Use of bone marrow cells is associated with improved outcomes when compared to peripheral blood stem cell after haplo-identical transplants with post transplant cyclophosphamide, a study from of the CTIWP-EBMT.

Few studies analyzed the impact of bone marrow (BM) or peripheral blood stem cells (PBSC) on outcomes after haploidentical transplantation using post-cyclophosphamide (Haplo-PTCY). We analyzed 8854 adults with malignant disorders, given a first Haplo-PTCY. BM cells was used in 2914 and PBSC in 5940 patients. Multivariate models were built adjusting for the statistical differences between the 2 groups. Median follow-up time for survivors in the BM and PBSC groups were 48 and 30 months, respectively. Neutrophil Engraftment was observed in 92.4% of BM and 93.7% of PBSC recipients (p = 0.01). In a multivariate analysis, use of PBSC compared to BM, was associated with higher incidence of acute (HR:1.53; p < 0.0001) and chronic GVHD (HR:1.34; p < 10-3), increased non-relapse mortality (HR:1.22; p = 0.002), similar risk of relapse (HR:1.02; p = 0.79), and decreased overall survival (OS)(HR:1.13; p = 0.008); progression-free survival (PFS)(HR:1.11; p = 0.024) and GVHD-Relapse free survival (GRFS) (HR:1.2; p < 10-3). In conclusion, use of BM cells is associated with better outcomes compared to PBSC after Haplo-PTCY. Future studies should investigate better GVHD prophylaxis in the PBSC-Haplo-PTCY setting and the association of measured T-cell or other subpopulations of lymphocyte content in the PBSC graft.