Retrospective study on the effect of non inherited maternal antigen transplantation related mortality in HLA mismatched cord blood transplantation: Hong Kong’s experience

Abstract

Aim: Transplantation-related mortality (TRM) is well-recognized complication of HLA-mismatched cord blood transplantation (CBT). In utero, non-inherited maternal antigen (NIMA) is exposed and recognized by the fetus, which induces T regulator cells to the antigens. It is conceivable that the matching of donor NIMAs in CBTs may alleviate some of the excess mortality associated with this treatment in the recipients. We aim to review if the same concept is observed in the CBTs performed in two paediatric haematopoietic stem cell transplantation centers in Hong Kong.

Methods: A retrospective analysis was performed and a review of the total of 41 paediatric CBTs performed for haematological malignancies from January 2008 to December 2017 in Hong Kong when the maternal blood samples could be retrieved for HLA typing.

Results: Only 4 NIMA-matched CBTs for haematological diseases (i.e., the NIMA of the donor cord blood units (CBUs) matched to the patient) were identified and the remaining 37 were non-NIMA-matched CBTs. Due to the small sample size, cases and controls were unable to match on age, disease, disease status, transplantation-conditioning regimen, HLA matching status, and infused cell dose. Two out of 4 (50%) recipients NIMA-matched CBTs died of engraftment failure and disease relapse while 25 out of 37 (68%) non-NIMA-matched died. TRM was similar after NIMA-matched UCBTs compared with NIMA-mismatched CBTs. Overall survival was not higher after NIMA-matched CBT. The 3-year probability of overall survival rates were 50% after NIMA-matched CBTs and 32% after NIMA-mismatched CBTs.

Conclusions: This retrospective study demonstrated better outcome of NIMA-matched CBTs as compared with NIMA-mismatched CBTs however limited by small sample size and wide variation in the patients’ parameters. When facing the choice of multiple HLA-mismatched CBUs containing adequate cell doses, the advantage of selecting NIMA-matched CBUs on improving survival after mismatched CBT requires further collection of data and experimental evidence.