Influence of One Human Leukocyte Antigen Mismatch on Outcome of Allogeneic Bone Marrow Transplantation from Related Donors

This study compares the clinical outcomes of 60 consecutive patients who received an allogeneic blood or marrow stem cell transplant (BMT) from one Human Leukocyte Antigen (HLA) mismatched related donors with those of 120 matched patients who had HLA identical sibling donors. The control patients were matched for diagnosis, disease status, conditioning regimen, and age at BMT. All patients received standard CYA and MTX for GVHD prophylaxis. The probability of overall survival (OS) at 5 years was 35% in the study group compared to 56% in the control group. The relapse rates and acute GVHD rates did not differ between the two groups. Graft failure was a significant problem in the study group compared to the control group (13 vs. 0%, p < 0.0001). All cases of graft failure occurred in patients with a mismatch in the host-versus-graft direction. BMT-related deaths were also increased in the study group. Forty percent of deaths were caused by infection in the study group vs. 19% in the control group (p < 0.01). In conclusion, the OS of patients receiving marrow/stem cells from one antigen mismatched related donors was inferior to that of controls with HLA-identical related donors. There was an increase in mortality related to infections occurring in the setting of an increased frequency of graft failure in these patients.