Improved Outcome in Young Children Compared to Adolescents and Adults After Allogeneic Hematopoietic Stem Cell Transplant for Acute Myeloid Leukemia: a Retrospective Study From Francophone Society of Bone Marrow Transplantation and Cell Therapy (SFGM-TC) (SFGM-TC)

Background: There are currently few data on the outcome of acute myeloid leukemia (AML) in adolescents and young adults (AYAs) after allogeneic HSCT. The aim of this study is to describe the outcome and its specific risk factors for children, AYAs and adults after a first allogeneic HSCT for AML. Methods: In this retrospective study, we compared the outcome of AML patients receiving a first allogeneic HSCT between 2005 and 2017 according to their age at transplantation’s time: children (<15 years, n=564), AYAs (15-25 years, n=647) and adults (26-40 years; n= 1434). Results: With a median follow-up of 4.37 years (min-max 0.18 – 14.73 years), the probability of 2 year-overall survival (OS) was 71.4% in children, 61.1% in AYAs and 62.9% in adults (p=0.0009 for intergroup difference). Both relapse and non-relapse mortality (NRM) Cumulative Incidence (CI) estimated at 2 years were different between the age groups (30.8% for children, 35.2% for AYAs and 29.4% for adults - p=0.0254, and 7.0% for children, 10.6% for AYAs and 14.2% for adults, p<0.0001; respectively). Whilst there was no difference between the 3 groups for grade I to IV acute GVHD CI at 3 months, the chronic GVHD CI at 2 years was higher in AYAs and adults (31.4% and 36.4%, respectively) in comparison to the children (17.5%) (p<0.0001). In multivariable analysis, factors associated with death were AML cytogenetics (HR1.73 [1.29-2.32] for intermediate risk 1, HR 1.50 [1.13-2.01] for intermediate risk 2, HR 2.22 [1.70-2.89] for high cytogenetics risk compared to low risk), use of TBI ≥ 8 Grays (HR 1.33 [1.09-1.61]), disease status at transplant (HR 1.40 [1.10-1.78] for second Complete Remission (CR), HR 2.26 [1.02-4.98] for third CR and HR 3.07 [2.44-3.85] for active disease, compared to first CR), graft source (HR 1.26 [1.05-1.50] for Peripheral Blood Stem Cells compared to Bone Marrow) and donor age (HR 1.01 (1-1.02] by increase of one year). Conclusion: Age is an independent risk factor for NRM and extensive chronic GVHD. This study suggests that AYAs AML patients should be treated with chemotherapy-based MAC regimen and bone marrow as stem cells source.