Are PBSCs a viable source for haplo-HSCT in SCD?

A study suggested that peripheral blood stem cells (PBSCs) may be the preferred option over bone marrow (BM) as a stem cell source in patients with sickle cell disease (SCD) undergoing haploidentical haematopoietic stem cell transplantation (HSCT). According to the authors, this finding could be explained by the recently improved lymphodepleting conditioning regimens.

“Recently, antithymocyte globulin (ATG) and post-transplant cyclophosphamide (PTCy) have been added to the lymphodepleting conditioning regimen of patients with SCD undergoing haploidentical HSCT [1],” explained Dr Maud Zwolsman (Amsterdam University Medical Centre, the Netherlands). “We therefore wondered whether the perceived higher risk for graft-versus-host disease (GvHD) with PBSCs is still valid.” The current retrospective study hypothesised that the use of PBSCs instead of BM would improve event-free survival, without increasing the risk of GvHD. In total, 26 patients underwent haploidentical HSCT with BM as a source, and 15 patients underwent this procedure with PBSCs [2]. “The follow-up time was significantly shorter in the PBSC group than in the BM group (259 vs 800 days; P<0.001),” mentioned Dr Zwolsman.

In the BM group, 4 events had occurred, being 3 deaths and 1 secondary graft failure, whereas no events had occurred in the PBSC group (P=0.20). Next, the 1-year incidence of grade 3-4 acute GvHD was 0% in both arms and the incidence of grade 2 acute GvHD was 23% in the BM arm and 20% in the PBSC arm (P>0.9). Moderate-to-severe chronic GvHD was observed in 1 patient in each group. “Patients in the PBSC group appeared to perform better with regard to chimerism and neutrophil engraftment,” added Dr Zwolsman.

“PBSC may have the potential to improve event-free survival as compared to BM in patients with SCD undergoing haploidentical HSCT, without increasing the risk for GvHD,” concluded Dr Zwolsman. “PBSCs are also less invasive, and do not come with the risk of ‘rescue’ stem cell harvest.” However, there was an important difference in follow-up duration, which warrants validation in a longer observation period

1. Kassim AA, et al. NEJM Evid. 2025;4(3)
2. Zwolsman M. Outcomes of peripheral blood stem cells versus bone marrow in SCD patients undergoing haploidentical HSCT. S285, EHA2025 Congress, 12–15 June, Milan, Italy.

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Posted on 2 September 20252 September 2025