Abstract: Objective We conducted a retrospective study to evaluate the efficacy of intensified myeloablative conditioning regimen for unrelated donor single-unit umbilical cord blood transplantation (sUCBT) in acute myeloid leukemia with FLT3-ITD mutation.Methods We studied a total of 22 patients with FLT3-ITD positive acute myeloid leukemia undergoing sUCBT between Jun 2012 and Dec 2018 at hematology department, the first affiliated hospital of USTC(Anhui provincial hospital), and evaluated the therapeutic efficacy of intensified myeloablative conditioning regimen without antithymocyte globulin (ATG). Twelve males and 10 females were enrolled. Median age was 24 years (range 4-53) and median weight was 58 kg (range 15-77). Among them, 6 of the patients had NPM1 mutation. Twelve patients were in first complete remission (CR1), three in second complete remission (CR2), and seven in advanced-stage disease before transplantation. All patients received intensified myeloablative conditioning regimen. Four received total body irradiation/ cyclophosphamide/cytosine arabinoside (TBI/Cy/Ara-C). Fifteen received Busulfan/ cyclophosphamide/fludarabine(BU/Cy/Flu). Three received BU/Cy/Ara-C. Ciclosporin A (CsA) in combination with mycophenolate mofetil (MMF) without ATG was used approach to graft-versus-host disease (GVHD) prevention.Results Hematopoietic reconstitution had been achieved successfully in 20/22 patients. The cumulative incidence (CI) of neutrophil engraftment at 42 days was 90.9%, and the median time to engraftment was 17.5 days (range 11~25 days). The CI of platelet engraftment at 120 days was 84.6%, and the median time to engraftment was 37 days (range 20~68 days). Transplant-related complications were collected. Thirteen (59.1%) patients developed pre-engraftment syndrome (PES). Twelve had grade II-IV acute GVHD, and the CI was 54.5%. Six had grade III-IV acute GVHD, and the CI was 27.3%. Four had localized cutaneous chronic GVHD (cGVHD), and the CI at 720 days was 18.2%. No extensive cGVHD occurred. As of June 30, 2020, a median follow-up of 747.5 days（range 6-2 932). Three patients had primary recurrence. The 3-year CI of relapse was 13.6%. The 3-year overall survival and disease-free survival were 62.9% and 63.6% respectively.Conclusion The preliminary investigation of sUCBT with intensified myeloablative conditioning regimen for FLT3-ITD mutation acute myeloid leukemia showed good curative effect, and It is worthy to apply.

Key words: Acute myeloid Leukemia, FLT3-ITD mutation, Umbilical cord blood transplantation