For patients with an indication for allogeneic HCT, the search for a stem cell donor is a challenge. 20% of patients who need an allograft have an HLA-identical sibling available, and for approximately 70% of the remaining patients, a suitable, HLA-well-matched (10/10), unrelated volunteer can be found. For the remaining patients, partially matched (single mismatch) unrelated donors or haploidentical donors are alternative options.~Recently published retrospective single center and registry studies suggest comparable outcomes for HCT from unrelated donors matched at HLA -A, -B, -C, and -DRB1 and haploidentical donors. The number of haploidentical HCT evaluated in these studies was still relatively small and a selection bias for the retrospective comparisons cannot be excluded.~The goal of this trial is to evaluate overall survival of patients with high-risk AML, ALL or MDS after partially matched unrelated or haploidentical donor transplantation..
The goal of this trial is to compare the outcome after partially matched (single mismatch) unrelated donor transplantation with haploidentical transplantation in a randomized controlled setting.