Outcomes of Different Haploidentical Transplantation Strategies from the Taiwan Blood and Marrow Transplantation Registry

SIMPLE SUMMARY: Haploidentical hematopoietic stem cell transplantation haplo-HSCT is now increasingly recognized as a valid treatment for patients with hematologic malignancies. The two most noteworthy strategies are posttransplantation cyclophosphamide (PTCy) with or without anti-thymoglobulin and granulocyte colony stimulating factor-primed bone marrow plus peripheral blood stem cells (GIAC). Direct comparisons of these approaches are rare, which makes physicians hard to choose the optimal treatment strategy for patients. We used a nationwide blood and marrow transplantation registry to compare these approaches. We found that patients in the modified GIAC (mGIAC) group had the most favorable platelet and neutrophil engraftment kinetics but had a higher extensive chronic graft-versus-host disease rate. The patients receiving mGIAC had the lowest nonrelapse mortality and highest overall survival rates. Physicians can choose the optimal treatment for patients based on the distinct clinical features and outcomes of these strategies. This study may pave the way for further prospective trials. ABSTRACT: Background: The two most noteworthy strategies for haploidentical stem cell transplantation (haplo-HSCT) are posttransplantation cyclophosphamide (PTCy) with or without thymoglobulin (ATG) and granulocyte colony stimulating factor-primed bone marrow plus peripheral blood stem cells (GIAC). We aimed to compare these approaches in patients with hematological malignancies. Methods: We enrolled 178 patients undergoing haplo-HSCT, including modified GIAC (mGIAC), PTCy without ATG, and PTCy with ATG. Results: The patients in the mGIAC group had the most favorable platelet and neutrophil engraftment kinetics. Although the grade III–IV acute graft-versus-host-disease (GvHD) rates were similar, those receiving mGIAC had a significantly higher extensive chronic GvHD rate. The patients receiving mGIAC had a similar cumulative incidence of relapse (CIR) to that in the patients receiving PTCy with ATG, but this was lower than that in the patients receiving PTCy without ATG. The patients receiving mGIAC had the lowest nonrelapse mortality (NRM) and the highest overall survival (OS) rates. The differences in CIR, NRM, and OS remained significant when focusing on patients with low/intermediate-risk diseases before haplo-HSCT. Intriguingly, among patients with high/very-high-risk diseases before haplo-HSCT, no differences were observed in the CIR, NRM, OS, or GvHD/relapse-free survival. Conclusion: the mGIAC approach may yield a better outcome in Taiwanese patients with hematologic malignancies, especially for those with low/intermediate-risk diseases.