Clinical Impact of Graft Cryopreservation on Allogeneic Stem Cell Transplantation: An Italian, Registry‐Based Study on Behalf of the “Gruppo Italiano Per Il Trapianto di Midollo Osseo, Cellule Staminali Emopoietiche e Terapia Cellulare” (GITMO)

Abstract

The coronavirus disease 2019 (COVID‐19) pandemic created major challenges for allogeneic hematopoietic stem cell transplantation (allo‐HSCT). Scientific societies and authorities recommended cryopreserving grafts before starting conditioning regimens, despite limited data on the clinical impact. The Italian Group for Bone Marrow Transplantation (GITMO) conducted a registry‐based study involving 3492 patients who underwent allo‐HSCT between March 2018 and September 2021. The cryopreserved cohort (n = 976) included patients who received cryopreserved grafts during the pandemic and was compared to the historical cohort (n = 2516). Graft cryopreservation was associated with a lower day 30 incidence of neutrophil and platelet engraftment (adjusted sHR = 0.8 and 0.7, p = 0.031 and p < 0.001, respectively) and delayed hematopoietic recovery. However, primary graft failure rates at day +30 were similar in the cryo and historical cohort (4% vs. 5%, respectively; p = 0.337), also after adjustment (RR = 1.19, p = 0.518). Day 100 incidence of grade II‐IV acute GVHD was comparable between the two groups (adjusted sHR = 1.2, p = 0.194). Regarding chronic GVHD incidence, we found that it was higher in patients aged < 18 years in the cryo group (adjusted sHR = 3.9, p = 0.002), but lower in those aged 18–55 years (adjusted sHR = 0.7, p = 0.008). Cumulative incidence of relapse did not differ between historical and cryo cohort (adjusted sHR 1.0. p = 0.943), as well as non‐relapse mortality (adjusted sHR 1.1, p = 0.196) and relapse‐free survival (adjusted sHR = 1.1, p = 0.197). However, a shorter overall survival was observed in the cryopreserved group (adjusted HR = 1.2, p = 0.038). Transplant centers should carefully balance the benefits and drawbacks of cryopreservation in allo‐HSCT.