The impact of human leukocyte antigen (HLA) mismatching at the HLA-A, -B, -C, and -DRB1 loci after unrelated bone marrow transplantation in paediatric patients with haematological malignancies has not been fully examined. Here, we analysed patients with haematological malignancies (all aged ≤15 years; n = 1330) who underwent a first unrelated bone marrow transplantation between 1993 and 2017 in Japan. The results show that although an HLA mismatch was significantly associated with a low relapse rate, it was also associated with higher non-relapse mortality. There was a significant association between HLA mismatch and low overall survival. Locus mismatch analysis revealed that, as in adults, an HLA-C mismatch had a significant negative impact on survival; however, in paediatric patients, an HLA-DRB1 mismatch did not have a negative impact, although these HLA mismatch effects are weakened in recent cases. Taken together, the results suggest that an HLA-matched donor should be the first candidate for paediatric patients; however, for patients without a matched sibling or matched unrelated donor, we can select an unrelated donor with a mismatch at HLA-DRB1 if available.
Keywords: HLA mismatch; haematological malignancy; paediatrics; unrelated bone marrow transplantation.
© 2022 British Society for Haematology and John Wiley & Sons Ltd.