Reduction in vaso-occlusive events following stem cell transplantation in patients with sickle cell disease.

Hematopoietic stem cell transplantation (HSCT) is potentially curative in patients with sickle cell disease (SCD). Patients with stable donor engraftment after allogeneic HSCT are generally reported to not experience SCD-related complications; however, there are no published data specifically reporting the change in vaso-occlusive events (VOE) after HSCT. Data regarding the number of VOEs requiring medical attention in the 2 years prior to allogeneic HSCT were compared to the number of VOEs in the 2 years (0-12 months and 12-24 months) after allogeneic HSCT in patients with SCD. One-hundred sixty-three patients with SCD underwent allogeneic HSCT between 2005-2019. The average age at the time of HSCT was 21 years (range 7 months - 64 years). Most patients underwent non-myeloablative conditioning [75% (N=123)] and with a matched sibling donor [72% (N=118)]. The mean number of VOEs was reduced from 5.6 (range 0-52) in the 2 years prior to HSCT to 0.9 (range 0-12) in the 2 years post-HSCT(p<0.001). Of the post-HSCT events, VOE was more frequent during the first 12 months [0.8 (range 0-12)] compared to months 12-24 post-HSCT [0.1 (range 0-8)](p<0.001). In patients who had graft rejection (12%, N=20), VOEs were reduced from 6.6 (range 0-24) before HSCT to 1.1 (range 0-6) and 0.8 (range 0-8) in the 0-12 months and 12-24 months after HSCT, respectively (p<0.001). VOEs requiring medical care are significantly reduced after allogeneic HSCT for patients with SCD. These data should inform the results of newer autologous HSCT gene therapy approaches.