Prognosis Value of Measurable Residual Disease By Multiparameter Flow Cytotometry in Patients with Acute Myeloblastic Leukemia Prior to Allogeneic Hematopoietic Cell Transplantation

Introduction: Acute myeloblastic leukaemia (AML) is an heterogeneous disease with different molecular and prognostic characteristics. According to the comorbidities and the revised 2017 European Leukaemia genetic risk stratification (ELN17), allogeneic hematopoietic cell transplantation (HCT) is the best therapeutic option for many patients with AML (Grimm, Blood Adv 2020). However, relapse remains the main cause of mortality after transplantation. Impact of MRD on the outcome of patients is well recognized and ELN2017 introduced the new response category complete remission (CR) without MRD (Döhner H, Blood 2017). Detection of measurable residual disease (MRD) by multiparameter flow cytometry (MFC) in AML before allogeneic HCT could be a powerful predictor of outcome and decisive when establishing strategies that modify the prognosis of these patients. Methods: Retrospective multicentre analysis of MRD by MFC of patients undergoing transplantation allogeneic in 4 centres during the period from 2012 to 2020. Both Leukaemia Associated Aberrant Immunophenotype (LAIP) and different from normal (DFN) approach were used to analyse the MRD. The MRD was carried out with 8-color panels based on Euroflow protocols. The samples were acquired in 8-color digital cytometers (FACSCanto II) calibrated and compensated according to Euroflow protocols. Results: 295 of 318 patients were evaluated. Table 1 shows the characteristics of the patients. 285 (96.7%) were in complete remission (CR), 207 had negative MRD, in 21 MRD was less than 0.1% (MRD-low) and in 57 greater than or equal to 0.1% (MRD-high). At 2 years, the overall survival (OS) and leukaemia-free survival (LFS) in the whole group were 69% (95% CI 63.18-74.18) and 58.4% (95% CI 52.4-63.9) respectively. In CR patients, MRD levels significantly influenced on outcomes, with OS and LFS of 76.7% and 67.6% for negative MRD, 68.5% and 49.7% MRD-low and 50 % and 36.6% in MRD-high, p