Hematopoietic stem cell transplantation (HSCT) was linked to a significant reduction in vaso-occlusive events (VOEs) requiring medical care in patients with sickle cell disease (SCD), according to results of a study reported in Blood Advances.

“This study reports 2 novel findings: a higher percent myeloid chimerism in the first year after HSCT is protective against pain events, and there is improvement in VOEs even in patients who rejected their graft,” the researchers who conducted the study wrote in their report.

The researchers set out to evaluate rates of VOEs before and after completion of allogeneic HSCT in patients with SCD. The researchers assessed electronic medical records for patients with SCD who had received allogeneic HSCT at either the National Institutes of Health or the Children’s National Hospital. They examined patients’ records for numbers of VOEs requiring medical attention in the 2 years prior to HSCT and the 2 years after HSCT.

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The study evaluated 163 patients who had undergone HSCT between 2005 and 2019. Most patients (91%) had HbSS, and HSCT was performed at an average age of 21 years (range, 7 months to 64 years). Nonmyeloablative conditioning was used with 75% of patients, and HSCT involved a matched sibling donor for 72% of patients.

Across all patients, in the 2 years prior to HSCT, the mean number of VOEs was 5.6 events (range, 0-52). Over the 2 years after HSCT, the mean number of VOEs had dropped to 0.9 events (range, 0-12; P <.001).

After HSCT, in the first 12 months after HSCT the mean number of VOEs was 0.8 events (range, 0-12), and the mean was 0.1 events (range, 0-8) in the period of 12 to 24 months after HSCT (P <.001). Among patients with engraftment, VOE risk was 75% lower during the first year after HSCT, and 99% lower in the second year after HSCT.

An analysis of 20 patients who experienced graft rejection also showed a reduction in the number of VOEs following HSCT. In the 2 years before HSCT, the mean number of VOEs in this group was 6.6 events (range, 0-24). In the first 12 months after HSCT, the mean number of VOEs was 1.1 events (range, 0-6) for this group, and it was 0.8 events (range, 0-8) for the second year after HSCT (P <.001).

“Allogeneic HSCT significantly reduces the rate of painful episodes and other VOEs in the first 2 years after HSCT; thus, the benefit of acute pain cessation in patients with SCD who undergo HSCT may balance the harm for some,” the researchers concluded in their report. They also indicated that these results could support research involving autologous HSCT gene therapy for patients with SCD.

Disclosures: Some authors have declared affiliations with or received grant support from the pharmaceutical industry. Please refer to the original study for a full list of disclosures.


Leonard A, Furstenau D, Abraham A, et al. Reduction in vaso-occlusive events following stem cell transplantation in patients with sickle cell disease. Blood Adv. 2023;7(2):227-234. doi:10.1182/bloodadvances.2022008137