Allogeneic haemopoietic transplantation for acute myeloid leukaemia in second complete remission: a registry report by the Acute Leukaemia Working Party of the EBMT.

Allogeneic haemopoietic cell transplant (allo-HCT) may be curative in acute myeloid leukaemia (AML) in second complete remission (CR2) but the impact of reduced intensity (RIC) versus myeloablative conditioning (MAC) is uncertain. The Acute Leukaemia Working Party of the European Society for Blood and Bone Marrow Transplantation Registry studied an AML CR2 cohort characterised by age ≥ 18 years, first allo-HCT 2007-2016, available cytogenetic profile at diagnosis, donors who were matched family, volunteer unrelated with HLA antigen match 10/10 or 9/10 or haplo-identical. The 1879 eligible patients included 1010 (54%) MAC allo-HCT recipients. In patients <50 years (y), two year outcomes for MAC vs RIC allo-HCT were equivalent with leukaemia-free survival (LFS) 54% for each, overall survival (OS), 61% vs 62%, non-relapse mortality (NRM) 18% vs 15% and graft versus host disease relapse-free survival (GRFS) 38% vs 42%. In patients ≥50 y, 2 y outcomes for MAC vs RIC allo-HCT were equivalent for LFS 52% vs 49%, OS 58% vs 55% and GRFS 42.4% vs 36%. However, NRM was significantly inferior after MAC allo-HCT, 27% vs 19% (P = 0.01) despite worse cGVHD after RIC-allo (32% vs 39%). These data support the need for ongoing prospective study of conditioning intensity and GVHD mitigation in AML.