Allogeneic hematopoietic cell transplantation for hemophagocytic lymphohistiocytosis (HLH) disorders is associated with substantial morbidity and mortality.
The effect of conditioning regimen groups of varying intensity on outcomes after transplantation was examined to identify an optimal regimen(s) for HLH disorders.
Included are 261 patients with HLH disorders transplanted between 2005-2018. Risk factors for transplant outcomes by conditioning regimen groups were studied using Cox regression models.
Four regimen groups were studied: 1) fludarabine (Flu), melphalan (Mel), n=123; 2) Flu, Mel, thiotepa (TT) n=28, 3) Flu, busulfan (Bu), n=14; and 4) Bu, cyclophosphamide (Cy), n=96. The day-100 incidence of veno-occlusive disease (VOD) was lower with Flu/Mel (4%) and Flu/Mel/TT (0%) compared to Flu/Bu (14%) and Bu/Cy (22%), p<0.001. The 6-month incidence of viral infections was highest after Flu/Mel (72%) and Flu/Mel/TT (64%) compared to Flu/Bu (39%) and Bu/Cy (38%), p<0.001. Five-year event-free survival (alive and engrafted without additional cell product administration) was lower with Flu/Mel (44%), compared to Flu/Mel/TT (70%), Flu/Bu (79%) and Bu/Cy (61%), p=0.002. The corresponding 5-year overall survival was 68%, 75%, 86% and 64% and did not differ by conditioning regimens (p=0.19). Low event-free survival with Flu/Mel is attributed to high graft failure (42%) compared to Flu/Mel/TT (15%), Flu/Bu (7%) and Bu/Cy (18%), p<0.001.
Given the high rate of graft failure with Flu/Mel, and the high rate of VOD with Bu/Cy and Flu/Bu, Flu/Mel/TT may be preferred for HLH disorders. Prospective studies are warranted.

Copyright © 2021. Published by Elsevier Inc.