The impact of HLA matching on unrelated donor hematopoietic stem cell transplantation in Korean children

BACKGROUND The impact of HLA matching on outcomes of unrelated donor (URD) hematopoietic stem cell transplantation (HSCT) varies in different racial or ethnic groups. Since little is known about the impact of such matching on URD HSCT in Korean children, we analyzed this issue. METHODS We analyzed the outcomes of 142 patients who underwent URD HSCT at 4 Korean medical centers. All patient donor pairs were fully typed for HLA-A, -B, -C, and -DR alleles. RESULTS At a median follow-up of 22 months, 3-year survival rates for patients with 8, 7, and ≤6 matched alleles were 88.4%, 70.7%, and 53.6%, respectively. A single mismatch (Mm) at HLA-B or -C was associated with lower survival compared with that associated with 8 matched alleles. No significant differences were observed between single-allele and single-antigen Mms with respect to survival rate or acute graft-versus-host disease (aGVHD) incidence rates. HLA disparity had a greater impact on the survival of patients with high-risk malignancy than of those with low-risk malignancy. Among pairs with a single Mm, only locus A showed a significant association and higher risk of grade III-IV aGVHD compared to those in patients with 8 matched alleles. CONCLUSION Disparity in HLA class I, regardless of antigen or allele Mm, adversely affected both survival and grade III-IV aGVHD development. An increased number of HLA Mms was associated with a higher risk of post-transplantation complications. Further investigations using larger cohorts are required to confirm the effects of HLA mismatching on URD HSCT patient outcomes.