Allogeneic Hematopoietic Cell Transplantation with Myeloablative Conditioning Regimen of Reduced Toxicity Is Associated with Favorable Survival in Patients with Secondary Acute Myeloid Leukemia

Background: Secondary or treatment-related acute myeloid leukemia (sAML) is associated with poor outcomes. Although allogeneic hematopoietic cell transplantation (alloHCT) is the treatment of choice, patient eligibility criteria and optimal conditioning regimen remain under study. We have previously shown an advantage of a myeloablative conditioning regimen with reduced toxicity (Fludarabine 150mg/m2, Treosulfan 42g/m2, FluTreo) compared to a reduced intensity regimen. However, the long-term effects of this regimen remain unknown, especially in comparison to patients not receiving alloHCT. Aims: We hypothesized that patients transplanted with FluTreo would have a long-term survival advantage over other treatment alternatives. Methods: We retrospectively studied consecutive patients treated for sAML in our center over the last two decades (1998-2018). Exclusion criteria were: age>70 years, ECOG performance status≥3 at presentation, induction regimens≤2, and autologous or haploidentical HCT because these were performed in individual patients. Since 2013, we have introduced FluTreo for patients with a suitable donor that would have been previously eligible only for reduced intensity conditioning/RIC. The following factors were studied in the whole cohort: age, type of disease (treatment-related or post myelodysplastic syndrome/MDS), previous intensive chemotherapy cycles, cytogenetic risk, overall (OS) and disease-free survival (DFS). In transplant recipients, we also recorded HCT-comorbidity index/CI score, cumulative incidence (CI) of graft-versus-host disease (GVHD), and treatment-related mortality (TRM). Follow-up was calculated from diagnosis in the whole cohort; and from date of transplant in the sub-group analysis of transplant recipients. Results: We studied 19 FluTreo recipients compared to 46 recipients of other conditioning regimens (38 myeloablative and 8 RIC), and 52 patients treated only with chemotherapy. Complete remission (CR) had been achieved in all FluTreo recipients before HCT, compared to 53% of other transplants, and 44% of chemotherapy only patients (p