Defining “poor mobilizer” in pediatric patients who need an autologous peripheral blood progenitor cell transplantation

Abstract

The definition of poor mobilizers is not clear in pediatric patients undergoing autologous peripheral blood hematopoietic progenitor cell (HPC) mobilization. Most studies conducted in children define those variables related to the collection of HPC after leukapheresis, but the information regarding exclusively the mobilization process is scarce. In our experience, most children (92.2%) reach the target CD34(+) cell dose for autologous peripheral blood progenitor cell transplantation if CD34(+) cell count was higher than 10/μL. No differences were observed between those with >20 CD34(+) cells/μL and 11-20 CD34(+) cells/μL. In this study, we analyzed the variables that influence CD34(+) cell count; we found that prior use of radiotherapy was the main variable related to poor mobilization. Patients diagnosed with Ewing sarcoma, treated with radiotherapy and mobilized with standard doses of granulocyte colony-stimulating factor (G-CSF) were also at a high risk of mobilization failure. In these patients, we should consider mobilization with high dose G-CSF and be prepared with new mobilization agents to avoid delay on their course of chemotherapy.

Predictive factors for successful peripheral blood stem cell mobilization and collection in children

“…A study of 179 patients undergoing PBSC apheresis showed that 92% of patients can reach their target CD34 + dose if the pre‐apheresis PB‐CD34 + count was >10. There was no difference found for those with PB‐CD34 + > 20 vs 11‐20 in the study . Similarly, in our study all successful collections occurred in patients with a PB‐CD34 + > 10; however, among the four failed collections with a PB‐CD34 + < 20, all were between 10 and 20.…”

“…Factors that predict poor mobilization include underlying disease, involvement of bone marrow by metastatic disease and relapse . Treatment related factors include multiple lines of previous therapy, in particular marrow toxic agents such as purine analogs, mid‐cycle vincristine chemotherapy given prior to apheresis, and previous exposure to radiation . Factors related to the mobilization regimen include a higher yield with chemotherapy + G‐CSF than with G‐CSF alone and total G‐CSF dose .…”

“…SCC failure can occur either upfront when patients fail to mobilize and SCC is not even attempted, or when the CD34 + stem cell yield fails to meet the target dose required for transplant(s). Overall, SCC success rates range from 41 to 87% in adult and 83 to 92% in pediatric patients …”

Plerixafor combined with standard regimens for hematopoietic stem cell mobilization in pediatric patients with solid tumors eligible for autologous transplants: two-arm phase I/II study (MOZAIC)

“…Few studies have been published exploring poor mobilization in pediatric patients and therefore there is no current consensus threshold for poor mobilization in this patient group. In a single retrospective study of pediatric patients, who received a mobilization regime consisting of G-CSF for 4 days, prior to collection of CD34+ cells, [8] no differences were observed in the numbers of patients reaching the target cell dose (2 × 10 6 cells/µL) for autologous PB progenitor cell transplantation in patients with baseline PB CD34+ cells counts of >20 cells/µL compared with those with baseline CD34+ cells counts of 11-20 cells/µL [8]. Of 26 pediatric patients with a PB CD34+ cell count of ≤10 cell/µL, 18 underwent hematopoietic progenitor cell collection, two reached the target CD34+ cell dose after one apheresis, and 16 failed to reach the target [8].…”

Regulatory Systems in Bone Marrow for Hematopoietic Stem/Progenitor Cells Mobilization and Homing

“…G-CSF has been reported to fail to mobilize a sufficient number of PBSCs for transplantation in some elderly patients and especially in patients with a history of chemotherapy or radiotherapy [69, 84, 85, 93, 97, 103]. Other factors associated with poor mobilization include a low platelet count immediately before mobilization [85], baseline thrombocytopenia [85, 92], diabetes [104], and a low TNF- α level [105].…”