Haploidentical stem cell transplantation (HaploSCT) for patients with acute leukemia-an update on behalf of the ALWP of the EBMT.

Allogeneic stem cell transplantations (alloSCT) from haploidentical (>2 HLA mismatch) donors (HaploSCT) are constantly increasing in Europe. From 2005 to 2015 numbers of HaploSCT increased by close to 300%. In parallel, there is a major shift from T deplete (CD34+ megadose) to T replete (non-T deplete) HaploSCT. Graft versus host disease (GVHD) prophylaxis also changed from CD34+ cell purifications to anti-thymocyte globulin (ATG) and lately to post-transplantation cyclophosphamide (PTCy). Novel conditioning regimens have been developed incorporating novel drugs and innovative approaches. Results are persistently improving and currently, registry-based and single-center studies showed no statistical significance difference in transplantation outcome between HaploSCT to alloSCT from unrelated donors and even from HLA-matched sibling donors, although the numbers of those studies are small and the lack of randomized studies available so far. HaploSCT have several advantages and such as the possibility to choose between different potential donors. Parameters to consider in the Haplo donor selection are age, gender, kinship, ABO blood group, CMV status, non-shared HLA Haplotypes and killer cell immunoglobulin-like receptor (KIR). Future goals are to further decrease transplant-related mortality currently mainly due to infection complications and reduce relapse rates especially in patients with high-risk acute leukemia.