HAPLOIDENTICAL TRANSPLANT WITH POST-TRANSPLANT CYCLOPHOSPHAMIDE FOR ACUTE MYELOID LEUKAEMIA AND MYELODYSPLASTIC SYNDROMES PATIENTS: THE ROLE OF PREVIOUS LINES OF THERAPY.

Background: Allogeneic haematopoietic stem-cell transplant is a potentially curative option for high-risk acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS) patients. Post-transplant cyclophosphamide administration allows for selection of haploidentical donors in patients who are eligible for the procedure, but do not have a fully matched donor, since it can overcome the HLA barrier. There is still an active debate on whether intensification of the conditioning regimen is necessary with haploidentical donors when peripheral blood stem cells are used as the source of the graft.   Herein we report our decennial experience of haploidentical stem-cell transplant using peripheral blood stem cells at King’s College Hospital. Objectives: The primary objective was to evaluate overall survival (OS) for patients with less than two previous lines of therapy. Secondary objectives were total OS, OS according to cytomegalovirus (CMV) reactivation, incidence of transplant-related mortality (TRM), graft-versus-host disease (GVHD) and GVHD-relapse-free survival (GRFS). Results: One-year and three-year total OS were 62% and 43%, respectively, with a median OS of 22 months. One-year and three-year OS for patients with ≤2 and in patients with >2 previous lines of therapy were 72% and 55%, and 60% and 22%, respectively (p-value=0.04). The median OS in patients with >2 previous lines of therapy and ≤2 lines of therapy was 16 and 49 months, respectively. Cumulative incidence (CI) of relapse was 25% with a median time to relapse of 5 months (range 1 – 38 months). Conclusions: Haploidentical haematopoietic stem-cell transplant is potentially curative in chemo-sensitive AML and MDS and offers a high rate of prolonged remission. Our cohort further confirms the role of consolidative haploidentical transplant in patients in complete remission and highlights that patients with heavily pre-treated disease may not benefit from this strategy.