G-CSF-Primed Peripheral Blood Stem Cell Haploidentical Transplantation Could Achieve Satisfactory Clinical Outcomes for Severe Aplastic Anemia Patients.

Background: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) continues to be a cornerstone in the treatment of severe aplastic anemia (SAA). The advancement of haploidentical hematopoietic stem cell transplantation (haplo-HSCT) has broadened therapeutic possibilities, particularly for patients lacking fully human leukocyte antigen (HLA)-matched donors. However, it still remains unclear which type of graft source is better for SAA patients underwent haplo-HSCT.

Objectives: This study aimed to assess the clinical outcomes of haplo-HSCT using granulocyte colony-stimulating factor (G-CSF)-primed peripheral blood (G-PB) as the graft source, comparing them to a control group receiving G-CSF-primed bone marrow (BM) plus G-PB (BM+PB).

Study design: This was a single-center, retrospective, case-pair cohort study. Between January 2020 and December 2023, a total of 278 consecutive SAA patients received haplo-HSCT in Peking University People's Hospital. In total, 22 patients receiving haplo-HSCT using PB were included in this study. To minimize the impact of potential confounders in this study, we used the propensity score matching (PSM) method to match patients who underwent haplo-HSCT with G-PB plus G-BM at the same time with a 3:1 ratio using nearest-neighbor matching. In the end, 88 patients were included in this study. A total of 22 patients received PB stem cells as graft and 66 patients received G-CSF-primed BM plus PB as graft.

Results: The PB group demonstrated greater neutrophil (100% vs. 93.9%, P = .04) and platelet engraftment (95.5% vs. 89.0%, P = .03) incidence compared with the BM+PB group. There were no significant differences in the cumulative incidences of grades II-IV (13.6% vs. 25.8%, P = .28) or grades III-IV acute graft-versus-host disease (aGVHD; 4.5% vs. 4.6%, P = .99) between the PB group and BM+PB group. The PB group (36.7%) exhibited a trend toward a higher incidence of chronic GVHD compared to BM+PB group (24.1%). However, the difference between the two groups was not statistically significant. Moreover, the immune reconstitution of CD3+T cells, CD4+T cells, CD8+T cells and CD19+B cells were also comparable between two groups. At 3 years post-haplo-HSCT, the probabilities of overall survival (OS), failure-free survival (FFS), and GVHD-free/failure-free survival (GFFS) were 86.1% versus 87.9% (P = .90), 86.1% versus 83.3% (P = .73) and 76.5% versus 75.2% (P = .70) for PB and BM+PB group, respectively. In univariate analysis, the graft source did not influence the clinical outcomes after HSCT.

Conclusions: This study illustrated the safety and efficacy of haplo-HSCT with PB being the single graft source as the treatment for SAA, providing a basis for further potential optimization of the current protocol. In the future, this conclusion should be further tested by prospective randomized trials.