Critical evaluation of current molecular MRD strategies including NGS for the management of AML patients with multiple mutations

Measurable Residual Disease and Clonal Evolution in Acute Myeloid Leukemia from Diagnosis to Post-Transplant Follow-Up: The Role of Next-Generation Sequencing

It has now been ascertained that acute myeloid leukemias-as in most type of cancers-are mixtures of various subclones, evolving by acquiring additional somatic mutations over the course of the disease. The complexity of leukemia clone architecture and the phenotypic and/or genotypic drifts that can occur during treatment explain why more than 50% of patients-in hematological remission-could relapse. Moreover, the complexity and heterogeneity of clone architecture represent a hindrance for monitoring measurable residual disease, as not all minimal residual disease monitoring methods are able to detect genetic mutations arising during treatment. Unlike with chemotherapy, which imparts a relatively short duration of selective pressure on acute myeloid leukemia clonal architecture, the immunological effect related to allogeneic hematopoietic stem cell transplant is prolonged over time and must be overcome for relapse to occur. This means that not all molecular abnormalities detected after transplant always imply inevitable relapse. Therefore, transplant represents a critical setting where a measurable residual disease-based strategy, performed during post-transplant follow-up by highly sensitive methods such as next-generation sequencing, could optimize and improve treatment outcome. The purpose of our review is to provide an overview of the role of next-generation sequencing in monitoring both measurable residual disease and clonal evolution in acute myeloid leukemia patients during the entire course of the disease, with special focus on the transplant phase.

Feasibility and efficacy of salvage allogeneic stem cell transplantation in AML patients relapsing after autologous stem cell transplantation

Autologous hematopoietic cell transplantation (HCT) is suitable for consolidation of favorable-/intermediate-risk AML patients in CR1. However, ~50% of AML patients relapse after autologous HCT, and efficacy of subsequent salvage strategies including allogeneic HCT remains unclear. We studied 123 consecutive patients with newly diagnosed AML undergoing high-dose chemotherapy (HDCT)/autologous HCT in CR1. In relapsing patients afterwards, we analyzed salvage treatments and outcomes focusing particularly on salvage allogeneic HCT. Of 123 patients, 64 (52%) relapsed after autologous HCT. Subsequently, 13 (21%) received palliative therapy, whereas 51 (79%) proceeded to salvage therapy with a curative intent. Of the 47 patients with a curative intent and who did not proceed directly to allogeneic HCT, 23 (49%) achieved CR2 or had ongoing hematologic CR1 despite molecular relapse. Finally, 30 patients (47%) received allogeneic HCT with estimated 3-year leukemia-free and overall survival rates of 33% and 43%. Hematologic remission at allogeneic HCT and lack of acute GvHD had a positive impact on OS and LFS (p < 0.05). Our study suggests that almost 80% of AML patients can undergo salvage therapy following relapse after front-line HDCT/autologous HCT. Allogeneic HCT can provide cure in one third of patients relapsing after front-line HDCT/autologous HCT.

Comparison of flow cytometry and next-generation sequencing in minimal residual disease monitoring of acute myeloid leukemia: One institute's practical clinical experience

INTRODUCTION

Monitoring patients with acute myeloid leukemia can be implemented through various techniques such as multiparameter flow cytometry, real-time quantitative polymerase chain reaction, and next-generation sequencing. However, there is scarce studies when comparing the data of next-generation sequencing and flow cytometry for monitoring disease progression, particularly how they might supplement one another when used in tandem.

METHODS

We investigated 107 patients via retrospective analysis using follow-up MFC and NGS data with a total of 717 MFC and 247 NGS studies to compare these methods in monitoring minimal/measurable residual disease.

RESULTS

197 instances were MFC⁺ /NGS⁺ , 3 were MFC^- /NGS^- , 44 were MFC^- /NGS⁺ , and 3 are MFC⁺ /NGS^- . The majority of the MFC^- /NGS⁺ cases occurred within 6 months during the post-treatment phase (64%). Among 44 MFC^- /NGS⁺ instances, 13 had similar NGS profiles to their original day 0 diagnosis. The remaining cases showed preleukemic clonal hematopoiesis mutations, "likely pathogenic mutations," or "variants of uncertain significance."

CONCLUSION

Our findings show that flow cytometry has its advantages with comparable sensitivity in detecting minimal/measurable residual disease. Next-generation sequencing could be used in an increased and more regular capacity in conjunction with flow cytometry to achieve a more comprehensive surveillance of these patients, resulting in improved outcomes.

Clinical potential of introducing next-generation sequencing in patients at relapse of acute myeloid leukemia

Relapse of acute myeloid leukemia (AML) remains a major determinant of outcome. A number of molecularly directed treatment options have recently emerged making comprehensive diagnostics an important pillar of clinical decision making at relapse. Acknowledging the high degree of individual genetic variability at AML relapse, next-generation sequencing (NGS) has opened the opportunity for assessing the unique clonal hierarchy of individual AML patients. Knowledge on the genetic makeup of AML is reflected in patient customized treatment strategies thereby providing improved outcomes. For example, the emergence of druggable mutations at relapse enable the use of novel targeted therapies, including FLT3 inhibitors or the recently approved IDH1/2 inhibitors ivosidenib and enasidenib, respectively. Consequently, some patients may undergo novel bridging approaches for reinduction before allogeneic stem cell transplantation, or the identification of an adverse prognostic marker may initiate early donor search. In this review, we summarize the current knowledge of NGS in identifying clonal stability, clonal evolution, and clonal devolution in the context of AML relapse. In light of recent improvements in AML treatment options, NGS-based molecular diagnostics emerges as the basis for molecularly directed treatment decisions in patients at relapse.

Use of Minimal Residual Disease in Acute Myeloid Leukemia Therapy

OPINION STATEMENT

The expanding availability of minimal or more precisely measurable residual disease (MRD) assessment in acute myeloid leukemia (AML) with its possible implications for therapeutic decisions is of high interest to clinicians treating AML patients. A variety of mostly retrospective studies have shown that AML patients with a positive MRD test, assessed by different techniques at defined cutoffs and time-points, are at significantly higher risk of relapse and experience shorter overall survival compared to MRD-negative patients. How this valuable information may be adapted in the daily routine of patients' treatment to distinguish individuals who need more aggressive therapy from the ones who can be spared additional therapy to avoid treatment-related toxicities is still being investigated. With the exception of MRD analyses in acute promyelocitic leukemia (APL), the clinical implications of MRD tests for the individual AML patient are still mostly unknown. We currently lack hard evidence that MRD-based therapy modulation during treatment or pre-emptive intervention in MRD-positive patients after therapy would improve outcomes in non-APL AML patients. These questions will be evaluated in prospective randomized clinical trials. Today, however, some conclusions with regard to MRD assessment in AML can be drawn from the published data and are reviewed in this article.

Clinical Challenges and Consequences of Measurable Residual Disease in Non-APL Acute Myeloid Leukemia

The ability to detect residual levels of leukemic blasts (measurable residual disease, MRD) has already been integrated in the daily routine for treatment of patients with chronic myeloid and acute lymphoblastic leukemia. In acute myeloid leukemia (AML), a variety of mostly retrospective studies have shown that individuals in AML remission who tested positive for MRD at specific time-points or had increasing MRD levels are at significantly higher risk of relapse and death compared to MRD-negative patients. However, these studies differ with respect to the "MRD-target", time-point of MRD determination, material analyzed, and method applied. How this probably very valuable MRD information in individual patients may be adapted in the daily clinical routine, e.g., to separate patients who need more aggressive therapies from those who may be spared additional-potentially toxic-therapies is still a work-in-progress. With the exception of MRD assessment in acute promyelocytic leukemia (APL), the lack of randomized, prospective trials renders MRD-based decisions and clinical implications in AML a difficult task. As of today, we still do not have proof that early intervention in MRD-positive AML patients would improve outcomes, although this is very likely. In this article, we review the current knowledge on non-APL AML MRD assessment and possible clinical consequences.