Hematopoietic stem cell transplantation (HSCT) using a matched sibling donor (MSD) for patients with sickle cell disease (SCD) is associated with a high cure rate (> 90%) (Gluckman, Blood 2017). While graft failure (GF) post MSD HSCT has been reported to be extremely low at 2.3% (Gluckman, Blood 2017) the same is not true in the setting of alternative donor transplants, where GF risks varies from as low 10% in MURD (Shenoy, Blood 2016) to as high as 27-60% using other alternative donors such as haploidentical and UCB (Kamani, BBMT 2012; Bolaños-Meade, Blood 2012). An intact but hyperactive immune system often predisposes SCD HSCT recipients to a risk of GF. Other risk factors such as prior red cell allo-sensitization, insufficient suppression of erythropoiesis pre-transplant, and inadequate chelation therapy (Walters, BBMT 2001), comorbid conditions, age, presence of anti-HLA antibodies, drug toxicities, infections, cell dose, degree of donor/recipient HLA disparity and timing of second HSCT may also contribute to the risk of GF in this population (Mallhi, BMT 2017; Stepensky, Haematologica 2009).
Whilst the focus of current research is in optimizing conditioning and immunosuppressive regimens in order to reduce risk of GF and graft versus host disease (GVHD) in SCD patients undergoing alternative donor HSCT, the clinical outcomes of SCD patients post-GF including those who proceed to 2nd HSCT have not yet been studied/characterized in detail. There are reports of disease control following GF.
Despite the global burden of disease consituted by SCD, the number of patients undertaking a HSCT is limited to a restricted number of centres worlwide due to limitations in donor availability, transplant expertise and population distribution. It is, therefore, unlikely that analysis by a registry in isolation can have sufficient numbers to identify determining factors. The STAR consortium contains the largest and most detailed dataset in the US. A collaboration with CIBMTR has not progressed due to very limited data in ist registry, whereas analysis in conjunction with EBMT provides the best opportunity to describe the outcomes of this patient population and allow in-depth analysis;
• Graft failure at any time following 1st HSCT
• Patients who have an autologous reconstitution after the first HSCT
• Patients who undergo to a second HSCT from any graft source