ABSTRACT
The World Health Organization (WHO) declared COVID-19 a pandemic in March 2020. Since then, logistical challenges arose regarding the procurement of allogeneic (allo) hematopoietic stem cell (HSC) donor grafts. Little data was available on transplant outcomes using cryo haploidentical (haplo) HSC grafts with post-transplant cyclophosphamide (PTCy) for GVHD prophylaxis. We retrospectively analyzed patients who received a first PTCy-based haplo hematopoietic stem cell transplant (Haplo HCT) at a single outpatient transplant center between January 2015 and December 2021. We identified 294 patients, 179 received a fresh graft and 115 received a cryo graft (Table 1). Both cohorts were similar in terms of median age, diagnoses, HCT-CI score and DRI. Out of 179 fresh haplo grafts, 160 (89.4%) were from peripheral blood stem cells (PBSC) and 19 (10.6%) were bone marrow grafts (BM). There were no cryo BM grafts used. Conditioning intensity were similar amongst both cohorts, with 43% myeloablative, 41.9% non-myeloablative and 15.1% RIC regimens used for fresh Haplo HCT and 39.1% myeloablative, 42.6% non-myeloablative and 18.3% RIC cryo Haplo HCT. Median time to engraftment was 16 days for fresh Haplo HCT and 17 days for cryo HCT (p=0.18). Median time to platelet engraftment was 27 days for fresh Haplo HCT and 27.5 days for cryo HCT (p=0.96). Since March 2020, only 8 transplants performed at our institution were from fresh haplo HSC grafts. Cryo grafts performed after March 2020 accounted for 73 (63.5%) of 115 total cryo Haplo HCT performed in the period reviewed. Using a Cox model to evaluate the effect of graft type and adjusting for significant variables, we found no difference in overall survival (OS), disease free survival (DFS), non-relapse mortality (NRM) and relapse rates between fresh and cryo Haplo HCT performed (Figure 1). While we found no difference in grades III-IV aGVHD (Table Presented) (Figure Presented) between fresh vs cryo Haplo HCT, we found a statistically significant higher incidence of grades II-IV aGVHD (p=0.033). There was no difference in all-grade cGVHD (p=0.53) or moderate- severe cGVHD (p=0.86) (Figure 2).(Figure Presented) The National Marrow Donor Program (NMDP) released a statement requiring cryopreservation of unrelated donor grafts at the start of the COVID-19 pandemic. The cryopreservation of all types of allo HSC grafts has been adopted by many transplant programs including ours. Our results mimic a CIBMTR analysis published at the start of the pandemic, where survival outcomes using fresh vs cryo haplo HSC grafts with PTCy as GVHD prophylaxis were similar. Contrary to other reports, we did not see differences in graft failure or rates of cGVHD between fresh and cryo Haplo HCT. The use of cryopreserved HSC grafts for Haplo HCT with PTCy results in favorable outcomes in an outpatient transplant setting. Further studies are needed to determine the cost-effectiveness of this practice in the post-pandemic era.Copyright © 2023 American Society for Transplantation and Cellular Therapy