A Retrospective Analysis of Fresh versus Cryopreserved Allogenic Bone Marrow Transplant within a Pediatric Population: A Change in Practice Due to the COVID-19 Pandemic.

Background: Several adult studies show mixed reports in clinical outcomes between cryopreserved and fresh stem cell products, with majority reporting no significant differences and others report that there are differences in outcomes. There is limited literature reporting its impact on outcomes in pediatric hematopoietic cell transplantation (HSCT).

Objective: To compare clinical outcomes between fresh vs cryopreserved stem cell treatment in pediatric HSCT.

Study design: A retrospective chart review was conducted on allogenic HSCT at Phoenix Children's Hospital between January 1, 2016, and March 31, 2023. The study included 181 patients, with 105 receiving fresh stem cell products and 76 receiving cryopreserved products. Clinical outcomes including, neutrophil and platelet recovery, graft versus host disease, immune reconstitution and survival outcome were compared.

Results: Study subjects had median follow-up of 997 (range 12-2642) days. 92 patients were treated for a malignant disease (leukemia/lymphoma) and 89 were treated for a non-malignant disease (hemoglobinopathies, immunodeficiency/immune dysregulation, and bone marrow failure). 124 stem cell products were from bone marrow and 57 were from peripheral blood. Comparisons between fresh vs cryopreserved treatments found no significant difference in days to neutrophil engraftment (p=0.47) or platelet engraftment (p=0.94). No difference in the incidence of acute graft versus host disease or chronic graft versus host disease (p = 0.70) between both groups. Immune reconstitution at 365 days post-transplant did not vary significantly between treatment groups for CD4+ T cells, CD8+ T cells, CD19+ B cells, and CD56/16+ NK cells. Overall survival at 2 years was similar in the fresh vs cryopreserved (86.7% vs 84.2%; p = 0.64).

Conclusion: These observations suggest that cryopreserved stem cell product is a reasonable alternative with comparable efficacy and potentially offering logistical advantages. Further research with larger pediatric cohorts is recommended to confirm non-inferiority of cryopreserved treatments in pediatric HSCT.