Which donor is better when a matched donor is not available domestically? Comparison of outcomes of allogeneic stem cell transplantation with haploidentical and international donors in a homogenous ethnic population
Introduction
The survival rate for patients with hematologic malignancies has been greatly improved by the development of targeted therapy, immunotherapy, and transplantation [[1], [2], [3]]. Particularly, allogeneic stem cell transplantation (alloSCT) has been identified as a curative treatment modality in hematologic malignancies [2], improving the 3-year overall survival (OS) of leukemia patients to 60–70% [[4], [5]].
Traditionally, human leukocyte antigen (HLA)-matched related donors (MRD) are selected for alloSCT due to the superior outcomes compared with those from unrelated or HLA-mismatched donors. However, with the use of T-cell-depleted modalities, including prophylactic antithymocyte globulin (ATG) and post-transplantation cyclophosphamide (postCy), survival outcomes with alloSCT from unrelated or haploidentical donors have improved dramatically, approximating the survival outcomes of alloSCT from MRD [[6], [7]].
In practice, the probability of finding MRD is limited to only 25% for patients who have one sibling. With the decrease in birthrate in developed countries, donor sources other than MRD, particularly, unrelated matched donors, are increasingly being used for alloSCT. In South Korea, unrelated donor sources for alloSCT are identified by the Korean Marrow Donor Program (KMDP). In patients for whom there are no appropriate MRD or unrelated donors from the KMDP, haploidentical or international donors are used for alloSCT. However, it is not known which donor is better for alloSCT in this homogeneous ethnic country.
Here, we performed a multicenter retrospective study at four hospitals in South Korea to compare the survival outcomes and complications of patients with hematologic malignancies (myelodysplastic syndrome [MDS]/acute leukemia) undergoing alloSCT from haploidentical and international donors.
Section snippets
Patient population
We retrospectively recruited patients diagnosed with MDS and acute leukemia who had undergone alloSCT from either haploidentical or international donors at Seoul National University Hospital, Samsung Medical Center, Kyungpook National University Hospital, and the National Cancer Center between December 2002 and April 2016. The alloSCTs performed during this time were divided into those occurring during an early period (December 2002 through October 2009) and a late period (November 2009 through
Patient characteristics
Of the 176 patients included in the study, 121 underwent alloSCT from haploidentical-related donors and 55 had international donors from Taiwan (n = 14), the United States of America (n = 13), Japan (n = 11), China (n = 10), Germany (n = 1), and Australia (n = 1); countries of origin were not recorded from five donors. The baseline clinical characteristics of the patients receiving transplants from either international or haploidentical donors were compared and are summarized in Table 1. There
Discussion
In many developed countries, including South Korea, finding MRD for alloSCT has become more difficult, as most patients have no or only one sibling because of lower birthrates. Therefore, alternative donor sources have received attention for alloSCT. As one alternative, umbilical cord blood can be used for alloSCT. The use of higher doses of infused cells and the development of supportive care have improved the 2-year OS of patients receiving cord blood transplantations to 53% [9]. However, the
Acknowledgement
We offer thanks to our patients.
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These authors contributed equally.