patient. LVL will result in collection of larger quantities of CD34+ cells than procedures involving processing of smaller volumes of blood, but the number of cells collected is limited by the rate of release of these cells into the peripheral circulation where they are accessible for collection.

Kinetics of standardized large volume leukapheresis (LVL) in patients do not show a recruitment phenomenon of peripheral blood progenitor cells (PBPC)

Although several studies have demonstrated the efficacy of large volume leukapheresis (LVL) to yield high numbers of peripheral blood progenitor cells (PBPC), the mechanisms of stem cell release into circulation and the postulated phenomenon of PBPC recruitment during apheresis have not been investigated in detail. Therefore, we analyzed the kinetics of stem cell enrichment in a total of 34 standardized LVL for patients with hematologic malignancies (lymphoma, multiple myeloma) and solid tumors (breast cancer, rhabdomyosarcoma). LVL was started 2 h after administration of G-CSF processing six times the patient's blood volume. Cells were sequentially collected into six bags and the numbers of leukocytes, mononuclear cells (MNC), CD34+ cells and colony-forming cells (CFU-GM) in each collection bag were analyzed. The numbers of PBPC collected demonstrated a continuous decrease starting after an early maximum during the second processed blood volume (P = 0.001). Interestingly, these kinetics of decreasing stem cell yields during LVL were similar for both entities of patients with hematologic malignancies as well as for both groups of patients with solid tumors. In summary, a recruitment phenomenon, defined as a time-dependent and LVL-induced increase of PBPC, could not be demonstrated in any of the diseases investigated.

Kinetics of peripheral blood stem cell collection in large-volume leukapheresis for pediatric patients undergoing chemotherapy and adult patients before chemotherapy

The present study investigated the kinetics involved in collection CD34+ cells and colony-forming units-granulocyte-macrophages (CFU-GMs) during large-volume leukapheresis (LVL) in pediatric patients with malignancies and attempted to correlate the number of cells with the processed blood volume. In addition, adult cases were also examined using the same continuous flow blood cell separator to investigate the difference between children and adults. We examined 5 pediatric patients who had undergone chemotherapy before apheresis and 3 adult patients who were scheduled to undergo chemotherapy following apheresis. Collection was performed using a continuous-flow blood cell separator. Patients received granulocyte-colony-stimulating factor (G-CSF) to mobilize peripheral blood stem cells (PBSCs), except in the case of acute myelocytic leukemia. The processed blood volume was set to approximately 300 ml in children and 500 ml/kg of body weight in adults and the leukapheresis component was collected when approximately 50 ml of blood was processed. Six sequential samples were taken from each component in pediatric patients and 10 sequential samples from adults to obtain CD34+ cells and CFU-GMs. Counts of mononuclear cells (MNCs) and CD34+ cells in peripheral blood were measured just before and after each apheresis. Hemoglobin, hematocrit, and platelet counts in peripheral blood were monitored during apheresis. A total of 11 collections were performed for pediatric patients. The mean total CD34+ cells and CFU-GMs in each fractionated yield did not show a remarkable increase with increasing volume of blood processed. In adults, the kinetics of CD34+ cells in each fractionated yield were determined on a continuous basis and CFU-GMs increased during the course of apheresis. In pediatric patients, circulating MNCs and CD34+ cells were stable during apheresis, whereas in adult patients these cells decreased in the peripheral blood after apheresis. In both pediatric and adult patients, the platelet count in the peripheral blood decreased after apheresis. In contrast to adults, in pediatric patients who had been undergone chemotherapy, the collection efficiency did not appear to increase with increased volume of blood processed. Moreover, there was a marked platelet reduction in peripheral blood following apheresis. We conclude that the kinetics of collecting PBSCs by continuous flow blood cell separator is different between pediatric cases and adults cases. The application of LVL may be prudent in some children with malignancies, including those with a low platelet count and low body weight.

Tandem high-dose therapy in rapid sequence for children with high-risk neuroblastoma

PURPOSE

Advances in chemotherapy and supportive care have slowly improved survival rates for patients with high-risk neuroblastoma. The focus of many of these chemotherapeutic advances has been dose intensification. In this phase II trial involving children with advanced neuroblastoma, we used a program of induction chemotherapy followed by tandem high-dose, myeloablative treatments (high-dose therapy) with stem-cell rescue (HDT/SCR) in rapid sequence.

PATIENTS AND METHODS

Patients underwent induction chemotherapy during which peripheral-blood stem and progenitor cells were collected and local control measures undertaken. Patients then received tandem courses of HDT/SCR, 4 to 6 weeks apart. Thirty-nine patients (age 1 to 12 years) were assessable, and 70 cycles of HDT/SCR were completed.

RESULTS

Pheresis was possible in the case of all patients, despite their young ages, with an average of 7.2 x 10(6) CD34(+) cells/kg available to support each cycle. Engraftment was rapid; median time to neutrophil engraftment was 11 days. Four patients who completed the first HDT course did not complete the second, and there were three deaths due to toxicity. With a median follow-up of 22 months (from diagnosis), 26 of 39 patients remained event-free. The 3-year event-free survival rate for these patients was 58%.

CONCLUSION

A tandem HDT/SCR regimen for high-risk neuroblastoma is a feasible treatment strategy for children and may improve disease-free survival.

A randomized trial of leukapheresis volumes, 7 L versus 10 L: an assessment of efficacy and patient tolerance

High-dose chemotherapy followed by autologous PBSC transplantation (PBSCT) has become an accepted form of therapy for a number of malignant hematologic diseases. The optimal method for the collection of PBSC is yet to be defined. Large-volume leukapheresis may be able to collect adequate numbers of PBSC with the patient undergoing fewer procedures. We routinely process 7 L of blood per leukapheresis. Hence, we elected to assess whether a modest increase in the blood volume processed would, on average, decrease the number of leukaphereses each patient needed to undergo to collect > or =2 x 10(6) CD34+ cells/kg body weight. Sixty patients were randomized to undergo 7 L leukaphereses (n = 31 patients; 87 leukaphereses) or 10 L leukaphereses (n = 29 patients; 81 leukaphereses). The median number of leukaphereses required per patient to collect the target number of CD34+ cells was two (range one to five) for both groups (p = 0.83). The median number of nucleated cells collected per patient was greater for the 10 L group (8.2 x 10(8)/kg versus 5.3 x 10(8)/kg, p = 0.005), as was the median number of mononuclear cells (MNC) (4.7 x 10(8)/kg versus 3.6 x 10(8)/kg, p = 0.0001), whereas there was no statistical difference between the groups for the median number of CD34+ cells collected per patient (3.2 x 10(6)/kg versus 3.7 x 10(6)/kg, p = 0.98). Therefore, over the 18-month period of this trial, the use of a 10 L leukapheresis volume did not decrease the number of leukaphereses performed compared with a 7 L leukapheresis volume.

Enhanced HPC recruitment in children using LVL and a new automated apheresis system

BACKGROUND

A new automated apheresis system has recently been reported as useful in improving peripheral blood HPC collection in adults. The aim of this study has been to verify the utility of this system (AutoPBSC, COBE BCT) for standard leukapheresis and for LVL in the pediatric setting.

STUDY DESIGN AND METHODS

A prospective study was set up in 29 leukapheresis procedures carried out in 26 children with malignant diseases and body weight under 40 kg who had undergone mobilization with G-CSF or with G-CSF and chemotherapy. Leukapheresis procedures were performed under two protocols, depending on the total blood volume processed: standard leukapheresis (< or=3) and LVL (>3). The need to prime the tubing set with blood was determined, and the inlet flow rate, collection time, recruitment of CD34+ cells, CD34+ cell collection efficiency, component volume, leukapheresis cell composition, and preapheresis and postapheresis peripheral blood counts were measured. Paired t test, Spearman's correlation coefficient, and the Mann-Whitney U test were employed for statistical analysis.

RESULTS

Because of the low extracorporeal volume (167 mL) of the tubing set of the automated blood processor, priming was necessary in only 2 of 26 patients, both weighing under 10 kg. LVL showed better CD34+ cell yield (7.5 vs. 2.3 x 10(6)/kg; p = 0.047), higher recruitment (2.1 vs. 0.9; p = 0.002), and greater collection efficiency (50% vs. 33%; p = 0.005) than standard leukapheresis. No significant differences were found between groups in collection time. In LVL procedures, CD34+ cell collection efficiency and recruitment were not significantly influenced by the inlet flow rate.

CONCLUSION

The AutoPBSC is a reliable system for peripheral blood HPC collection in children mainly when used in combination with LVL. The major advantage of this software is a reduced need for priming. LVL allows better CD34+ cell collection efficiency, enhanced recruitment, and improved CD34+ cell yield.

Volume-dependent collection of peripheral blood progenitor cells during large-volume leukapheresis for patients with solid tumours and haematological malignancies

We investigated the efficacy of peripheral blood progenitor cell (PBPC) collection during large-volume leukapheresis (LVL) in patients with solid tumours and haematological malignancies (n = 18). The time- and volume-dependent harvest of leucocytes (WBC), mononuclear cells (MNC), CD34+ cells and colony-forming cells (CFU-GM) during LVL was analysed in six sequentially filled collection bags processing four times the patient's blood volumes. The amounts of leucocytes (WBC) and the purity of mononuclear cells (MNC%) did not show any significant changes during LVL. The percentage of CD34+ cells remained constant for the first three bags but consecutively decreased from initially 1.71% CD34+ cells in the beginning of LVL to finally 1.34% CD34+ cells (P = 0.02). The mean numbers of colony-forming cells (CFU-GM) decreased from 74 microL-1 to 59 microL-1 during LVL (P = 0.16). Furthermore, the comparison of volume-dependent PBPC collection for patients with high, medium and low total yields of CD34+ cells showed similar kinetics on different levels for the three groups. We concluded that - relative to the initial total amount of PBPC harvested - comparable numbers of progenitor cells can be collected during all stages of LVL with a slight decreasing trend processing four times the patient's blood volumes.

A prospective, randomized, sequential, crossover trial of large-volume versus normal-volume leukapheresis procedures: effect on progenitor cells and engraftment

BACKGROUND

The influence of leukapheresis size on the number of harvested peripheral blood progenitor cells is still unclear. A prospective randomized crossover trial was thus performed, to evaluate the effect of large-volume leukapheresis (LVL) versus normal-volume leukapheresis (NVL) on progenitor cells and engraftment in 26 patients with breast cancer and 15 patients with non-Hodgkin's lymphoma who were eligible for peripheral blood progenitor cell transplantation.

STUDY DESIGN AND METHODS

Patients were randomly assigned to undergo either LVL on Day 1 and on Day 2 or vice versa. The number of progenitor cells was evaluated in the harvest and before and after leukapheresis in the peripheral blood.

RESULTS

The number of harvested CD34+ cells (4.8 x 10(6) vs. 3.4 x 10(6)/kg body weight, p < 0.001) and colony-forming units-granulocyte-macrophage (3.1 x 10(5) vs. 2.4 x 10(5)/kg body weight, p = 0.0026) was significantly higher for LVL procedures than for NVL procedures. The median extraction efficacy, defined as the difference between the yield in the harvest and the decrease in the total number of CD34+ cells in peripheral blood during leukapheresis, was significantly (p < 0.0001) higher for LVL than for NVL (2.6 x 10(8) and 8 x 10(7), respectively). In patients with breast cancer, the median amount of CD34+ cells in the harvest and the median extraction efficacy were higher for LVL than for NVL (p < 0.0001). This was not found for patients with non-Hodgkin's lymphoma.

CONCLUSION

LVL results in a higher yield of CD34+ cells and colony-forming units-granulocyte-macrophage than NVL, but only in patients with breast cancer and with high numbers of CD34+ cells in the peripheral blood before leukapheresis.

Therapeutic plasma exchange and cytapheresis in pediatric patients

Pediatric therapeutic apheresis is reviewed including what it is, how it is performed and indications for its use. Pediatric patients are special, and the unique needs for replacement fluids and attention to access, anticoagulation, volume shifts and hypothermia are stressed. While all indications cannot be addressed, the procedures most commonly performed are reviewed. These include erythrocytapheresis, leukaphereses and plasma exchanges. A table details the strength of evidence supporting the use of apheresis procedures for many of these indications.

Kinetics of peripheral blood stem cell harvests during a single apheresis

BACKGROUND

The enumeration of CD34+ cells in the peripheral blood of patients before leukapheresis is commonly used to predict the outcome of stem cell harvests. The concept that an increased number of transplanted cells gives faster marrow reconstitution triggers an interest in investigating the kinetics of peripheral blood stem cells during leukapheresis. The aim of this study was to investigate the issue of recruitment of hematopoietic progenitor cells during a single leukapheresis.

STUDY DESIGN AND METHODS

Nine leukapheresis procedures (in 8 patients) were investigated. In each case, 3 blood volumes were processed. Samples from peripheral blood, the collection line of apheresis equipment, and the collected component were obtained after each blood volume was processed. The enumeration of CD34+ cells was performed, and the total number of progenitors, as a sum of the number of cells in the peripheral blood and the number of cells in the collected component, was calculated.

RESULTS

A mean of 13.3 L of blood was processed, and a component with a mean volume of 424 mL and a mean of 10.1 x 10(6) CD34+ cells per kg of body weight was collected. White cell and mononuclear cell counts in peripheral blood declined concomitantly during the procedures. The calculated total number of cells--that is, the sum of the number of cells in the collected component and the number of cells in the peripheral blood--showed a concomitant, but not equal, rise in polymorphonuclear cells, mononuclear cells, and CD34+ cells during the leukapheresis. This apparent mobilization of progenitors into the peripheral blood did not correlate with the slightly increased number of polymorphonuclear cells or with the more pronounced increase in mononuclear cells.

CONCLUSION

There is a substantial recruitment of progenitor cells during a single leukapheresis.

Factors affecting the efficiency of collection of CD34-positive peripheral blood cells by a blood cell separator

BACKGROUND

The yield of CD34-positive cells obtained from an apheresis procedure is determined, in part, by the efficiency of collection. Optimization of the efficiency of CD34-positive peripheral blood cell collection requires identification of predictive factors.

STUDY DESIGN AND METHODS

Demographic, stem cell collection, mobilization, and disease-related measures from autologous and allogeneic donors undergoing 252 progenitor cell apheresis procedures were retrospectively reviewed. Statistical relationships between CD34 collection efficiency and the various measures were determined by correlation and multiple linear regression analysis.

RESULTS

CD34 collection efficiency inversely correlated with the peripheral white cell count, hematocrit, and serum albumin concentration (R2 = 0.29). White cell count was the single best predictor of CD34 efficiency (R2 = 0.19). Donor groups with cytopenias (patients vs. normal donors; increased cycles of prior chemotherapy; bone marrow involvement; chemotherapy plus growth factor mobilization) had higher collection efficiencies. Only 29 percent of the variability in the data could be attributed to white cell count, hematocrit, and albumin concentration. The majority of the remaining variability was due to unexplained differences between donors.

CONCLUSION

CD34 collection efficiencies show considerable variation. Higher peripheral white cell counts, hematocrits, and/or albumin concentrations result in decreased CD34 collection efficiency, but most of the variability in the data is not accounted for by these three factors.

Intra-apheresis recruitment of blood progenitor cells in children

BACKGROUND

Determination of the optimal duration of apheresis requires a careful examination of blood progenitor cell (BPC) kinetics during apheresis. Intra-apheresis recruitment of BPCs should be evaluated.

STUDY DESIGN AND METHODS

Twenty-six apheresis procedures were performed in 13 children with various malignant disorders (ages, 10 months to 17 years; median, 7 years) to collect BPCs for autologous transplant, using a blood cell separator with 2 to 5.2 blood volumes processed. The subjects were divided into three groups according to age: below 1 year (n = 4), 2 to 10 years (n = 5), and 11 to 20 years (n = 4). BPCs were mobilized by a combination of chemotherapy and granulocyte-colony-stimulating factor (G-CSF; 2-7.5 micrograms/kg/day intravenous drip). The levels of circulating CD34+ cells and colony-forming units-granulocyte-macrophage (CFU-GM) were monitored to examine intra-apheresis recruitment. For every 50 mL per kg or 2 L of processed blood, 5-mL blood samples were collected via a central line.

RESULTS

In the first apheresis procedure, more CD34+ cells were mobilized by the procedure itself in the infant group than in the older groups, and the number of cells decreased with the subject's age. When the same analysis was made during the second apheresis procedure, performed 1 day later, the levels of both CD34+ cells and CFU-GM had decreased to below the preapheresis values in all of the populations. Cell yields in the second apheresis procedure were significantly lower than those in the first.

CONCLUSION

Although several factors prevent a reliable analysis, the data suggest that the intra-apheresis recruitment of BPCs may be age-specific; the continuous and prolonged supply of cells from the bone marrow to peripheral blood that occurs during apheresis is more predominant in infants, which leads to the collection of proportionately more BPCs in younger children than in their older counterparts.