Fludarabine combined with treosulfan or total body irradiation as a conditioning therapy before allogeneic hematopoietic stem cell transplantation in acute lymphoblastic leukemia. A retrospective matched-pair analysis from the ALWP of the EBMT.

There are very limited data on treosulfan (Treo)-based conditioning before allogeneic hematopoietic stem cell transplantation (alloHSCT) in acute lymphoblastic leukemia. We aimed to compare fludarabine with Treo (FluTreo) or total body irradiation (FluTBI) in this setting. The final matched-pair analysis included ALL patients transplanted in complete remission after FluTreo (n = 153) or FluTBI (n = 431). The median patient age was 56.5 and 54.1 years, respectively. The allograft was derived from an unrelated (54.2% in FluTreo and 52% FluTBI group), matched sibling (30.7% and 32.5%) or haploidentical donor (15% and 15.5%). The incidence of acute graft-versus-host disease (GVHD) grade II-IV was 26.6% in the FluTreo and 30% in the FluTBI group (p = 0.43). The 2-year incidence of chronic GVHD was 33.5% and 40.7%, respectively (p = 0.23). The 2-year incidence of relapse and non-relapse mortality was 28.1% and 25.6% in the FluTreo and 25.1% and 20.4%, respectively, in the FluTBI group (p = 0.15 and p = 0.38). Leukemia-free survival and overall survival was 46.2% and 55% in the FluTreo and 54.5% and 61.3%, respectively, in the FluTBI group (p = 0.1 and p = 0.22). GVHD-free and relapse-free survival was 33.7% and 40.8%, respectively, in FluTreo and FluTBI patients (p = 0.06). In conclusion, there were no significant differences in transplant outcomes between the studied groups.