Single-center results reporting improved hematopoietic stem cell mobilization success in pediatric and young adult patients with solid tumors and lymphoma

Effective peripheral blood stem cell collection in a 4.6-kg child

BACKGROUND

Due to unique technical challenges, effective peripheral blood stem cell collections (PBSCs) have not been consistently reported in patients weighing less than 5 kg. We describe three PBSCs performed in a 4.6-kg child undergoing myeloablative chemotherapy for high-grade glioma.

STUDY DESIGN AND METHODS

A multidisciplinary group representing the clinical and apheresis teams adapted a PBSC protocol to accommodate the patient's size and collection targets. Special considerations included timing of the collection relative to chemotherapy, vascular access, strategies for monitoring adverse events during collection, and contingencies.

RESULTS AND DISCUSSION

The patient underwent three PBSC procedures over 2 days due to suboptimal collection after the first two procedures. For procedure 1, a conservative inlet: anticoagulant (AC) ratio and AC infusion rate of 15 and 0.6 mL/min/L total blood volume (TBV) resulted in premature discontinuation due to clotting. A ratio of 8 and AC infusion rate of 1.5-1.7 mL/min/L TBV with subsequent titration to higher levels were adopted for the second and third procedures. These changes resulted in greater acid-citrate-dextrose exposure, that was managed by continuous calcium chloride infusion. There was no hypocalcemia, hypotension, or distress during any procedure. A total of 15 × 106 CD34+ cells/kg were collected. This retrospective review illustrates that PBSC can be safely undertaken in children weighing less than 5 kg.

Dexmedetomidine for sedation during hematopoietic stem cell harvest apheresis and leukapheresis in the PICU: Guideline development

BACKGROUND

Hematopoietic stem cell (HSC) harvest apheresis and leukapheresis are performed in the pediatric intensive care unit (PICU) for high-risk pediatric patients who require procedural sedation. Patients need central access either with their own central lines, ports or require apheresis catheter (CVL) placement. Previously, patients were either awake or emerging from sedation on PICU admission. Uncertainty regarding procedural sedation plans caused delays initiating sedation and apheresis. A guideline was developed to standardize Dexmedetomidine (DEX) for procedural sedation. We investigated if guideline implementation would improve efficiency during PICU admission as demonstrated by shorter time intervals for initiation of sedation, apheresis, PICU length of stay and less alternative sedating medication.

METHODS

Data was collected retrospectively from electronic health records of preguideline and post-guideline patients who were admitted to the PICU for sedated apheresis. We compared demographic and clinical characteristics, time intervals for sedation, apheresis, PICU length of stay, and sedation agents between the two groups using Fisher Exact tests and Mann-Whitney tests, as appropriate.

RESULTS

The groups did not differ in age or weight at the time of apheresis. All intervals of time compared were shorter post-guideline. Time intervals from admission to start of sedation, admission to start of apheresis, and admission to end of apheresis were statistically significantly different. The type and number of alternative sedating medications administered did not differ between the two groups.

CONCLUSION

This guideline implementation improved efficiency during PICU admission. This study might have been too small to demonstrate statistically significant differences in other time intervals studied.

Analysis of stem cell collections in adult patients with Ewing sarcoma

BACKGROUND

Ewing sarcoma is one of the most frequent soft-tissue tumors in pediatric patients. The current treatment protocols recommend stem cell apheresis (SCA) after completion of the second course of induction therapy with vincristine, ifosfamide, doxorubicine, and etoposide (VIDE). The feasibility of SCA and graft compositions in adult patients with Ewing sarcoma have not been previously analyzed.

METHODS AND MATERIALS

The authors analyzed 29 stem cell collections of 19 adult patients (9 male, 10 female) at a median age of 27 (range 19-53) years mobilized after VIDE (n = 17), cyclophosphamide/topotecan (n = 1) or vincristine, dactinomycin and ifosfamide (n = 1) chemotherapy. All patients were mobilized with filgrastim 5 μg/kg twice daily from day +7 of chemotherapy. The collections were performed if CD34+ cell count in peripheral blood was >10/μL. The target yields were ≥4×10⁶ CD34+ cells/kg body weight.

RESULTS

Median CD34+ cells/μL in peripheral blood before SCA were 45.8 (range 6.7-614.4)/μL. The median cumulative yields were 10.6 (range 1.5-38.8) CD34+ cells/kg body weight and ≥2×10⁶ in all but two patients (89%). CD34, CD3, and CD56 yields in collections after the third VIDE and after later courses did not differ. Four patients underwent high-dose therapy with autologous transplantation, and all were engrafted.

DISCUSSION

Stem cell mobilization is feasible in most Ewing sarcoma patients. Additionally, the present study's data suggest that it is safe to postpone stem cell collection to a later VIDE chemotherapy cycle if medically indicated.