Skip to Main Content

Advertisement intended for health care professionals

Skip Nav Destination

Making MRD Assessment Work for AML

August 21, 2023

September 2023

Advances in technology and research are bringing the goal of widespread assessment of MRD in AML closer.

Leah Lawrence

Leah Lawrence is a freelance health writer and editor based in Delaware.

Assessment of measurable residual disease (MRD) is more challenging and difficult to perform in acute myeloid leukemia (AML) than in chronic myeloid leukemia (CML) or acute lymphoblastic leukemia (ALL).

The concept of MRD is the evolution of how clinicians try to measure and understand responses to therapy, explained Christopher Hourigan, DM, DPhil, a senior investigator at the National Heart, Lung, and Blood Institute of the National Institutes of Health in Bethesda, Maryland.

“From the early days of leukemia management, you wanted to assess how well therapy was working … the sooner, the better,” said Dr. Hourigan, who focuses his research on the detection of AML MRD. “As far back as the 1950s, it was clear that the way we recorded responses needed to be harmonized. Using tools available at the time – signs and symptoms of leukemia, blood counts, and what could be seen under the microscope – the concept of complete remission [CR] was developed.”

The use of CR as a measurement of disease remained largely unchanged in acute leukemia until 2017. In its 2017 recommendations, the European LeukemiaNet (ELN) included a proposal for response categories based on MRD status, recognizing the possibility of submicroscopic levels of leukemia that remain even after CR. The new category was MRD-negative CR, and the proposal acknowledged that patients who are MRD negative have better outcomes than those who are not.1

In the treatment of other hematologic malignancies and leukemias, MRD testing has already been integrated into standards of care and response assessments, but that has been slower to happen in AML, even though MRD as a phenomenon has been known for decades.

ASH Clinical News spoke with Dr. Hourigan and other experts about the status of MRD assessment in AML, how it still lags behind other hematologic malignancies, and ongoing research being conducted to move things forward.

What’s the Difference?

In ALL, MRD has become an “essential prognostic tool” for all disease subtypes, as its detection is associated with worse disease-free survival (DFS) and overall survival (OS). Additionally, MRD status also affects treatment decisions in patients with ALL, although questions remain about its optimal timing.2 Measurement of MRD is much more straightforward in ALL compared with AML, in part because the majority of ALL is caused by somatic gene rearrangements, making multiparameter flow cytometry (MFC) more straightforward.3

“ALL can be defined clonally by rearrangement of immunoglobulin heavy chain gene locus or T-cell receptor genes,” said James S. Blachly, MD, associate professor of medicine at The Ohio State University James Comprehensive Cancer Center in Columbus. “Even if there are different mutations in ALL cells, they are all fundamentally derived from a clone with a specific genomic rearrangement. The same is not true of AML.”

Patients with AML may present with multiple immunophenotypic clones, any of which could contribute to MRD.

“In AML, there are a wide variety of clonal mutations that may need to be measured, and we don’t have good standardized genomic assays,” Dr. Blachly said. “The big difference between ALL and AML is we have to take one bite of the apple at a time in AML.”

Additionally, unlike in ALL, changes in antigen profiles occur with AML treatment, which can interfere with AML MRD detection.

Similar to ALL, MRD negativity in AML has also been associated with better DFS and OS. A meta-​analysis of data from 81 publications that included more than 11,000 patients showed an estimated five-​year DFS of 64% for patients with MRD negativity compared with 25% with MRD; estimated OS was 68% and 34%, respectively. These improved outcomes were consistent across MRD assessment timepoints, MRD specimen source, and AML subgroup.4

Measurement Methods

Several methods are used for monitoring AML MRD, but assays and reporting still lack standardization. The two main methods are MFC and molecular MRD testing using quantitative or digital polymerase chain reaction (PCR) or error-corrected next-​generation sequencing (NGS).

“The whole principle behind flow cytometry is looking for alterations in the expression of proteins, mainly on the cell surface, occasionally on the cytoplasm, that are different from normal populations of similar lineages and similar maturation stages,” said Brent Wood, MD, PhD, director of diagnostic immunology and flow cytometry at Children’s Hospital Los Angeles and professor of clinical pathology at Keck School of Medicine of the University of Southern California.

Using MFC to measure MRD is an extension of that, Dr. Wood said. It is looking for ever smaller populations of cells by creating assays that are more adapted to better distinguish normal cells from neoplastic cells at lower frequencies. The neoplastic cells nearly always express aberrant antigens or aberrant leukemia-​associated immunophenotypes.

MFC has several advantages for MRD testing, including its short turnaround time and relatively high sensitivity (10-3 to 10-5).5,6 However, the use of MFC is not well standardized and is limited by its subjective interpretation.

“Flow cytometry requires a kind of subjective interpretation by highly experienced individuals to look at the raw data and make determinations as to what is artifact, what is real … what is disease versus normal,” Dr. Wood said. “It is difficult to train and is difficult to scale.”

Dr. Wood noted that as more immunotherapies are incorporated into AML treatment, the use of MFC will also become more difficult.

“Many of the proteins that we are using for [MRD] measurements will be targeted by immunotherapy of various types,” Dr. Wood said. “That is certainly what is happening in ALL, and it is driving things more in the direction of molecular testing.”

When using the molecular methods, it is important to look at the right type of mutations and to understand how accurately they represent a state of residual disease that has a likelihood for generating relapse down the line, Dr. Wood said.

“Some mutations have been identified of that sort, such as NPM1 mutations,” Dr. Wood said. “These are one of the more common types of mutations that occur in adults and serve as a relatively reliable marker of residual disease linked to eventual outcome.”

However, a variety of other mutations that occur with aging results in clonal hematopoiesis, and these are not likely to be particularly useful for MRD monitoring.

In addition to distinguishing the predictive capability of any one mutation, another issue with AML MRD is that AML is a heterogeneous disease with many subsets and molecular mutations. Testing for any one mutation may be suitable for a subset of patients but not all patients.

With those limitations in mind, molecular-based techniques are more objective with fewer interpretative components, but they can be more technically challenging and costly.

Currently, the ELN recommends use of quantitative or digital PCR for patients with AML with mutant NPM1, RUNX1-RUNX1T1, or CBFB-MYH11 or those with acute promyelocytic leukemia. Outside of those subgroups, MRD should be tested using MFC.7

When To Test MRD

Data on how best to apply MRD assessment in the clinical management of AML are also needed. Potentially, the information could be used as a prognostic or predictive biomarker for risk assessment and treatment decisions, as a monitoring tool to identify relapse, and as a potential surrogate endpoint for clinical trials.7

Ideally, potential MRD markers should be identified at baseline.

“It helps to see the leukemia cells in a state where they are more numerous, usually prior to therapy,” Dr. Wood said. “That gives us some idea of what to look for after. Knowing what the starting point was points you in the right direction.”

The ELN then recommends MRD assessment on all bone marrow specimens obtained. For the approximately 60% of patients who will undergo MRD assessment using MFC, these assessments should occur after two cycles of chemotherapy, after consolidation, and before allogeneic hematopoietic cell transplantation. The timing of MRD assessment using molecular monitoring varies depending on the target being assessed; in most cases, MRD should be assessed in peripheral blood after two cycles of chemotherapy, in the bone marrow after consolidation, and then regularly for up to two years.7

However, Dr. Blachly said that, to his knowledge, clinicians have not widely adopted these guidelines.

“It is an aggressive schedule, and it will be interesting to see if U.S. payers will pay for it,” Dr. Blachly said. “That being said, I recommend a relatively aggressive schedule for testing MRD for specific patients.”

Utility of MRD

Dr. Hourigan noted it is no good discussing precision medicine techniques like MRD if the information gained doesn’t help patients.

“The hope is that with these tools we can give people better estimates of where they are during treatment and help them decide what is the next best step,” Dr. Hourigan said. The information should be used in therapeutic decision-making.

To begin to apply knowledge about MRD to patient management, Dr. Hourigan and colleagues conducted the observational Pre-MEASURE study. The study used targeted deep DNA sequencing from the blood of patients in first remission prior to transplant to test if the detection of certain residual AML-associated variants were linked with higher rates of post-transplant relapse and mortality. Using pretransplant blood samples from 1,075 patients, the study found that persistence of FLT3 internal tandem duplication or NPM1 variants were associated with increased relapse and worse survival compared with samples without these variants.8

“If we know that someone who goes into transplant with detectable MRD has a higher relapse probability, then we know that patient should participate in clinical trials of maintenance therapy,” Dr. Blachly said. “Knowing it is predictive of worse outcomes allows us to attempt interventions to help equalize those outcomes.”

The Pre-MEASURE study served as a proof of concept for the MEASURE study. Pre-MEASURE, Dr. Hourigan said, was limited by the information captured on baseline mutations. Currently recruiting, MEASURE is a prospective study designed to validate the idea of testing for MRD in patients undergoing transplant, but not just for patients with FLT3 ITD and NPM1.9

“To do that, we have to do something that is not typical in transplant protocols: collecting the original time-of-diagnosis material,” Dr. Hourigan said. “In MEASURE, we are asking for a banked sample from when the patient was first diagnosed to let us profile it and work out what the best markers are to track that patient’s MRD.”

The not-so-hidden agenda of this study, according to Dr. Hourigan, is to put together a network of high-​volume transplant centers all working toward the same goal.

“There is value in collaborations, and by setting up this network that is talking regularly, the hope is to build something where we go beyond developing the test and have clinical trials of interventions based on this platform,” Dr. Hourigan said.

In other words, as MRD measurement becomes more standardized, more research will be done to evaluate the use of MRD-directed therapies in AML.

The National Cancer Institute’s MyeloMATCH initiative is a planned four-tier umbrella study that will enroll patients with AML or myelodysplastic syndromes and test treatments against the current best standard of care. Among other things, MRD will be used as an efficacy endpoint, and the trials will help to facilitate the validation of MRD assays.10

Dr. Hourigan noted Sylvie Freeman, PhD, a colleague in MRD research, of the University of Birmingham in the U.K., has made the point that MRD tests for AML are not perfect, but neither are AML drugs, and the field continues to research and develop those.

“Let’s keep developing,” Dr. Hourigan encouraged, “rather than allowing ourselves to be paralyzed because there isn’t one perfect test.”

References

  1. Döhner H, Estry E, Grimwade D, et al. Diagnosis and management of AML in adults: 2017 ELN recommendations from an international expert panelBlood. 2017;129(4):424-447.
  2. Hein K, Short N, Jabbour E, Yilmaz M. Clinical value of measurable residual disease in acute lymphoblastic leukemia. Blood Lymphat Cancer. 2022;12:7-16.
  3. Paietta E. Minimal residual disease in AML: Why has it lagged behind pediatric ALL? Clin Lymphoma Myeloma Leuk. 2015;15 Suppl(0):S2-S6.
  4. Short NJ, Zhou S, Fu C, et al. Association of measurable residual disease with survival outcomes in patients with acute myeloid leukemia: a systematic review and meta-analysis. JAMA Oncol. 2020;6(12):1890-1899.
  5. Tettero JM, Freeman S, Buecklein V, et al. Technical aspects of flow cytometry-based measurable residual disease quantification in acute myeloid leukemia: experience of the European LeukemiaNet MRD Working Party. Hemasphere. 2022;6(1):e676.
  6. Döhner H, Wei AH, Appelbaum FR, et al. Diagnosis and management of AML in adults: 2022 recommendations from an international expert panel on behalf of the ELN. Blood. 2022;140(12):1345-1377.
  7. Heuser M, Freeman SD, Ossenkoppele GJ, et al. 2021 Update on MRD in acute myeloid leukemia: a consensus document from the European LeukemiaNet MRD Working Party. Blood. 2021;138(26):2753-2767.
  8. Dillon LW, Gui G, Page KM, et al. DNA sequencing to detect residual disease in adults with acute myeloid leukemia prior to hematopoietic cell transplant. JAMA. 2023;329(9):745-755.
  9. U.S. National Library of Medicine. ClinicalTrials.gov. Molecular evaluation of AML patients after stem cell transplant to understand relapse events (MEASURE). ClinicalTrials.gov Identifier: NCT05224661.
  10. U.S. National Library of Medicine. ClinicalTrials.gov. MyeloMATCH MSRP: a screening study to assign people with myeloid cancer to a treatment study. ClinicalTrials.gov Identifier: NCT05564390.

MRD Assessment Possible Tool for Personalized Treatment of MDS

Patients with myelodysplastic syndromes (MDS) are at risk for progression to acute myeloid leukemia (AML). Similar to AML, researchers and clinicians are still working to better define and understand the role of monitoring measurable residual disease (MRD) in patients with MDS.

“AML is often characterized by hot spot mutations, whereas MDS is characterized by point mutations seen at diagnosis that are analyzed using a next-generation sequencing (NGS) panel,” said Eva Hellström-Lindberg, MD, PhD, chair of the Department of Hematology at Karolinska University Hospital in Stockholm, Sweden.

However, the discovery of a universal MRD marker for MDS is unlikely given the heterogeneity of the disease, as is also the case with AML. This means individualized MRD monitoring may be the most effective strategy.

The only currently available curative treatment for MDS is allogeneic hematopoietic cell transplantation (alloHCT).

“In MDS, you never cure a patient with therapy alone, so the majority of research being done on MRD is after alloHCT,” Dr. Hellström-​Lindberg explained.

The NORDIC study was developed to evaluate if individual molecular MRD monitoring using digital droplet polymerase chain reaction (PCR) after alloHCT could predict clinical relapse earlier than conventional methods. Treating physicians were blinded to MRD results.

Results presented at the 2022 European Hematology Association Congress revealed that the researchers were able to develop a highly functional personalized MRD pipeline based on patient-specific mutations.1 Two-thirds of the patients on the study never had positive MRD, and Dr. Hellström-​Lindberg said the researchers were amazed to see this. Of the one-third of patients who were MRD positive, about half relapsed, indicating MRD positivity predicted relapse and relapse-free survival.

“This showed us that if a patient is persistently MRD negative, we can be a bit more light-handed in our approach, which would improve quality of life and also has a survival advantage,” Dr. Hellström-​Lindberg said.

The study also indicated that the use of digital droplet PCR was not difficult to perform. Ongoing research is exploring other techniques for measuring MRD in MDS, including AML-associated DNA methylation patterns and error-corrected NGS.2,3 A second NORDIC study has also been initiated to study the use of digital droplet PCR for MRD assessment in real time, giving the treating physician results within a week.

“This allows that doctor to apply the same techniques as they would today when you are suspicious that a patient may relapse,” Dr. Hellström-​Lindberg said. “We will study all these techniques and see in a couple of years what is best and most practical.”

References

  1. Tobiasson M, Pandzic T, Illman J, et al. Prediction of relapse after allogeneic stem cell transplantation using individualized measurable residual disease markers; the prospective NORDIC study NMDSG14B. Hemasphere. 2022;6:68-69.
  2. Božić T, Kuo C-C, Hapala J, et al. Investigation of measurable residual disease in acute myeloid leukemia by DNA methylation patterns. Leukemia. 2022;36(1):80-89.
  3. Thol F, Gabdouline R, Liebich A, et al. Measurable residual disease (MRD) monitoring by NGS before allogeneic hematopoietic cell transplantation in AML. Blood. 2018;132(16):1703-1713.

Advertisement intended for health care professionals

Connect with us:

CURRENT ISSUE
November 2024

Advertisement intended for health care professionals

Close Modal

or Create an Account

Close Modal
Close Modal

Advertisement intended for health care professionals