Effect of Cryopreservation in Unrelated Bone Marrow and Peripheral Blood Stem Cell Transplantation in the Era of the COVID-19 Pandemic: An Update from the Japan Marrow Donor Program.

During the COVID-19 pandemic, donor grafts are frequently cryopreserved to ensure that a graft is available before starting a conditioning regimen. However, there have been conflicting reports on the effect of cryopreservation on transplantation outcomes. Also, the impact of cryopreservation may differ in bone marrow (BM) transplantation (BMT) and peripheral blood stem cell (PBSC) transplantation (PBSCT). In this retrospective study, we analyzed the clinical data of both cryopreserved unrelated BMTs (n = 235) and PBSCTs (n = 118) and compared these with data from a large control cohort without cryopreservation including 4133 BMTs and 720 PBSCTs. Among the patients with cryopreserved grafts, 10 BMT recipients (4.3%) and 3 PBSCT recipients (2.5%) did not achieve neutrophil engraftment after transplantation, including 4 of the former and all 3 of the latter who died early before engraftment. In a multivariate analysis, cryopreservation was not associated with neutrophil engraftment in BMT but significantly delayed neutrophil engraftment in PBSCT (hazard ratio [HR], .82; 95% confidence interval [CI], .69 to .97; P = .023). There was an interaction with borderline significance between cryopreservation and the stem cell source (P = .067). Platelet engraftment was delayed by cryopreservation after both BMT and PBSCT. Only 2 cryopreserved grafts (<1%) were unused during the study period. The cryopreservation of unrelated donor BM and PBSC grafts is associated with a slight delay in neutrophil and platelet engraftment but an acceptable rate of graft failure. PBSC grafts may be more sensitive to cryopreservation than BM grafts. Cryopreservation is a reasonable option during COVID-19 pandemic, provided that the apheresis and transplantation centers are adept at cryopreservation. © 2022 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

Cryopreservation of Unrelated Hematopoietic Stem Cells from a Blood and Marrow Donor Bank During the COVID-19 Pandemic: A Nationwide Survey by the Japan Marrow Donor Program.

During the COVID-19 pandemic, donor hematopoietic stem cell grafts are frequently cryopreserved to ensure the availability of graft before starting a conditioning regimen. However, the safety of cryopreservation has been controversial in unrelated hematopoietic stem cell transplantation (HSCT), especially for bone marrow (BM) grafts. In addition, in unrelated HSCT, the effect of the time from harvest to cryopreservation of donor grafts required for the transportation of donor graft has not been fully clarified. In this study, we retrospectively analyzed the first 112 patients with available data who underwent cryopreserved unrelated blood and marrow transplantation through the Japan Marrow Donor Program during the COVID-19 pandemic. There were 112 patients, including 83 who received BM grafts and 29 who received peripheral blood stem cell (PBSC) grafts. The median time from stem cell harvest to cryopreservation was 9.9 hours (range, 2.6 to 44.0 hours), and the median time from cryopreservation to infusion was 231.2 hours. The incidence of neutrophil engraftment at day 28 after HSCT was 91.1%, and among 109 patients (excluding 3 patients with early death), all but 1 patient achieved neutrophil engraftment within 60 days after HSCT. The time to neutrophil engraftment and time to platelet engraftment were shorter in PBSC transplantation compared with BM transplantation (BMT), but the differences were not statistically significant (P = .064 and .18). Multivariate analysis among BM recipients revealed that a higher number of frozen nucleated cells and the absence of HLA mismatch were associated with faster neutrophil engraftment. The time to neutrophil engraftment after unrelated cryopreserved BMT was not different from that after unrelated BMT without cryopreservation. Our findings suggest that unrelated donor BM and PBSC grafts can be safely cryopreserved even after transit from the harvest center to the transplantation center. In the current COVID-19 pandemic, cryopreservation can be considered as an option while balancing the risks and benefits of the procedure.