Early Post-Transplant Minimal Residual Disease Assessment Improves Risk Stratification in Acute Myeloid Leukemia

We studied if the inclusion of early post–stem cell transplantation (SCT) minimal residual disease (MRD) assessments improved prognostication in patients with acute myeloid leukemia (AML). Two hundred sixty-nine AML patients in morphological complete remission (CR) who underwent a first SCT were included if they had evaluable pre-SCT MRD assessment by multiparametric flow cytometry. Post-SCT MRD assessments were performed at days +30, +100, and +180. The primary outcome was 1-year relapse incidence (RI). Of 269 patients in CR, 83 (30.8%) had detectable MRD pre-SCT. Post-SCT, during routine disease assessment time points, 9 of 241 evaluable patients (3.7%) at day +30, 6 of 191 evaluable patients (3.1%) at day +100, and 4 of 133 evaluable patients (3%) at day +180 were MRD positive while in CR. MRD positivity at day +30 predicted the highest risk of relapse at 1 year (group 1, 1-year RI 78%). Among MRD-negative patients at day +30, either adverse risk category by European Leukemia Net (ELN) or intermediate risk who were aged ≥60 years and/or pre-SCT MRD-positive represented the intermediate-risk group (group 2, 1-year RI 29%). The remaining patients represented the low-risk group (group 3, 1-year RI 5%). For patients in CR beyond day +30 post-SCT, detectable MRD at any time point predicted impending relapse within 2 months. Early post-SCT MRD assessment—combined with pre-SCT MRD assessment, ELN risk category, and age—improves risk stratification for relapse in AML patients post-transplant. Studies aimed at preventing impending relapse in this high-risk population are urgently needed.