Hematopoietic Stem Cell Transplantation for Sickle Cell Disease in Childhood: A Single Center Experience with 45 Patients
Authors: Dedeken Laurence , Le Phu-Quoc , Azzi Nadira , Brachet Cecile , Heijmans Catherine , Huybrechts Sophie , Devalck Christine , Malou Ngalula Mujinga , Ferster Alina 
Published: October 2019

Abstract
Abstract 3103
Despite improvement in medical management, sickle cell disease (SCD) is still associated with high risk of morbidity, chronic disability and early death. Allogeneic hematopoietic stem cell transplantation (HSCT) remains the only curative approach.
Since November 1988, 45 patients (median age: 8.3 years; range: 1.7–15.3 years) with severe SCD underwent related HSCT in our unit. Thirty-five received bone marrow transplant, 3 cord blood, 6 bone marrow and cord blood and 1 peripheral blood stem cells. Two donors result from preimplantation genetic diagnosis with HLA selection. All were HLA-identical sibling except one who had one class II mismatch. All had one or more severe manifestations: 24 patients presented more than 2 vaso-occlusive crises per year, 11 recurrent acute chest syndrome, 19 cerebral vasculopathy and 4 erythroid alloimmunisation. Conditioning regimen consisted of the standard combination of busulfan, cyclophosphamide and from November 1991 antithymocyte globulins (ATG) were added: ATG Fresenius first and from July 2000 ATG Merieux. Since 1995 all patients were treated with hydroxyurea (HU) prior to transplantation for a median duration of 2.7 years (range: 0.8–10.7 years). Acute graft versus host disease (GVHD) was observed in 11 patients (3 grade III and 2 grade IV). Ten patients were treated for CMV reactivation and 4 for EBV reactivation. Only one patient had presented a probable invasive fungal disease.
After median follow-up of 6.5 years, 10 patients had presented chronic GVHD, none was extensive. Only one required therapy beyond 2 years from transplant. Engraftment was successful in 42/45. One rejection occurred 15 months after transplantation. Since HU introduction before transplant (1995), no graft failure occurred. Important mixed chimerism is present in 2 patients (AA donor) who remain free of any sickle cell disease symptoms. Two deaths occurred: 1 unexplained death 6 years after HSCT in a child free of any treatment and 1 cerebral hemorrhage 18 days after transplant in a child with severe cerebral vasculopathy. Growth was normal after transplant. As expected, gonadal function was impaired in the majority of girls. However 3 girls had spontaneous normal puberty and one had two spontaneous pregnancies with normal outcome.
Our results are very encouraging showing excellent outcomes. Both the overall survival (OS: 95.6%) and the event-free survival (EFS: 86.7%) are comparable to the other published studies, ranging from 93 to 97%, and 82 to 86 % respectively. Since 1995, all the 33 patients engrafted successfully. Previous treatment with HU may have contributed to successful engraftment. After 5.3 years of follow-up, their OS and EFS are both at 96.9%. The difference in outcome before and after 1995 is strongly significant for EFS (58.3% vs 96.9%, p=0.003). Severe cerebral vasculopathy with its risk of CNS hemorrhage remains a true challenge.

Disclosures:
No relevant conflicts of interest to declare.