Universal Engraftment after Allogeneic Hematopoietic Cell Transplantation Using Cryopreserved CD34-Selected Grafts

Area of Science:

• Hematology
• Immunology
• Transplantation Medicine

Background:

• The COVID-19 pandemic necessitated a shift to cryopreserved grafts for allogeneic hematopoietic cell transplantation (allo-HCT).
• Concerns exist regarding potential increased nonengraftment risk with cryopreserved allografts.
• No prior studies evaluated cryopreservation of CD34-selected hematopoietic progenitor cells (CD34⁺ HPCs) as the sole graft source.

Purpose of the Study:

• To assess clinical outcomes following allo-HCT using cryopreserved CD34⁺ HPCs from unrelated donors or matched siblings.
• To evaluate the safety and efficacy of cryopreservation for CD34-selected allografts.

Main Methods:

• Single-center analysis of adult patients with hematologic malignancies undergoing allo-HCT with cryopreserved CD34⁺ HPC grafts (January 2010 - June 2017).
• Standard ablative conditioning and rabbit antithymocyte globulin prophylaxis were administered.
• CD34⁺ HPCs were selected, cryopreserved using DMSO, and stored in vapor-phase liquid nitrogen.

Main Results:

• All 64 patients achieved engraftment, with a median time of 11 days post-transplant.
• Two-year overall survival (OS) was 70% for cryopreserved grafts versus 62% for fresh grafts (P=.5).
• Two-year relapse-free survival (RFS) was 59% for cryopreserved grafts versus 56% for fresh grafts (P>.9).
• Rates of relapse, nonrelapse mortality (NRM), and acute graft-versus-host disease (GVHD) were comparable between cryopreserved and fresh grafts.

Conclusions:

• Cryopreservation of CD34⁺ HPCs is a safe procedure for allo-HCT.
• Outcomes including engraftment, GVHD, and survival are consistent with fresh allogeneic CD34⁺ HPC grafts.
• The cryopreservation method demonstrated high cell viability and recovery, supporting its clinical application.