Large-volume leukapheresis in pediatric patients

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.

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.

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.

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.

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.