Impact of Cryopreservation of Peripheral Blood Stem Cells (PBSC) in Transplantation from Matched Unrelated Donor (MUD)

Background: Cryopreservation of PBSC for allogenic hematopoietic stem cell transplantation (allo-HSCT) was implemented due to the current Coronavirus 2019 pandemic. The impact of match unrelated donor (MUD) graft freezing on the outcome of allo-HSCT in terms of hematological recovery, graft versus host disease (GVHD), and survival are still controversial. Methods: In this study, we compared graft composition, clinical characteristics, and outcome of 31 allo-HSCT from MUD cryopreserved PBSC (Cryo Group) with 23 matched-pair allo-HSCT from fresh MUD PBSC (Fresh Group) performed in our center between January 2020 and July 2021. Results: No significant differences were recognized in clinical characteristics of patients, donors, and transplants between the Cryo and Fresh groups except for a better prognostic comorbidity index (HCT-CI) of the Cryo group. In the Cryo Group, the median time from apheresis to cryopreservation was 46.0 h (range 23.8-53.5), while the median time from cells collection and reinfusion was 13.9 days (range 5.8-28.1). In the Fresh Group, median time from apheresis to reinfusion was 35.6 h (range 21.4-51.2). The number of viable (7-AAD negative) CD34+ cells per kg patient infused was significantly lower in the Cryo Group (5.2 +/- 1.9 x 10(6)/kg vs. 7.0 +/- 1.3 x 10(6)/kg; p < 0.001). Indeed, there was a 36% (11-70) median loss of viable CD34+/kg cells after freezing. All patients engrafted: median time to neutrophil engraftment (>0.5 x 10(9)/L) was 13.5 days (range 12-15) for Cryo Group and 14 days (range 13-16) days for Fresh Group (p = 0.522), while the median time to platelet engraftment (>20 x 10(9)/L) was, respectively, 14 (range 12-18) and 15 (range 12-17) days (p = 0.904). The incidence of grade >= 2 acute GVHD was similar in the two groups (56.5% Cryo Group vs. 60.0% Fresh Group; p = 0.832) and no differences in terms of OS (p = 0.090), PFS (p = 0.200) and TRM (p = 0.970) were observed between the Cryo and Fresh groups. Conclusions: In our series, no differences between the Cryo and Fresh groups were found in engraftment, grade >= 2 acute GVHD incidence, OS, PFS, and TRM despite a lower CD34+ infused dose in the Cryo Group. Frozen PBSCs could be considered a safe option also for allo-HSCT from MUD but a higher amount of PBSC should be collected to warrant an adequate viable CD34+ post-thawing.

Automated summary

This study compared the characteristics and outcomes of cryopreserved peripheral blood stem cell transplantation and fresh peripheral blood stem cell transplantation from matched unrelated donors. The results showed no significant differences between the two groups in terms of engraftment, acute GVHD incidence, overall survival, progression-free survival, and treatment-related mortality.