Alternative donors for allogeneic hematopoietic stem cell transplantation in poor-risk AML in CR1

Allogeneic hematopoietic stem cell transplantation (alloHSCT) remains the treatment of choice to consolidate remission in patients with poor-risk acute myeloid leukemia (AML). With increasing alternative donors available, the preferred donor or stem cell source is debated. We set out to study outcome in recipients of alloHSCT with poor-risk AML in first complete remission (CR1) by donor type. A total of 6545 adult patients with poor-risk AML in CR1 receiving an alloHSCT using matched related donor (MRD, n = 3511) or alternative donors, including 10/10 (n = 1959) or 9/10 matched unrelated donors (MUDs, n = 549), umbilical cord blood (UCB) grafts (n = 333), or haplo-identical (haplo) donors (n = 193) were compared. Overall survival (OS) at 2 years following MRD alloHSCT was an estimated 59 ± 1%, which did not differ from 10/10 MUD (57 ± 1%) and haplo alloHSCT (57 ± 4%). OS, however, was significantly lower for 9/10 MUD alloHSCT (49 ± 2%) and UCB grafts (44 ± 3%), respectively (P < .001). Nonrelapse mortality (NRM) depended on donor type and was estimated at 26 ± 3% and 29 ± 3% after haplo alloHSCT and UCB grafts at 2 years vs 15 ± 1% following MRD alloHSCT. Multivariable analysis confirmed the impact of donor type with OS following MRD, 10/10 MUD, and haplo alloHSCT not being statistically significantly different. NRM was significantly higher for alternative donors as compared with MRD alloHSCT. Collectively, these results suggest that alloHSCT with MRDs and 10/10 MUDs may still be preferred in patients with poor-risk AML in CR1. If an MRD or 10/10 MUD is not available, then the repertoire of alternative donors includes 9/10 MUD, UCB grafts, and haplo-identical donors. The latter type of donor is increasingly applied and now approximates results with matched donors.