Measurable Residual Disease in Acute Myeloid Leukemia Using Flow Cytometry: A Review of Where We Are and Where We Are Going

Abstract

The detection of measurable residual disease (MRD) has become a key investigation that plays a role in the prognostication and management of several hematologic malignancies. Acute myeloid leukemia (AML) is the most common acute leukemia in adults and the role of MRD in AML is still emerging. Prognostic markers are complex, largely based upon genetic and cytogenetic aberrations. MRD is now being incorporated into prognostic models and is a powerful predictor of relapse. While PCR-based MRD methods are sensitive and specific, many patients do not have an identifiable molecular marker. Immunophenotypic MRD methods using multiparametric flow cytometry (MFC) are widely applicable, and are based on the identification of surface marker combinations that are present on leukemic cells but not normal hematopoietic cells. Current techniques include a “different from normal” and/or a “leukemia-associated immunophenotype” approach. Limitations of MFC-based MRD analyses include the lack of standardization, the reliance on a high-quality marrow aspirate, and variable sensitivity. Emerging techniques that look to improve the detection of leukemic cells use dimensional reduction analysis, incorporating more leukemia specific markers and identifying leukemic stem cells. This review will discuss current methods together with new and emerging techniques to determine the role of MFC MRD analysis.

Minimal residual disease monitoring via AML1-ETO breakpoint tracing in childhood acute myeloid leukemia

“…The techniques currently for MRD monitoring of variations in mutant genes are MFC, PCR-based methods, and NGS with limitations [ 13 , 14 ]. To overcome these drawbacks of these methods, we employed ddPCR to achieve accurate and sensitive detection of the AE fusion gene in childhood AML.…”

How to Improve Prognostication in Acute Myeloid Leukemia with CBFB-MYH11 Fusion Transcript: Focus on the Role of Molecular Measurable Residual Disease (MRD) Monitoring

“…Among newer molecular methods, targeted next-generation sequencing (NGS) could provide a complete test of all leukemia-specific genetic aberrations at once, with very high sensitivity. However, NGS data interpretation in MRD monitoring is actually complicated by incurring in some common mutations of any prognostic value but is associated with clonal hematopoiesis of indeterminate potential [69,70]. To note, recent studies have aimed to investigate the clinical relevance of NGS MRD detection, at different timepoints, finding the stronger prognostic impact of NGS MRD status after the first consolidation (2nd timepoint) than at first remission, which could help to identify patient candidates for more aggressive treatment, even when MRD is undetectable by MFC [71].…”

“…The possible presence of resistant leukemic clones or quiescent preleukemic cells, potentially responsible for relapse, could be supposed. The latter, called leukemic-initiating cells (LICs) [83] or leukemic stem cells (LSCs) [58,70], are defined as cells capable of initiating disease, self-renewing, with chemo-resistance properties. This subpopulation, usually CD34+/CD38-, may also contribute to subsequent relapse.…”

New Approaches to Allogeneic Haematopoietic Cell Transplantation

“…However, it is not possible to perform molecular MRD analysis for around 60% of patients with AML, due to a lack of suitable markers for real-time PCR. 87 In order to address this limitation, Thol et al developed an NGS MRD technique that was able to identify a suitable marker in 93% of patients sequenced at the time of diagnosis. 88 Patients who have morphologic complete remission after AML treatment, but ongoing MRD positivity before allo-HCT, have lower OS and PFS outcomes compared with patients who achieve MRD negativity.…”