ABO mismatch increases transplant-related morbidity and mortality in patients given nonmyeloablative allogeneic HPC transplantation

BACKGROUND: ABO mismatch has not been thought to affect the outcome of patients undergoing myeloablative conditioning and allogeneic HPC transplantation. Data on transplant‐related complications after ABO‐mismatched transplantation after nonmyeloablative conditioning are limited. STUDY DESIGN AND METHODS: Therefore, 40 patients were analyzed after nonmyeloablative conditioning with regard to ABO compatibility. Eleven received a minor and bidirectional and 8 a major ABO‐mismatched graft. RESULTS: Four patients had evidence of hemolysis during engraftment, being lethal in one, and three developed pure RBC aplasia. Six patients in the ABO‐mismatched group developed thrombotic microangiopathy, and three of them died. ABO‐identical and ABO‐mismatched patients had a similar incidence of GVHD. Viral infections occurred in both groups in equal shares. Patients with an ABO‐mismatch had to be rehospitalized until Day 100 for a median of 19 days versus 0 days in the identical group (p < 0.05). Overall survival was 60 and 57 percent in the ABO‐identical and ABO‐mismatch groups, respectively. The probability of transplant‐related mortality was 0 versus 28 percent in the identical group compared to patients with an ABO mismatch (p < 0.05). The probability of relapse or progression was 76 versus 25 percent in the ABO‐identical group compared to the ABO‐mismatched group, respectively. CONCLUSION: Significantly more patients with ABO mismatch showed transplant‐associated complications and died as a result of transplant‐related causes.