Early blast clearance during sequential conditioning prior to allogeneic stem cell transplantation in patients with acute myeloid leukaemia.

For patients with relapsed or refractory AML, sequential conditioning prior to allogeneic stem cell transplantation (alloSCT) is an established and potentially curative treatment option. Early response to treatment during conditioning indicates chemotherapy-responsive disease and may have prognostic value. We retrospectively evaluated blast clearance on day 5 after melphalan, administered 11 days prior to alloSCT as part of a sequential conditioning in 176 patients with active AML. Overall survival (OS) was 52% (95% confidence interval [CI] 45%-60%), and relapse-free survival (RFS) was 47% (95% CI 40%-55%) at 3 years. Patients who achieved early blast clearance did not show a significant improvement in OS and RFS (OS, hazard ratio [HR] HR 0.75, p 0.19; RFS, HR 0.71, p 0.09, respectively), but had a significantly lower non-relapse mortality rate (HR 0.46, p 0.017). HLA-mismatched donor, older age, adverse genetic risk and higher comorbidity scores were associated with inferior survival outcomes. A high initial blast count was only associated with inferior prognosis in patients receiving chemotherapy-only compared to total body irradiation containing conditioning therapy. These results indicate that for patients transplanted with active AML, sensitivity to chemotherapy might be of less importance, compared to other disease- and transplant-related factors.

Comparable outcomes for TBI-based versus treosulfan based conditioning prior to allogeneic hematopoietic stem cell transplantation in AML and MDS patients.

Allogeneic hematopoietic stem cell transplantation (allo-HCT) is a standard treatment for patients with AML and MDS. The combination of fractionated total body irradiation(8GyTBI/Flu) with fludarabine is an established conditioning regimen, but fludarabine/treosulfan(Flu/Treo) constitutes an alternative in older/comorbid patients. We conducted a retrospective analysis of 215 AML(in CR) and 96 MDS patients undergoing their first allo-HCT between 2011 and 2022, identifying 53 matched Flu/Treo and 8GyTBI/Flu patients through propensity score matching. Median follow-up of survivors was 3.3 years and 4.1 years. For the Flu/Treo group, 1-year non-relapse mortality (2% vs. 10%, p = 0.03) was lower, while 1-year relapse incidence (16% vs. 13%, p = 0.81) was similar. Three-year outcomes, including relapse-free survival and graft-versus-host disease incidence, were comparable (OS: 81% vs. 74%, p = 0.70; RFS: 78% vs. 66%, p = 0.28; chronic GvHD: 34% vs. 36%, p = 0.97; acute GvHD (100 days): 11% vs. 23%, p = 0.11). Multivariable analysis, considering age, ECOG, HCT-CI, and MRD status, revealed no associations with main outcomes. Dose-reduced conditioning with Flu/Treo or 8GyTBI/Flu demonstrated favorable and comparable survival rates exceeding 70% at 3 years with 1-year NRM rates below 10% and low relapse rates in the matched cohort. These data underline the need for further evaluation of TBI and Treo-based conditionings in prospective trials.