Impact of anti-HLA antibodies on allogeneic hematopoietic stem cell transplantation outcomes after reduced-intensity conditioning regimens

Anti-human leukocyte antigen (HLA) antibodies are associated with several complications in solid organ transplantations, but their impact after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is not yet well defined. To evaluate the relevance of anti-HLA antibodies, we have retrospectively analyzed 107 peripheral blood allo-HSCTs after reduced-intensity conditioning regimen between 2005 and 2010. Acute myeloid leukemia and multiple myeloma were the most frequent malignancies in the cohort. The detection of anti-HLA antibodies was systematically performed in all patients before transplantation. Anti-HLA antibodies were present in 24 patients (22%). There was no significant impact of anti-HLA antibodies on engraftment, incidence of relapse, and incidence of acute graft-vs-host disease. The presence of anti-HLA antibodies was associated with significantly worse overall survival (p = 0.006) and event-free survival (p = 0.024) after stratification on sex. The 3-year probability of overall survival was 34% without anti-HLA antibodies and 16% in their presence. Patients with anti-HLA antibodies had a higher transplant-related mortality associated with life-threatening vascular complications. Our study supports that anti-HLA antibodies should be tested and considered as an important impacting factor for transplantation outcomes after reduced-intensity conditioning allo-HSCT. We recommend its consideration before allo-HSCT in the donor-recipient selection parameters.