Current and Emerging Techniques for Diagnosis and MRD Detection in AML: A Comprehensive Narrative Review

Abstract

Acute myeloid leukemia (AML) comprises a group of hematologic neoplasms characterized by abnormal differentiation and proliferation of myeloid progenitor cells. AML is associated with poor outcome due to the lack of efficient therapies and early diagnostic tools. The current gold standard diagnostic tools are based on bone marrow biopsy. These biopsies, apart from being very invasive, painful, and costly, have low sensitivity. Despite the progress uncovering the molecular pathogenesis of AML, the development of novel detection strategies is still poorly explored. This is particularly important for patients that check the criteria for complete remission after treatment, since they can relapse through the persistence of some leukemic stem cells. This condition, recently named as measurable residual disease (MRD), has severe consequences for disease progression. Hence, an early and accurate diagnosis of MRD would allow an appropriate therapy to be tailored, improving a patient’s prognosis. Many novel techniques with high potential in disease prevention and early detection are being explored. Among them, microfluidics has flourished in recent years due to its ability at processing complex samples as well as its demonstrated capacity to isolate rare cells from biological fluids. In parallel, surface-enhanced Raman scattering (SERS) spectroscopy has shown outstanding sensitivity and capability for multiplex quantitative detection of disease biomarkers. Together, these technologies can allow early and cost-effective disease detection as well as contribute to monitoring the efficiency of treatments. In this review, we aim to provide a comprehensive overview of AML disease, the conventional techniques currently used for its diagnosis, classification (recently updated in September 2022), and treatment selection, and we also aim to present how novel technologies can be applied to improve the detection and monitoring of MRD.

Minimal Residual Disease in Acute Myeloid Leukemia: Old and New Concepts

“…Currently, qPCR techniques can achieve sensitivities of 10 −4 to 10 −6 [21,23,54]. The use of qPCR is particularly well suited for MRD monitoring in AML cases where a fusion gene or a mutated transcript is highly expressed, which is true in approximately 50% of AML cases [23,54,55].…”

“…Digital PCR is a relatively recent method, developed in the 1990s [99] and first commercialized in the mid-2000s, that allows the absolute quantification of target DNA or RNA sequences in a sample without the need for a reference standard curve to normalize the results, and with good sensitivity [54,100] ranging from 10 −4 to 10 −6 , making it interesting for MRD monitoring in AML.…”

“…Teixeira et al [54], in their review, introduced new potential targets for use in MRD called circulating leukemic cells (CLCs). Unlike their counterparts, circulating tumor cells (CTCs), which derive from solid tumors, the detection of CLCs is still in its early stages but holds promise for estimating MRD.…”

Isolation of acute myeloid leukemia blasts from blood using a microfluidic device

“…CR of the disease is considered when less than 5% of leukemic cells are found in the BM biopsy and blood counts are normal. 2,3 Unfortunately, the majority of AML patients (∼50%) will ultimately relapse 3,4 due to the persistent of some undetectable leukemic cells that will reinitiate the disease. This condition is named as minimal or, more appropriately, measurable residual disease (MRD).…”

“…5,6 In MRD conditions, the number of leukemic cells, called leukemic stem cells (LSCs), is down to 1 in 10 4 -10 6 total leukocytes, frequencies lower than routine measurement by morphology or cytogenetics are capable to detect. 3,7,8 Hence the isolation and detection of these blast cells remain one of the main challenges for MRD assessment in the clinic, highlighting the need of new techniques. In fact, next generation sequencing (NGS) has been used in some cases and has demonstrated high benefits in terms of diagnosis, prognosis, accurate risk stratification, and precision therapy in AML.…”