Real-World Experience of Cryopreserved Allogeneic Hematopoietic Grafts during the COVID-19 Pandemic: A Single-Center Report

Abstract

In response to the widespread COVID-19 pandemic, cryopreservation of allogeneic donor apheresis products was implemented to mitigate the challenges of donor availability and product transport. Although logistically beneficial, the impact of cryopreservation on clinical outcomes and graft composition remains unclear. In this study, we compared outcomes and graft composition with cryopreserved versus fresh allografts in the setting of allogeneic hematopoietic cell transplantation (allo-HCT). We retrospectively analyzed the clinical outcomes of 30 consecutive patients who received cryopreserved allografts between March and August 2020 and 60 consecutive patients who received fresh allografts before the COVID-19 pandemic. Primary endpoints were hematopoietic engraftment and graft failure (GF), and secondary outcomes were overall survival (OS), relapse-free survival (RFS) and nonrelapse mortality (NRM). In addition, extended immunophenotype analysis was performed on cryopreserved and prospectively collected fresh apheresis samples. Compared with recipients of fresh allografts, both neutrophil and platelet recovery were delayed in recipients of cryopreserved reduced-intensity conditioning (RIC) allo-HCT, with a median time to engraftment of 24 days versus 18 days (P = .01) for neutrophils and 27 days versus 18 days (P = .069) for platelets. We observed primary GF in 4 of 30 patients in the cryopreserved cohort (13.3%) versus only 1 of 60 patients (1.7 %) in the fresh cohort (P = .03). Cryopreserved RIC allo-HCT was associated with significantly lower median total, myeloid, and T cell donor chimerism at 1 month. OS and RFS were inferior for cryopreserved graft recipients (hazard ratio [HR], 2.16; 95% confidence interval [CI], 1.00 to 4.67) and HR, 1.90; 95% CI, 0.95 to 3.79, respectively. Using an extended immunophenotype analysis, we compared 14 samples from the cryopreserved cohort to 6 prospectively collected fresh apheresis donor samples. These analyses showed both a decrease in total cell viability and a significantly reduced absolute number of natural killer cells (CD3^-CD56⁺) in the cryopreserved apheresis samples. In this single-institution study, we found delayed engraftment and a trend toward clinical inferiority of cryopreserved allografts compared with fresh allografts. Further evaluation of the use of cryopreserved allografts and their impact on clinical and laboratory outcomes is warranted.

Keywords: Cryopreserved allografts; Engraftment failure; Graft composition; Reduced-intensity conditioning.

Figure 1

Hematopoietic recovery in recipients of cryopreserved grafts versus fresh grafts. (A) Neutrophil engraftment in RIC allo-HCT. (B) Platelet engraftment in RIC allo-HCT. (C) Neutrophil engraftment in MAC allo-HCT. (D) Platelet engraftment in MAC allo-HCT.

Figure 2

Donor chimerism in PBSCs or BM in recipients of cryopreserved versus fresh grafts as assessed by short tandem repeat analysis and immunomagnetic beads coated with monoclonal antibodies against CD3 and CD15. (A) Total, myeloid (CD15), and T cell (CD3) donor chimerism (%) at 1 month post-RIC allo-HCT. (B) Total, myeloid (CD15), and T cell (CD3) donor chimerism (%) at 3 months post MAC allo-HCT. ****P < .0001; **P < .001; ns, nonsignificant.

Figure 3

Kaplan-Meier curves for OS (A) and RFS (B) in recipients of allo-HCT with cryopreserved grafts and fresh grafts.

Figure 4

Cumulative incidence of NRM in recipients of allo-HCT with cryopreserved grafts and fresh grafts for all patients (A), patients receiving RIC regimens (B), and patients receiving MAC regimens.

Figure 5

Characteristics of the apheresis products in cryopreserved versus fresh allografts. (A) Percentage of viable cells as assessed by FACS using propidium iodide dead cell exclusion in fresh and cryopreserved grafts. (B) Absolute counts (cells/µL) of CD34⁺ cells as assessed by FACS in fresh and cryopreserved apheresis samples. (C) Absolute counts (cells/µL) of HSCs (CD34⁺CD38^-CD90⁺CD45RA^-) as assessed by FACS in fresh and cryopreserved apheresis samples. (D) Representative FACS plots in 1 fresh and 1 cryopreserved apheresis sample from allogeneic donors. Gated from lymphocytes. T cells (CD56⁻CD3⁺), NK cells (CD56⁺CD3⁻), memory T cells (CD45RO⁺CD45RA⁻), naïve T cells (CD45RO⁻CD45RA⁺). (E) Absolute counts (cells/µl) of NK, T and B (CD19⁺CD20⁺) cells as assessed by FACS in fresh as compared to cryopreserved apheresis samples. (F) Absolute counts (cells/µl) of total, memory and naïve CD4⁺ T cells as assessed by FACS in fresh as compared to cryopreserved apheresis samples. (G) Absolute counts (cells/µl) of total, memory and naïve CD8⁺ T cells as assessed by FACS in fresh as compared to cryopreserved apheresis samples.