Hematopoietic Stem Cell Transplantation in Severe Pediatric Sickle Cell Disease: Outcome and long-term complications, Saudi experience at King Faisal Specialist Hospital, Riyadh, Saudi Arabia.

Background: Hematopoietic stem transplantation (HSCT) from matched related donors (MRD) is offered as a curative therapeutic option in children with Sickle cell disease (SCD).

Objective: We wanted to assess the outcome and long-term complications observed in children undergoing HSCT at a single transplant center in Saudi Arabia.

Patients and methods: One hundred and twenty-nine children were transplanted for severe Sickle cell disease (SCD) consecutively from 2006 to 2020 at our center. The main transplant indication was cerebral vasculopathy in 57 (43%), followed by the recurrent vaso-occlusive crisis (VOC) in 47 (36%). Median age at transplant was 9.1 years (range, 1.5-13.9 years). All patients received myeloablative conditioning with Busulfan, Cyclophosphamide, and Anti T-Lymphocyte Globulin (Grafalon®): BU/CY/ATG in 114 (88.4%), BU/CY in 13 (10%) and other in 2 (2%). Bone marrow was the main stem cell source in 123 (95%).

Results: All patients showed granulocyte engraftment. Acute graft-versus-host-disease (aGVHD) and chronic GVHD were observed in 26 (20%) and 12 (9%) patients, respectively. At a median follow-up of 4.36 years (range, 0.13-15.5 years), 10-year overall survival (OS) and event-free survival (EFS) of 94% and 91% was observed. The OS and EFS were significantly better in patients receiving BU/CY/ATG when compared to BU/CY (OS: 97.4%±1.5%, vs. 76.2%±12.1 P=0.003 and EFS: 94.7%±2.1% vs. 76.2%±12.1%, P=0.019).

Conclusion: HSCT for children with sickle cell disease from fully matched siblings offers the best outcome using myeloablative conditioning. However, significant toxicities were observed secondary to myeloablative regimens, in particular long-term complications, which demands exploring the use of less toxic regimens.