Multicenter retrospective analysis of bone marrow graft versus peripheral blood graft in haploidentical HSCT

The use of peripheral blood (PB) versus bone marrow (BM) stem cell graft in haploidentical hematopoietic stem cell transplantation (haplo-HSCT) with post-transplant cyclophosphamide (PTCy) for graft-versus-host disease (GVHD) prophylaxis remains controversial. Moreover, the value of adding anti-thymoglobuline (ATG) to PTCy is unknown. Retrospective propensity score matched analysis of 1344 adult patients receiving haplo-HSCT at 37 centers in France found that rates of grade II-IV and grade III-IV acute GVHD were lower with BM than with PB, while adding ATG did not improve the the acute GVHD rates. In the subgroup of acute leukemia, myelodysplastic syndrome, and myeloproliferative syndrome (AL-MDS-MPS) patients receiving non-myeloablative conditioning, risk of relapse was more than two-fold increased with BM versus PB (51% versus 22%) while risk of acute GVHD was higher with PB than with BM (grade II-IV 38% versus 28%; grade III-IV 16% versus 8%). Among AL-MDS-MPS patients receiving intensified conditioning, risk of relapse was similar with PB and BM, but risk of grade III-IV acute GVHD was higher with PB than with BM (HR 2.0; p=0.012).