Measurable residual disease in acute lymphoblastic leukemia: methods and clinical context in adult patients

Novel prognostic factors and therapeutic advances in adult acute lymphoblastic leukemia

The prognosis of adult patients with acute lymphoblastic leukemia (ALL) has improved in the last decades. This has been due to the sum of several factors including more precise recognition of the ALL subtypes, refinement of the assessment of prognostic factors, improvement in pediatric-inspired chemotherapy regimens and especially to the incorporation of novel targeted and immune therapeutics, as well as engineered cellular therapies, among others. These therapies were initially developed for relapsed or refractory patients but are now being incorporated into frontline treatment and represent a major step forward in ALL therapy. This review focuses on the recent advances in ALL characterization and especially on the treatment of ALL in adults.

Indeterminate measurable residual disease by multiparameter flow cytometry is associated with an intermediate risk of clinical relapse in adult patients with acute leukaemia

Measurable residual disease (MRD) is useful for prognostication and for monitoring response to treatment in patients with acute leukaemia. MRD by multiparametric flow cytometry (MFC-MRD) utilises the leukaemia-associated immunophenotype (LAIP) and difference from normal (DfN) strategies to identify the leukaemic clone. Difficulties arise when the LAIP overlaps with normal regeneration, there is clonal evolution, or when the abnormal clone population is exceptionally small e.g., <0.01% of CD45+ cells. Such cases are reported as 'indeterminate'; however, there is little international consensus on this reporting. The relationship between clinical outcomes and indeterminate MFC-MRD is unknown. Here we determine the rate of indeterminate MFC-MRD reporting, its relationship to concurrent molecular MRD results when available, and to clinical outcomes to 12 months. We performed an internal audit of all adult testing for MFC-MRD between January and December 2021. A total of 153 consecutive patients with a diagnosis of acute leukaemia were included. Successive MFC-MRD results and clinical outcomes were recorded over a 12-month period from time of inclusion into the study. In total, 460 MFC-MRD tests from 153 patients were reviewed and 73 (16%) MFC-MRD tests from 54 (35%) patients were reported as indeterminate. The majority (70%) were at low levels between 0.01-0.1% of CD45+ cells. Compared to patients with a negative result, acute myeloid leukaemia (AML) was more frequent in patients who had an indeterminate MFC-MRD (70% vs 36%), and B-cell acute lymphoblastic leukaemia was less common (20% vs 55%). In patients with indeterminate MFC-MRD results, one-third had received either chemotherapy or allogeneic haemopoietic stem cell transplant (aHSCT) within the preceding 3 months. Agreement between MFC and molecular MRD testing was low. Patients with indeterminate MFC-MRD had leukaemia relapse rates below patients with a positive MFC-MRD, but greater than those with negative MFC-MRD (positive 33% vs indeterminate 21% vs negative 8%, p = 0.038). Overall, these findings indicate that indeterminate MFC-MRD results are more common in adults with AML and also in those who have received chemotherapy or aHSCT within the previous 3 months. We report for the first time that indeterminate MFC-MRD is a finding of potential clinical significance, which associates with a numerically higher median relapse rate within 12 months when compared to a negative MFC-MRD result.

Long-term outcome of 2-year survivors after allogeneic hematopoietic cell transplantation for acute leukemia

Information on late complications in patients with acute leukemia who have undergone allogeneic hematopoietic cell transplantation (HCT) is limited. We performed a left-truncated analysis of long-term survival in patients with acute leukemia who were alive and disease-free 2 years after HCT. We included 2701 patients with acute lymphoblastic leukemia (ALL) and 9027 patients with acute myeloid leukemia (AML) who underwent HCT between 2005 and 2012. The 10-year overall survival (OS) rate was 81.3% for ALL and 76.2% for AML, with the main causes of late mortality being relapse (ALL-33.9%, AML-44.9%) and chronic graft-versus-host disease (ALL-29%, AML-18%). At 10 years, HCT-related mortality was 16.8% and 20.4%, respectively. Older age and unrelated donor transplantation were associated with a worse prognosis for both types of leukemia. In addition, transplantation in the second or third complete remission and peripheral blood HSC for ALL are associated with worse outcomes. Similarly, adverse cytogenetics, female donor to male patient combination, and reduced intensity conditioning in AML contribute to poor prognosis. We conclude that 2-year survival in remission after HCT for acute leukemia is encouraging, with OS of nearly 80% at 10 years. However, the long-term mortality risk of HCT survivors remains significantly higher than that of the age-matched general population. These findings underscore the importance of tailoring transplantation strategies to improve long-term outcomes in patients with acute leukemia undergoing HCT.

Flow Cytometric Assessment of Malignant Hematologic Disorders

Multiparameter flow cytometry (MPF) is an essential component of the diagnostic workup of hematologic malignancies. Recently developed tools have expanded the utility of MPF in detecting T-cell clonality and myelomonocytic dysplasia. Minimal/measurable residual disease analysis has long been established as critical in the management of B-lymphoblastic leukemia and is emerging as a useful tool in myeloid malignancies. With the continued increased complexity of MPF assays, emerging tools for data collection and analysis will allow users to take full advantage of MPF in the diagnosis of hematologic disease.

Blinatumomab in the Therapy of Acute B-Lymphoid Leukemia

Blinatumomab, a CD19-CD3 bispecific T cell engager (BiTE), has two recombinant single-chain variable fragments that temporarily link CD3+ T cells and CD19+ B cells, leading to the T cell-mediated lysis of neoplastic B cells. Improved minimal residual disease (MRD)-negative response rates and long-term overall survival have been observed in B-ALL patients who received this drug. These therapeutic successes have led to FDA approval for refractory/relapsed and MRD-positive B-ALL patients. Furthermore, recent studies in newly diagnosed B-ALL patients have led in Philadelphia chromosome-positive patients to the development of chemotherapy-free regimens based on tyrosine kinase inhibitors plus Blinatumomab and in Philadelphia chromosome-negative patients to improvement in outcomes using chemotherapy regimens that have incorporated Blinatumomab in the consolidation phase of treatment.

MRD in Philadelphia Chromosome-Positive ALL: Methodologies and Clinical Implications

PURPOSE OF REVIEW

Measurable residual disease (MRD) is integral in the management of Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL). This review discusses the current methods used to evaluate MRD as well as the interpretation, significance, and incorporation of MRD in current practice.

RECENT FINDINGS

New molecular technologies have allowed the detection of MRD to levels as low as 10- 6. The most used techniques to evaluate MRD are multiparametric flow cytometry (MFC), quantitative reverse transcription polymerase chain reaction (RT-qPCR), and high-throughput next-generation sequencing (NGS). Each method varies in terms of advantages, disadvantages, and MRD sensitivity. MRD negativity after induction treatment and after allogeneic hematopoietic cell transplantation (HCT) is an important prognostic marker that has consistently been shown to be associated with improved outcomes. Blinatumomab, a new targeted therapy for Ph + ALL, demonstrates high efficacy in eradicating MRD and improving patient outcomes. In the relapsed/refractory setting, the use of inotuzumab ozogamicin and tisagenlecleucel has shown promise in eradicating MRD. The presence of MRD has become an important predictive measure in Ph + ALL. Current studies evaluate the use of MRD in treatment decisions, especially in expanding therapeutic options for Ph + ALL, including tyrosine kinase inhibitors, targeted antibody therapies, chimeric antigen receptor cell therapy, and HCT.

Clonotypic VDJ Rearrangements in Mixed Phenotype Acute Leukemia can be Successfully Utilized to Track Minimal Residual Disease

INTRODUCTION

Multiplex polymerase chain reaction (PCR) and next-generation sequencing (NGS) can both be used to identify a neoplastic clonotype by targeting CDR3 and assessing rearrangements in IgH, IgK, IgL, TCR-β, and TCR-gamma loci. The clonotypic sequence can be robustly used to track minimal residual disease (MRD). The ability to track MRD by NGS in mixed phenotype acute leukemia (MPAL) is unknown and warrants investigation.

METHODS

Institutional Review Board (IRB) approval was obtained. Central Moffitt Cancer Center (MCC) database was searched to locate any patients with MPAL from over 600,000 entries. Patient charts were manually curated to identify those with clonoSEQ data, and clinical data was procured from the electronic medical record (EMR).

RESULTS

Twenty-nine patients with MPAL were identified. Only 2 patients with clonoSEQ testing were found. Both demonstrated a B/myeloid phenotype, and both were bilineal. NGS (clonoSEQ) identified 4 dominant (IGH) (patient A; 8/2019) and 2 dominant sequences (patient B; 10/2019), respectively. In both patients, clonoSEQ testing successfully tracked minimal residual disease and mirrored clinical disease burden.

CONCLUSIONS

This report is the first to confirm the utility of NGS-based MRD tracking in patients with MPAL and shows increased sensitivity of NGS over MRD flow cytometry.

How I use next-generation sequencing-MRD to plan approach and prevent relapse after HCT for children and adults with ALL

ABSTRACT

Measurable residual disease (MRD) evaluation by multiparameter flow cytometry (MFC) or quantitative polymerase chain reaction methods is an established standard of care for assessing risk of relapse before or after hematopoietic cell transplantation (HCT) for acute lymphoblastic leukemia (ALL). Next-generation sequencing (NGS)-MRD has emerged as a highly effective approach that allows for the detection of lymphoblasts at a level of <1 in 106 nucleated cells, increasing sensitivity of ALL detection by 2 to 3 logs. Early studies have shown superior results compared with MFC and suggest that NGS-MRD may allow for the determination of patients in whom reduced toxicity transplant preparative approaches could be deployed without sacrificing outcomes. Many centers/study groups have implemented immune modulation approaches based on MRD measurements that have resulted in improved outcomes. Challenges remain with NGS-MRD, because it is not commercially available in many countries, and interpretation of results can be complex. Through patient case review, discussion of relevant studies, and detailed expert opinion, we share our approach to NGS-MRD testing before and after HCT in pediatric and adult ALL. Improved pre-HCT risk classification and post-HCT monitoring for relapse in bone marrow and less invasive peripheral blood monitoring by NGS-MRD may lead to alternative approaches to prevent relapse in patients undergoing this challenging procedure.

Laboratory validation and clinical utility of next-generation sequencing-based IGH/TCR clonality testing for the monitoring of measurable residual disease in acute lymphoblastic leukaemia: real-world experience at Austin Pathology

Measurable residual disease (MRD) testing is an essential aspect of disease prognostication in acute lymphoblastic leukaemia (ALL) and informs clinical decisions. The depth of MRD clearance is highly relevant and requires assays with sufficient sensitivity. Austin Pathology is one of the few laboratories in Australia currently utilising a fully validated and National Association of Testing Authorities (NATA)-accredited ultrasensitive next-generation sequencing (NGS) platform for MRD monitoring in ALL. This technology is based on the detection of clonal rearrangement of immunoglobulin and T cell receptor genes in leukaemic cells, and is capable of achieving a limit of detection at least one to two logs below that of multiparametric flow cytometry (MFC). In this retrospective analysis, we report a clonotype detection rate of up to 85.7% at diagnosis, and a concordance rate of 78.7% in MRD results between NGS and MFC. Of the discordant samples, nearly all were NGS+/MFC-, highlighting the superior sensitivity of NGS. The enhanced sensitivity is clinically relevant, as discordant MRD results often heralded fulminant relapse, and therefore offer clinicians additional lead time and a window of opportunity to initiate pre-emptive therapy. Notwithstanding a small and heterogeneous cohort, our real-world survival data indicate an intermediate relapse risk for NGS+/MFC- patients. In light of recent approval of Medicare rebatable ALL MRD testing, we discuss how NGS can complement other techniques such as MFC in personalising management strategies. We recommend routine clonality testing by NGS at diagnosis and use a multi-modality approach for subsequent MRD monitoring.

Acute Lymphoblastic Leukemia with Myeloid Mutations Is a High-Risk Disease Associated with Clonal Hematopoiesis

Myeloid neoplasms arise from preexisting clonal hematopoiesis (CH); however, the role of CH in the pathogenesis of acute lymphoblastic leukemia (ALL) is unknown. We found that 18% of adult ALL cases harbored TP53, and 16% had myeloid CH-associated gene mutations. ALL with myeloid mutations (MyM) had distinct genetic and clinical characteristics, associated with inferior survival. By using single-cell proteogenomic analysis, we demonstrated that myeloid mutations were present years before the diagnosis of ALL, and a subset of these clones expanded over time to manifest as dominant clones in ALL. Single-cell RNA sequencing revealed upregulation of genes associated with cell survival and resistance to apoptosis in B-ALL with MyM, which responds better to newer immunotherapeutic approaches. These findings define ALL with MyM as a high-risk disease that can arise from antecedent CH and offer new mechanistic insights to develop better therapeutic and preventative strategies.

SIGNIFICANCE

CH is a precursor lesion for lymphoblastic leukemogenesis. ALL with MyM has distinct genetic and clinical characteristics, associated with adverse survival outcomes after chemotherapy. CH can precede ALL years before diagnosis, and ALL with MyM is enriched with activated T cells that respond to immunotherapies such as blinatumomab. See related commentary by Iacobucci, p. 142.

Disparity in hematological malignancies: From patients to health care professionals

In the recent few decades, outcomes in patients diagnosed with hematological malignancies have been steadily improving. However, the improved prognosis does not distribute equally among patients from different backgrounds. Besides cancer biology, demographic and geographic disparities have been found to impact overall survival significantly. Specifically, patients from underrepresented minorities including Black and Hispanics, and those with uninsured status, having low socioeconomic status, or from rural areas have had worse outcomes historically, which is uniformly true across all major subtypes of hematological malignancies. Similar discrepancy is also seen in the health care professional field, where a gender gap and a disproportionally low representation of health care providers from underrepresented minorities have been long existing. Thus, a comprehensive strategy to mitigate disparity in the health care system is needed to achieve equity in health care.

Fmoc-FF hydrogels and nanogels for improved and selective delivery of dexamethasone in leukemic cells and diagnostic applications

Dexamethasone (DEX) is a synthetic analogue of cortisol commonly used for the treatment of different pathological conditions, comprising cancer, ocular disorders, and COVID-19 infection. Its clinical use is hampered by the low solubility and severe side effects due to its systemic administration. The capability of peptide-based nanosystems, like hydrogels (HGs) and nanogels (NGs), to serve as vehicles for the passive targeting of active pharmaceutical ingredients and the selective internalization into leukemic cells has here been demonstrated. Peptide based HGs loaded with DEX were formulated via the "solvent-switch" method, using Fmoc-FF homopeptide as building block. Due to the tight interaction of the drug with the peptidic matrix, a significant stiffening of the gel (G' = 67.9 kPa) was observed. The corresponding injectable NGs, obtained from the sub-micronization of the HG, in the presence of two stabilizing agents (SPAN®60 and TWEEN®60, 48/52 w/w), were found to be stable up to 90 days, with a mean diameter of 105 nm. NGs do not exhibit hemolytic effects on human serum, moreover they are selectively internalized by RS4;11 leukemic cells over healthy PBMCs, paving the way for the generation of new diagnostic strategies targeting onco-hematological diseases.

Long-term outcome after autologous BCR::ABL1-negative peripheral blood stem cell transplantation in adults with Philadelphia-positive acute lymphoblastic leukemia: a comparative study

Not available.

Clinical efficacy and safety of flumatinib versus dasatinib combined with multi-drug chemotherapy in adults with Philadelphia-positive acute lymphoblastic leukemia

INTRODUCTION

Flumatinib, a highly selective ABL kinase inhibitor, exhibits stronger inhibition of intracellular BCR-ABL tyrosine kinase activity, compared to Imatinib. However, there is limited research comparing the real-world efficacy and safety of flumatinib and dasatinib in patients with Philadelphia-positive acute lymphoblastic leukemia (Ph+ ALL).

OBJECTIVE

Investigating the differences in therapeutic efficacy and safety between flumatinib and dasatinib in combination with multi-drug chemotherapy for the treatment of newly diagnosed Ph+ ALL.

METHOD

In this study, we assessed 43 patients with newly diagnosed Ph+ ALL (20 in the flumatinib group, 23 in the dasatinib group).

RESULTS

There were no significant differences in gender, age, fusion gene type, initial blood routine, bone marrow blast cell ratio or chromosome karyotype between the two groups. Within 1 month, there were no significant differences in the complete response (CR), major molecular response (MMR) or minimal residual disease (MRD) negativity rate between the flumatinib and dasatinib groups. Similarly, within 3 months, there were no significant differences in CR or MMR rates between the two groups. However, the rates of complete molecular response (CMR) and MRD negativity within 3 months were significantly higher in the flumatinib group, compared to the dasatinib group (P < 0.05). Additionally, the flumatinib group exhibited fewer adverse reactions compared to the dasatinib group.

CONCLUSION

These findings suggest that flumatinib is a safe and effective tyrosine kinase inhibitor (TKI) for achieving CMR and MRD negativity in patients with Ph+ ALL, as supported by this small series of patients.

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

Minimal residual disease (MRD) is of major importance in onco-hematology, particularly in acute myeloid leukemia (AML). MRD measures the amount of leukemia cells remaining in a patient after treatment, and is an essential tool for disease monitoring, relapse prognosis, and guiding treatment decisions. Patients with a negative MRD tend to have superior disease-free and overall survival rates. Considerable effort has been made to standardize MRD practices. A variety of techniques, including flow cytometry and molecular methods, are used to assess MRD, each with distinct strengths and weaknesses. MRD is recognized not only as a predictive biomarker, but also as a prognostic tool and marker of treatment efficacy. Expected advances in MRD assessment encompass molecular techniques such as NGS and digital PCR, as well as optimization strategies such as unsupervised flow cytometry analysis and leukemic stem cell monitoring. At present, there is no perfect method for measuring MRD, and significant advances are expected in the future to fully integrate MRD assessment into the management of AML patients.

ZNF384 fusion transcript levels for measurable residual disease monitoring in adult B-cell acute lymphoblastic leukemia

Zinc finger protein 384 (ZNF384) rearrangement defined a novel subtype of B-cell acute lymphoblastic leukemia (B-ALL). The prognostic significance of ZNF384 fusion transcript levels represented measurable residual disease remains to be explored. ZNF384 fusions were screened out in 57 adult B-ALL patients at diagnosis by real-time quantitative polymerase chain reaction and their transcript levels were serially monitored during treatment. The reduction of ZNF384 fusion transcript levels at the time of achieving complete remission had no significant impact on survival, whereas its ≥2.5-log reduction were significantly associated with higher relapse free survival (RFS) and overall survival (OS) rates after course 1 consolidation (p = 0.022 and = 0.0083) and course 2 consolidation (p = 0.0025 and = 0.0008). Compared with chemotherapy alone, allogeneic hematopoietic stem cell transplantation (allo-HSCT) significantly improved RFS and OS of patients with <2.5-log reduction after course 1 consolidation (p < 0.0001 and = 0.0002) and course 2 consolidation (p = 0.0003 and = 0.019), whereas exerted no significant effects in patients with ≥2.5-log reduction (all p > 0.05). ZNF384 fusion transcript levels after course 1 and course 2 consolidation strongly predict relapse and survival and may guide whether receiving allo-HSCT in adult B-ALL.

Pediatric Hematopathology in the Era of Advanced Molecular Diagnostics: What We Know and How We Can Apply the Updated Classifications

Pediatric hematologic malignancies often show genetic features distinct from their adult counterparts, which reflect the differences in their pathogenesis. Advances in the molecular diagnostics including the widespread use of next-generation sequencing technology have revolutionized the diagnostic workup for hematologic disorders and led to the identification of new disease subgroups as well as prognostic information that impacts the clinical treatment. The increasing recognition of the importance of germline predisposition in various hematologic malignancies also shapes the disease models and management. Although germline predisposition variants can occur in patients with myelodysplastic syndrome/neoplasm (MDS) of all ages, the frequency is highest in the pediatric patient population. Therefore, evaluation for germline predisposition in the pediatric group can have significant clinical impact. This review discusses the recent advances in juvenile myelomonocytic leukemia, pediatric acute myeloid leukemia, B-lymphoblastic leukemia/lymphoma, and pediatric MDS. This review also includes a brief discussion of the updated classifications from the International Consensus Classification (ICC) and the 5th edition World Health Organization (WHO) classification regarding these disease entities.

Using Measurable Residual Disease to Optimize Management of AML, ALL, and Chronic Myeloid Leukemia

In this review, we discuss the use of measurable residual disease (MRD) in AML, ALL, and chronic myeloid leukemia (CML). Our aims were to review the different methodologies for MRD assessment; describe the clinical relevance and medical decision making on the basis of MRD; compare and contrast the usage of MRD across AML, ALL, and CML; and discuss what patients need to know about MRD as it relates to their disease status and treatment. Finally, we discuss ongoing challenges and future directions with the goal of optimizing MRD usage in leukemia management.

Challenges of detecting measurable/minimal disease in acute leukemia

Measurable/minimal residual disease (MRD) tracking has emerged as a powerful tool for assessing treatment response and predicting outcomes in acute leukemia. However, the clinical and technological challenges associated with MRD tracking must be addressed to improve its utility in routine patient care. This review article aims to provide a summary of the different MRD methodologies used in acute leukemia. It highlights the strengths, diagnostic pitfalls, and clinical utility associated with MRD tracking in this rapidly evolving field.

PH negative acute lymphoblastic leukemia in adolescents and young adults treated according a MRD adapted BFM ALL IC 2009 protocol: Argentine real-world data on 171 patients

Intensified pediatric chemotherapy regimens to treat adolescents and young adults (AYA) patients with Philadelphia negative acute lymphoblastic leukemia (ALL) have been associated with better outcomes. The local BFM 2009-based scheme complements the risk stratification assessing the measurable residual disease (MRD) along the induction phase with increasing levels of sensitivity. The present retrospective multicenter analysis included 171 AYA (15-40 years) patients treated accordingly between 2013 and 2019. Ninety-one percent obtained morphological complete remission, 67% a negative (<0.1%) MRD at day 33 (TP1), and 78% a negative (<0.01%) MRD at day 78 (TP2). The overall survival (OS) and the event-free survival (EFS) at 2 years were 62%±4.1 and 55%±4.1, respectively. The OS and EFS were significant better for prednisone responders, who achieved <10% BM blast at day 15, a negative MRD at TP1 or at TP2, and for low-risk patients. Age ≤30 years and WBC <30×10⁹/L, particularly among B-phenotype, were also associated with longer OS. In the multivariable analyses, TP1 MRD positive (OS HR 2.8, 95% CI 1.4-5.7, p=0.004; EFS HR 3.0, 95% CI 1.6-5.7, p=0.001) and at TP2 (OS HR 2.6, 95% CI 1.3-5.3, p=0.012; EFS HR 2.6, 95% CI 1.3-5.1, p=0.006) were independently associated with earlier events. Age >30 years was also associated with a shorter survival (HR 3.1, 95% CI 1.3-7.5, p=0.014). Therefore, those 68 patients ≤30 years with TP1/TP2 negative MRD depicted a longer OS (2 years 85%±4.8). Based on our real-world data, the pediatric-based scheme is feasible in Argentina associated with better outcomes for younger AYA patients who achieved negative MRD at day 33 and 78.