Outcomes of 544 Patients with t(6;9)/DEK::NUP214 acute myeloid leukemia undergoing allogeneic stem cell transplantation: an EBMT study on behalf of the acute leukemia working party (ALWP) and the pediatric diseases working party (PDWP).

Acute myeloid leukemia (AML) with translocation (6;9)(p23;q34) is a rare and high-risk disease, frequently co-occurring with FLT3-ITD alteration. We retrospectively analyzed 544 patients with t(6;9) AML undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) and reported to the EBMT registry, between 2000 and 2022. At 2-years, overall survival (OS), leukemia-free survival (LFS), relapse incidence (RI), non-relapse mortality (NRM) and GVHD-free/relapse-free survival (GRFS) were 65.7%, 59.1%, 23.0%, 17.9% and 45.6% respectively. The 431 patients transplanted in first complete remission (CR1) had more favorable OS (71.7%), LFS (65.8%) and RI (18.2%). Pediatric and adolescent/young adult (AYA, ≤ 39 years) patients in CR1 had improved outcomes. In patients ≥ 40 years old, OS, LFS, and NRM gradually worsened, whereas significant increase in RI and decrease in GRFS were observed after 53 years. In a matched-pair analysis performed on 76 FLT3-ITD positive and 76 negative CR1 patients, FLT3-ITD was associated with an approximately three-fold higher RI risk, without differences in OS. In conclusion, allo-HSCT in t(6;9) AML provides relatively favorable outcomes especially when performed in CR1. Pediatric and AYA patients derived the greatest benefit from transplant. FLT3-ITD positivity remains a relevant risk factor for relapse, though without impact on OS.