Impact of donor type in patients with AML given allogeneic hematopoietic cell transplantation after low-dose TBI based regimen

Purpose: We assessed the impact of donor type in acute myeloid leukemia (AML) patients transplanted with 2 Gy total body irradiation (TBI)-based nonmyeloablative conditioning regimen. Experimental Design: Data from 1715 adult patients, with AML in CR1 or CR2 were included in this retrospective survey. Results: Donors consisted either of HLA-matched sibling donors (MSD, n=701), 10/10 HLA-matched unrelated donors (MUD, n=611), HLA-haplo-identical donors (haplo, n=112) or single or double umbilical cord bloods (CBT, n=291). Chronic graft-versus-host disease (GVHD) was less frequent in CBT (28%) and in haplo (30%) patients than in MSD (50%) and MUD (51%) recipients (P<0.001). Two-year incidence of relapse was 32%, 30%, 34% and 34% in MSD, MUD, CBT and haplo patients, respectively (P=0.7). Two-year overall (OS) and GVHD-free relapse free survival (GRFS) were 59% and 29% in MSD patients, 56% and 39% in CBT recipients, 53% and 23% in MUD recipients, and 43% and 37% in haplo patients, respectively. In multivariate analyses, MUD patients had lower GRFS than MSD patients beyond day 100 (HR 1.3, P=0.001) while CBT was associated with a better GRFS than MSD beyond day 100 (HR 0.6, P=0.002).  Conclusions: In this large cohort of AML patients transplanted following low-dose TBI-based conditioning the relapse incidence was not affected by donor type suggesting that the intensity of GVL effects might be comparable with these four transplant approaches. Further, CBT was associated with better GRFS beyond day 100 than MSD while the opposite was observed for MUD.

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