The value of measurable residual disease (MRD) in elderly patients with acute myeloid leukemia (AML) is inconsistent between those treated with intensive vs hypomethylating drugs, and unknown after semi-intensive therapy. We investigated the role of MRD in refining complete remission (CR) and treatment duration in the phase 3 FLUGAZA clinical trial, which randomized 283 elderly AML patients to induction and consolidation with fludarabine plus cytarabine (FLUGA) vs 5-azacitidine. After consolidation, patients continued treatment if MRD was ≥0.01% or stopped if MRD was <0.01%, as assessed by multidimensional flow cytometry (MFC). On multivariate analysis including genetic risk and treatment arm, MRD status in patients achieving CR (N = 72) was the only independent prognostic factor for relapse-free survival (RFS) (HR, 3.45; P = .002). Achieving undetectable MRD significantly improved RFS of patients with adverse genetics (HR, 0.32; P = .013). Longer overall survival was observed in patients with undetectable MRD after induction though not after consolidation. Although leukemic cells from most patients displayed phenotypic aberrancies vs their normal counterpart (N = 259 of 265), CD34 progenitors from cases with undetectable MRD by MFC carried extensive genetic abnormalities identified by whole-exome sequencing. Interestingly, the number of genetic alterations significantly increased from diagnosis to MRD stages in patients treated with FLUGA vs 5-azacitidine (2.2-fold vs 1.1-fold; P = .001). This study supports MRD assessment to refine CR after semi-intensive therapy or hypomethylating agents, but unveils that improved sensitivity is warranted to individualize treatment and prolong survival of elderly AML patients achieving undetectable MRD.
Clonal evolution in acute myeloid leukemia (AML) originates long before diagnosis and is a dynamic process that may affect survival. However, it remains uninvestigated during routine diagnostic workup. We hypothesized that the mutational status of bone marrow dysplastic cells and leukemic blasts, analyzed at the onset of AML using integrated multidimensional flow cytometry (MFC) immunophenotyping and sorting (FACS) with next-generation sequencing (NGS), could reconstruct leukemogenesis. Dysplastic cells were detected by MFC in 285 of 348 (82%) newly-diagnosed AML patients. Presence of dysplasia according to MFC and WHO criteria had no prognostic value in the elderly. NGS of dysplastic cells and blasts isolated at diagnosis identified three evolutionary patterns: stable (n=12/21), branching (n=4/21) and clonal evolution (n=5/21). In patients achieving complete response, integrated MFC and FACS with NGS showed persistent measurable residual disease (MRD) in phenotypically normal cell types, as well as the acquisition of genetic traits associated with treatment resistance. Furthermore, whole-exome sequencing of dysplastic and leukemic cells at diagnosis and of MRD uncovered different clonal involvement in dysplastic myelo-erythropoiesis, leukemic transformation and chemoresistance. Altogether, we showed that it is possible to reconstruct leukemogenesis in approximately 80% of newly diagnosed AML patients, using techniques other than single-cell multiomics.
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