Minimal Residual Disease Assessment Improves Prediction of Outcome in Patients With Chronic Lymphocytic Leukemia (CLL) Who Achieve Partial Response: Comprehensive Analysis of Two Phase III Studies of the German CLL Study Group

End Point Surrogacy in First-Line Chronic Lymphocytic Leukemia

PURPOSE

Surrogate end points are commonly used to estimate treatment efficacy in clinical studies of chronic lymphocytic leukemia (CLL). This patient- and trial-level analysis describes the correlation between progression-free survival (PFS) and minimal residual disease (MRD) with overall survival (OS) in first-line trials for CLL.

PATIENTS AND METHODS

First, patient-level correlation was confirmed using source data from 12 frontline German CLL Study Group (GCLLSG)-trials. Additionally, a joint-frailty copula model was fitted to validate correlation in the setting of targeted therapies (TT). Second, a meta-analysis of first-line phase III trials in CLL from 2008 to 2024 was performed. Treatment effect correlation was quantified from seven GCLLSG and nine published trials, using hazard ratios (HRs) for time-to-event and odds ratios for binary end points.

RESULTS

The GCLLSG analysis set comprised 4,237 patients. Patient-level correlation for PFS/OS was strong with Spearman Rho >0.9. The joint-frailty copula indicated a weak correlation for chemotherapy/chemoimmunotherapy (C/CIT) with a tau of 0.52 (95% CI, 0.49 to 0.55) while the correlation was strong for TT (tau, 0.91 [95% CI, 0.89 to 0.93). The meta-analysis set contained a total of 8,065 patients including 5,198 (64%) patients treated with C/CIT and 2,867 (36%) treated with TT. Treatment-effect correlation of the HRs for PFS and OS was R = 0.75 (95% CI, 0.74 to 0.76, R2 = 0.56) while correlation of end-of-treatment MRD with PFS and OS was R = 0.88 (95% CI, -0.87 to 0.89; R2 = 0.78) and 0.71 (95% CI, 0.69 to 0.73; R2 = 0.5), respectively.

CONCLUSION

Patient-level correlation was confirmed in the setting of TTs while treatment-effect correlation between PFS and OS remains uncertain. MRD response status showed a high treatment-effect correlation with PFS but not OS, with the caveat of a limited number of randomized trials with available MRD data.

Measurable residual disease (MRD)-testing in haematological cancers: A giant leap forward or sideways?

Measurable residual disease (MRD)-testing is used in many haematological cancers to estimate relapse risk and to direct therapy. Sometimes MRD-test results are used for regulatory approval. However, some people including regulators wrongfully believe results of MRD-testing are highly accurate and of proven efficacy in directing therapy. We review MRD-testing technologies and evaluate the accuracy of MRD-testing for predicting relapse and the strength of evidence supporting efficacy of MRD-guided therapy. We show that at the individual level MRD-test results are often an inaccurate relapse predictor. Also, no convincing data indicate that increasing therapy-intensity based on a positive MRD-test reduces relapse risk or improves survival. We caution against adjusting therapy-intensity based solely on results of MRD-testing.

Predicting progression-free survival from measurable residual disease in chronic lymphocytic leukemia

Association between measurable residual disease (MRD) and survival outcomes in chronic lymphocytic leukemia (CLL) has often been reported. However, limited quantitative analyses over large datasets have been undertaken to establish the predictive power of MRD. Here, we provide a comprehensive assessment of published MRD data to explore the utility of MRD in the prediction of progression-free survival (PFS). We undertook two independent analyses, which leveraged available published data to address two complimentary questions. In the first, data from eight clinical trials was modeled via a meta-regression approach, showing that median PFS can be predicted from undetectable MRD rates at 3-6 months of post-treatment. The resulting model can be used to predict the probability of technical success of a planned clinical trial in chemotherapy. In the second, we investigated the evidence for predicting PFS from competing MRD metrics, for example baseline value and instantaneous MRD value, via a joint modeling approach. Using data from four small studies, we found strong evidence that including MRD metrics in joint models improves predictions of PFS compared with not including them. This analysis suggests that incorporating MRD is likely to better inform individual progression predictions. It is therefore proposed that systematic MRD collection should be accompanied by modeling to generate algorithms that inform patients' progression.

What clinicians should know about surrogate end points in hematologic malignancies

ABSTRACT

Use of surrogates as primary end points is commonplace in hematology/oncology clinical trials. As opposed to prognostic markers, surrogates are end points that can be measured early and yet can still capture the full effect of treatment, because it would be captured by the true outcome (eg, overall survival). We discuss the level of evidence of the most commonly used end points in hematology and share recommendations on how to apply and evaluate surrogate end points in research and clinical practice. Based on the statistical literature, this clinician-friendly review intends to build a bridge between clinicians and surrogacy specialists.

Realizing precision medicine in chronic lymphocytic leukemia: Remaining challenges and potential opportunities

Patients with chronic lymphocytic leukemia (CLL) exhibit diverse clinical outcomes. An expanding array of genetic tests is now employed to facilitate the identification of patients with high-risk disease and inform treatment decisions. These tests encompass molecular cytogenetic analysis, focusing on recurrent chromosomal alterations, particularly del(17p). Additionally, sequencing is utilized to identify TP53 mutations and to determine the somatic hypermutation status of the immunoglobulin heavy variable gene. Concurrently, a swift advancement of targeted treatment has led to the implementation of novel strategies for patients with CLL, including kinase and BCL2 inhibitors. This review explores both current and emerging diagnostic tests aimed at identifying high-risk patients who should benefit from targeted therapies. We outline existing treatment paradigms, emphasizing the importance of matching the right treatment to the right patient beyond genetic stratification, considering the crucial balance between safety and efficacy. We also take into consideration the practical and logistical issues when choosing a management strategy for each individual patient. Furthermore, we delve into the mechanisms underlying therapy resistance and stress the relevance of monitoring measurable residual disease to guide treatment decisions. Finally, we underscore the necessity of aggregating real-world data, adopting a global perspective, and ensuring patient engagement. Taken together, we argue that precision medicine is not the mere application of precision diagnostics and accessibility of precision therapies in CLL but encompasses various aspects of the patient journey (e.g., lifestyle exposures and comorbidities) and their preferences toward achieving true personalized medicine for patients with CLL.

Monitoring Response and Resistance to Treatment in Chronic Lymphocytic Leukemia

The recent evolution in chronic lymphocytic leukemia (CLL) targeted therapies led to a progressive change in the way clinicians manage the goals of treatment and evaluate the response to treatment in respect to the paradigm of the chemoimmunotherapy era. Continuous therapies with BTK inhibitors achieve prolonged and sustained control of the disease. On the other hand, venetoclax and anti-CD20 monoclonal antibodies or, more recently, ibrutinib plus venetoclax combinations, given for a fixed duration, achieve undetectable measurable residual disease (uMRD) in the vast majority of patients. On these grounds, a time-limited MRD-driven strategy, a previously unexplored scenario in CLL, is being attempted. On the other side of the spectrum, novel genetic and non-genetic mechanisms of resistance to targeted treatments are emerging. Here we review the response assessment criteria, the evolution and clinical application of MRD analysis and the mechanisms of resistance according to the novel treatment strategies within clinical trials. The extent to which this novel evidence will translate in the real-life management of CLL patients remains an open issue to be addressed.

Bridging horizons beyond CIRCULATE-Japan: a new paradigm in molecular residual disease detection via whole genome sequencing-based circulating tumor DNA assay

Circulating tumor DNA (ctDNA) is the fraction of cell-free DNA in patient blood that originates from a tumor. Advances in DNA sequencing technologies and our understanding of the molecular biology of tumors have increased interest in exploiting ctDNA to facilitate detection of molecular residual disease (MRD). Analysis of ctDNA as a promising MRD biomarker of solid malignancies has a central role in precision medicine initiatives exemplified by our CIRCULATE-Japan project involving patients with resectable colorectal cancer. Notably, the project underscores the prognostic significance of the ctDNA status at 4 weeks post-surgery and its correlation to adjuvant therapy efficacy at interim analysis. This substantiates the hypothesis that MRD is a critical prognostic indicator of relapse in patients with colorectal cancer. Despite remarkable advancements, challenges endure, primarily attributable to the exceedingly low ctDNA concentration in peripheral blood, particularly in scenarios involving low tumor shedding and the intrinsic error rates of current sequencing technologies. These complications necessitate more sensitive and sophisticated assays to verify the clinical utility of MRD across all solid tumors. Whole genome sequencing (WGS)-based tumor-informed MRD assays have recently demonstrated the ability to detect ctDNA in the parts-per-million range. This review delineates the current landscape of MRD assays, highlighting WGS-based approaches as the forefront technique in ctDNA analysis. Additionally, it introduces our upcoming endeavor, WGS-based pan-cancer MRD detection via ctDNA, in our forthcoming project, SCRUM-Japan MONSTAR-SCREEN-3.

Predictive and prognostic molecular biomarkers in lymphomas

Recent advances in molecular diagnostics have markedly expanded our understanding of the genetic underpinnings of lymphomas and catalysed a transformation in not just how we classify lymphomas, but also how we treat, target, and monitor affected patients. Reflecting these advances, the World Health Organization Classification, International Consensus Classification, and National Comprehensive Cancer Network guidelines were recently updated to better integrate these molecular insights into clinical practice. We summarise here the molecular biomarkers of lymphomas with an emphasis on biomarkers that have well-supported prognostic and predictive utility, as well as emerging biomarkers that show promise for clinical practice. These biomarkers include: (1) diagnostic entity-defining genetic abnormalities [e.g., B-cell acute lymphoblastic leukaemia (B-ALL) with KMT2A rearrangement]; (2) molecular alterations that guide patients' prognoses (e.g., TP53 loss frequently conferring worse prognosis); (3) mutations that serve as the targets of, and often a source of acquired resistance to, small molecular inhibitors (e.g., ABL1 tyrosine kinase inhibitors for B-ALL BCR::ABL1, hindered by ABL1 kinase domain resistance mutations); (4) the growing incorporation of molecular measurable residual disease (MRD) in the management of lymphoma patients (e.g., molecular complete response and sequencing MRD-negative criteria in multiple myeloma). Altogether, our review spans the spectrum of lymphoma types, from the genetically defined subclasses of precursor B-cell lymphomas to the highly heterogeneous categories of small and large cell mature B-cell lymphomas, Hodgkin lymphomas, plasma cell neoplasms, and T/NK-cell lymphomas, and provides an expansive summary of our current understanding of their molecular pathology.

Chronic Lymphocytic Leukemia: Time-Limited Therapy in the First-Line Setting and Role of Minimal Residual Disease

PURPOSE OF REVIEW

In this review, we provide an overview of different time-limited combination therapies of chronic lymphocytic leukemia (CLL) and summarize the data of pivotal clinical studies. Furthermore, we discuss the relevance of MRD in clinical trials and summarize the challenges that arise in routine clinical care. Finally, we provide an outlook on studies and datasets needed to optimize the use of time-limited treatment strategies and MRD assessments in modern CLL management.

RECENT FINDINGS

In recent years, first-line treatment of CLL has undergone a considerable transformation, with targeted substances having largely replaced chemoimmunotherapy (CIT) as a time-limited strategy in the frontline setting. BTK inhibitors were the first class of targeted agents introduced in CLL, which achieved longer progression-free survival (PFS) and in some cases also overall survival (OS) than CIT. However, this required an indefinite drug intake until disease progression, while CIT is generally administered over the course of few months. In contrast to BTK inhibitors, BCL2 inhibitors, another class of targeted agents, can achieve high rates of undetectable minimal residual disease (uMRD) levels and induce deep molecular remissions with the potential to stop treatment while maintaining remissions. Combinations of BCL2 inhibitors with CD20 antibodies or with BTK inhibitors have been explored to establish time-limited treatment strategies with targeted agents. In this context, one of the strongest predictors of long-term outcomes is MRD status at the end of treatment, which has been shown to correlate closely with PFS and OS in most cases.

Evidence-Based Management of Chronic Lymphocytic Leukemia: Consensus Statements from the Gulf Region

INTRODUCTION

Despite recent advances in diagnosis, prognostication, and treatment options, chronic lymphocytic leukemia (CLL) is still a largely incurable disease. New concepts on diagnosis, staging, treatment, and follow-up on CLL have been incorporated throughout recent years. The lack of regional consensus guidelines has led to varying practices in the management of patients with CLL in the region. This manuscript aims to reach a consensus among expert hematologists regarding the definitions, classifications, and related practices of CLL. The experts developed a set of statements utilizing their personal experience together with the current literature on CLL management. This consensus aims to provide guidance for healthcare professionals involved in the management of CLL and serves as a step in developing regional guidelines.

METHODS

Eight experts responded to 50 statements regarding the diagnosis, staging, treatment, and prognosis of CLL with three potential answering alternatives ranging between agree, disagree, and abstain. This consensus adopted a modified Delphi consensus methodology. A consensus was reached when at least 75% of the agreement to the answer was reached. This manuscript presents the scientific insights of the participating attendees, panel discussions, and the supporting literature review.

RESULTS

Of the 50 statements, a consensus was reached on almost all statements. Statements covered CLL-related topics, including diagnostic evaluation, staging, risk assessment, different patient profiles, prognostic evaluation, treatment decisions, therapy sequences, response evaluation, complications, and CLL during the COVID-19 pandemic.

CONCLUSION

In recent years, CLL management has progressed significantly, with many diagnostic tests and several novel treatments becoming available. This consensus gathers decades of consolidated principles, novel research, and promising prospects for the management of this disease.

Chronic lymphocytic leukaemia Australasian consensus practice statement

Chronic lymphocytic leukaemia (CLL) is the most common haematological malignancy in Australia and New Zealand (ANZ). Considerable changes to diagnostic and management algorithms have occurred within the last decade. The availability of next-generation sequencing and measurable residual disease assessment by flow cytometry allow for advanced prognostication and response assessments. Novel therapies, including inhibitors of Bruton's tyrosine kinase (BTKi) and B-cell lymphoma 2 (BCL2) inhibitors, have transformed the treatment landscape for both treatment-naïve and relapsed/refractory disease, particularly for patients with high-risk genetic aberrations. Recommendations regarding appropriate supportive management continue to evolve, and special considerations are required for patients with CLL with respect to the global SARS-CoV-2 pandemic. The unique funding and treatment environments in Australasia highlight the need for specific local guidance with respect to the investigation and management of CLL. This consensus practice statement was developed by a broadly representative group of ANZ experts in CLL with endorsement by peak haematology bodies, with a view to providing this standardised guidance.

Minimal Residual Disease Data in Hematologic Malignancy Drug Applications and Labeling: An FDA Perspective

Minimal residual disease (MRD) is increasingly used as a prognostic biomarker, a measure of clinical efficacy, and a guide for treatment decisions in various hematologic malignancies. We sought to characterize MRD data in registrational trials in hematologic malignancies submitted to the U.S. Food and Drug Administration (FDA) with the ultimate goal of expanding the utility of MRD data in future drug applications. We descriptively analyzed MRD data collected in registrational trials, including the type of MRD endpoint, assay, disease compartment(s) assessed, and the acceptance of MRD data in the U.S. prescribing information (USPI). Of 196 drug applications submitted between January 2014 and February 2021, 55 (28%) included MRD data. Of the 55 applications, MRD data was proposed by the Applicant for inclusion in the USPI in 41 (75%) applications but was included in only 24 (59%). Despite an increasing number of applications that proposed to include MRD data in the USPI, the acceptance rate decreased over time. Although MRD data have the potential to expedite drug development, our analysis identified challenges and specific areas for improvement, including assay validation, standardization of collection methods to optimize performance, and considerations in trial design and statistical methodology.

Computational flow cytometry provides accurate assessment of measurable residual disease in chronic lymphocytic leukaemia

Undetectable measurable residual disease (MRD) is associated with favourable clinical outcomes in chronic lymphocytic leukaemia (CLL). While assessment is commonly performed using multiparameter flow cytometry (MFC), this approach is associated with limitations including user bias and expertise that may not be widely available. Implementation of unsupervised clustering algorithms in the laboratory can address these limitations and have not been previously reported in a systematic quantitative manner. We developed a computational pipeline to assess CLL MRD using FlowSOM. In the training step, a self-organising map was generated with nodes representing the full breadth of normal immature and mature B cells along with disease immunophenotypes. This map was used to detect MRD in multiple validation cohorts containing a total of 456 samples. This included an evaluation of atypical CLL cases and samples collected from two different laboratories. Computational MRD showed high correlation with expert analysis (Pearson's r > 0.99 for typical CLL). Binary classification of typical CLL samples as either MRD positive or negative demonstrated high concordance (>98%). Interestingly, computational MRD detected disease in a small number of atypical CLL cases in which MRD was not detected by expert analysis. These results demonstrate the feasibility and value of automated MFC analysis in a diagnostic laboratory.

Impact of Minimal Residual Disease on Progression-Free Survival Outcomes After Fixed-Duration Ibrutinib-Venetoclax Versus Chlorambucil-Obinutuzumab in the GLOW Study

PURPOSE

In GLOW, fixed-duration ibrutinib + venetoclax showed superior progression-free survival (PFS) versus chlorambucil + obinutuzumab in older/comorbid patients with previously untreated chronic lymphocytic leukemia (CLL). The current analysis describes minimal residual disease (MRD) kinetics and any potential predictive value for PFS, as it has not yet been evaluated for ibrutinib + venetoclax treatment.

METHODS

Undetectable MRD (uMRD) was assessed by next-generation sequencing at <1 CLL cell per 10,000 (<10^-4) and <1 CLL cell per 100,000 (<10^-5) leukocytes. PFS was analyzed by MRD status at 3 months after treatment (EOT+3).

RESULTS

Ibrutinib + venetoclax achieved deeper uMRD (<10^-5) rates in bone marrow (BM) and peripheral blood (PB), respectively, in 40.6% and 43.4% of patients at EOT+3 versus 7.6% and 18.1% of patients receiving chlorambucil + obinutuzumab. Of these patients, uMRD (<10^-5) in PB was sustained during the first year post-treatment (EOT+12) in 80.4% of patients receiving ibrutinib + venetoclax and 26.3% receiving chlorambucil + obinutuzumab. Patients with detectable MRD (dMRD; ≥10^-4) in PB at EOT+3 were more likely to sustain MRD levels through EOT+12 with ibrutinib + venetoclax versus chlorambucil + obinutuzumab. PFS rates at EOT+12 were high among patients treated with ibrutinib + venetoclax regardless of MRD status at EOT+3: 96.3% and 93.3% in patients with uMRD (<10^-4) and dMRD (≥10^-4) in BM, respectively, versus 83.3% and 58.7% for patients receiving chlorambucil + obinutuzumab. PFS rates at EOT+12 also remained high in patients with unmutated immunoglobulin heavy-chain variable region (IGHV) receiving ibrutinib + venetoclax, independent of MRD status in BM.

CONCLUSION

Molecular and clinical relapses were less frequent during the first year post-treatment with ibrutinib + venetoclax versus chlorambucil + obinutuzumab regardless of MRD status at EOT+3 and IGHV status. Even for patients not achieving uMRD (<10^-4), PFS rates remained high with ibrutinib + venetoclax; this is a novel finding and requires additional follow-up to confirm its persistence over time.

Measurable Residual Disease in Chronic Lymphocytic Leukemia: Current Understanding and Evolving Role in Clinical Practice

OPINION STATEMENT

Treatment of chronic lymphocytic leukemia (CLL) has evolved dramatically during the last decade, from chemoimmunotherapy (CIT)-based therapies to newer B-cell receptor (BCR) signaling targeting agents, which are sometimes given as continuous schemes. Response to treatment was traditionally defined according to clinical variables designed to assign a response category. Interest in assessing for deeper responses in CLL by the means of measurable residual disease (MRD) testing has been the subject of research during the last several years. Analyses and sub-analyses of clinical trials have shown that achieving undetectable MRD (uMRD) in CLL is an important prognostic factor. In this review, we summarize the available evidence about MRD in CLL, from the various assays available for measurement, the compartment to test, the impact of reaching uMRD according to the treatment regimen, and the results of fixed duration treatment guided by MRD trials. Finally, we summarize how MRD can be incorporated in clinical practice and how it may guide fixed duration treatment in the future should evidence continue to accumulate in that direction.

Transcriptomic profiles and 5-year results from the randomized CLL14 study of venetoclax plus obinutuzumab versus chlorambucil plus obinutuzumab in chronic lymphocytic leukemia

Data on long-term outcomes and biological drivers associated with depth of remission after BCL2 inhibition by venetoclax in the treatment of chronic lymphocytic leukemia (CLL) are limited. In this open-label parallel-group phase-3 study, 432 patients with previously untreated CLL were randomized (1:1) to receive either 1-year venetoclax-obinutuzumab (Ven-Obi, 216 patients) or chlorambucil-Obi (Clb-Obi, 216 patients) therapy (NCT02242942). The primary endpoint was investigator-assessed progression-free survival (PFS); secondary endpoints included minimal residual disease (MRD) and overall survival. RNA sequencing of CD19-enriched blood was conducted for exploratory post-hoc analyses. After a median follow-up of 65.4 months, PFS is significantly superior for Ven-Obi compared to Clb-Obi (Hazard ratio [HR] 0.35 [95% CI 0.26-0.46], p < 0.0001). At 5 years after randomization, the estimated PFS rate is 62.6% after Ven-Obi and 27.0% after Clb-Obi. In both arms, MRD status at the end of therapy is associated with longer PFS. MRD + ( ≥ 10-4) status is associated with increased expression of multi-drug resistance gene ABCB1 (MDR1), whereas MRD6 (< 10-6) is associated with BCL2L11 (BIM) expression. Inflammatory response pathways are enriched in MRD+ patient solely in the Ven-Obi arm. These data indicate sustained long-term efficacy of fixed-duration Ven-Obi in patients with previously untreated CLL. The distinct transcriptomic profile of MRD+ status suggests possible biological vulnerabilities.

Integrated analysis of next generation sequencing minimal residual disease (MRD) and PET scan in transplant eligible myeloma patients

Minimal residual disease (MRD) assays allow response assessment in patients with multiple myeloma (MM), and negativity is associated with improved survival outcomes. The role of highly sensitive next generation sequencing (NGS) MRD in combination with functional imaging remains to be validated. We performed a retrospective analysis on MM patients who underwent frontline autologous stem cell transplant (ASCT). Patients were evaluated at day 100 post-ASCT with NGS-MRD and positron emission tomography (PET-CT). Patients with ≥ 2 MRD measurements were included in a secondary analysis for sequential measurements. 186 patients were included. At day 100, 45 (24.2%) patients achieved MRD negativity at a sensitivity threshold of 10-6. MRD negativity was the most predictive factor for longer time to next treatment (TTNT). Negativity rates did not differ according to MM subtype, R-ISS Stage nor cytogenetic risk. PET-CT and MRD had poor agreement, with high rates of PET-CT negativity in MRD-positive patients. Patients with sustained MRD negativity had longer TTNT, regardless of baseline risk characteristics. Our results show that the ability to measure deeper and sustainable responses distinguishes patients with better outcomes. Achieving MRD negativity was the strongest prognostic marker and could help guide therapy-related decisions and serve as a response marker for clinical trials.

Emerging Therapies in CLL in the Era of Precision Medicine

Over the past decade, the treatment landscape of CLL has vastly changed from the conventional FC (fludarabine and cyclophosphamide) and FCR (FC with rituximab) chemotherapies to targeted therapies, including inhibitors of Bruton tyrosine kinase (BTK) and phosphatidylinositol 3-kinase (PI3K) as well as inhibitors of BCL2. These treatment options dramatically improved clinical outcomes; however, not all patients respond well to these therapies, especially high-risk patients. Clinical trials of immune checkpoint inhibitors (PD-1, CTLA4) and chimeric antigen receptor T (CAR T) or NK (CAR NK) cell treatment have shown some efficacy; still, long-term outcomes and safety issues have yet to be determined. CLL remains an incurable disease. Thus, there are unmet needs to discover new molecular pathways with targeted or combination therapies to cure the disease. Large-scale genome-wide whole-exome and whole-genome sequencing studies have discovered genetic alterations associated with disease progression, refined the prognostic markers in CLL, identified mutations underlying drug resistance, and pointed out critical targets to treat the disease. More recently, transcriptome and proteome landscape characterization further stratified the disease and revealed novel therapeutic targets in CLL. In this review, we briefly summarize the past and present available single or combination therapies, focusing on potential emerging therapies to address the unmet clinical needs in CLL.

Current Landscape of Ancillary Diagnostic Testing in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is the most common adult leukemia and is a heterogeneous disease with variable patient outcomes. A multidisciplinary technical evaluation, including flow cytometry, immunohistochemistry, molecular and cytogenetic analyses, can comprehensively characterize a patient's leukemia at diagnosis, identify important prognostic biomarkers, and track measurable residual disease; all of which can impact patient management. This review highlights the key concepts, clinical significance, and main biomarkers detectable with each of these technical approaches; the contents are a helpful resource for medical practitioners involved in the workup and management of patients with CLL.

The evolving use of measurable residual disease in chronic lymphocytic leukemia clinical trials

Measurable residual disease (MRD) status in chronic lymphocytic leukemia (CLL), assessed on and after treatment, correlates with increased progression-free and overall survival benefit. More recently, MRD assessment has been included in large clinical trials as a primary outcome and is increasingly used in routine practice as a prognostic tool, a therapeutic goal, and potentially a trigger for early intervention. Modern therapy for CLL delivers prolonged remissions, causing readout of traditional trial outcomes such as progression-free and overall survival to be inherently delayed. This represents a barrier for the rapid incorporation of novel drugs to the overall therapeutic armamentarium. MRD offers a dynamic and robust platform for the assessment of treatment efficacy in CLL, complementing traditional outcome measures and accelerating access to novel drugs. Here, we provide a comprehensive review of recent major clinical trials of CLL therapy, focusing on small-molecule inhibitors and monoclonal antibody combinations that have recently emerged as the standard frontline and relapse treatment options. We explore the assessment and reporting of MRD (including novel techniques) and the challenges of standardization and provide a comprehensive review of the relevance and adequacy of MRD as a clinical trial endpoint. We further discuss the impact that MRD data have on clinical decision-making and how it can influence a patient's experience. Finally, we evaluate how upcoming trial design and clinical practice are evolving in the face of MRD-driven outcomes.

Flow cytometric evaluation of measurable residual disease in chronic lymphocytic leukemia: Where do we stand?

Measurable residual disease (MRD) has emerged as a relevant parameter of response to therapy in chronic lymphocytic leukemia (CLL). Although several methods have been developed, flow cytometry has emerged as the most useful and standardized approach to measure and quantify MRD. The improved sensitivity of MRD measurements has been paralleled by the development of more effective therapeutic strategies for CLL, increasing the applicability of MRD detection in this setting. Chemotherapy and chemoimmunotherapy have firstly demonstrated their ability to obtain a deep MRD. Combined targeted therapies are also demonstrating a high molecular response rate and prospective trials are exploring the role of MRD to guide the duration of treatment in this setting. In this review we briefly summarize what we have learned about MRD with emphasis on its flow cytometric detection.

Utility of measurable residual disease for predicting treatment outcomes with BCR- and BCL2-Targeted therapies in patients with CLL

Inhibitors targeting B-cell receptor (BCR) signaling pathway proteins and B-cell lymphoma-2 (BCL2) in chronic lymphocytic leukemia (CLL) are recommended in the first-line and relapsed/refractory disease settings. Measurable residual disease (MRD) is an important prognostic tool in patients treated with the BCL2-targeted agent, venetoclax. We explored the relationship between MRD status and progression-free (PFS)/overall survival (OS) in patients with CLL, following treatment with novel BCR- and BCL2-targeted agents. Compared with chemoimmunotherapy, higher rates of undetectable (u)MRD were achieved with BCL2-targeted therapies; achieving uMRD status was associated with longer PFS and OS than MRD-positivity. Continuous treatment with BCR-targeted agents did not achieve uMRD status in many patients, and outcomes were not correlated with uMRD status. Future clinical trials of targeted treatment combinations could be designed to demonstrate uMRD as a treatment objective, and allow a response-driven, personalized strategy to optimize treatment and improve OS outcomes.

Circulating Tumor DNA-Based MRD Assessment in Patients with CLL Treated with Obinutuzumab, Acalabrutinib, and Venetoclax

PURPOSE

With the advent of highly efficacious time-limited combination treatments of targeted agents in chronic lymphocytic leukemia (CLL), minimal residual disease (MRD) assessment has gained importance as a measure for therapeutic success and as a surrogate for progression-free survival. The currently most widely used method is multicolor flow cytometry, which detects circulating CLL cells in the peripheral blood. However, it seems to be less sensitive for the detection of MRD in the lymph node compartment.

PATIENTS AND METHODS

To evaluate whether a cell-free approach can overcome this limitation, we performed serial assessments of circulating tumor DNA (ctDNA) in patients with CLL treated with obinutuzumab, acalabrutinib, and venetoclax in the phase II CLL2-BAAG trial. Patient-specific variability, diversity, joining (VDJ) rearrangements as well as somatic driver mutations were tracked before, during and after treatment by digital droplet PCR in blood plasma. Furthermore, these were systematically compared to matched flow cytometry data.

RESULTS

In the 381 sample pairs, ctDNA and flow cytometry yielded highly concordant results. However, clone-specific ctDNA was detected in 44 of 152 samples (29%) that were assessed as undetectable MRD (uMRD) by flow cytometry (defined as less than one CLL cell in 10,000 normal leukocytes). 29 ctDNA-negative samples showed detectable MRD >10-4 by flow cytometry. Also, somatic driver mutations were detected with a similar sensitivity compared with patient-specific VDJ rearrangements in plasma. In patients with predominantly nodal residual disease, ctDNA compared favorably with 4-color flow cytometry and seemed to more accurately reflect the entire disease burden across compartments.

CONCLUSIONS

On the basis of these findings, ctDNA-based MRD assessment appears to be a promising method to complement cell-based MRD approaches like flow cytometry that focus on circulating CLL cells in the peripheral blood.

Real-world management of targeted therapies in chronic lymphocytic leukemia

The advent of novel targeted therapies, including B-cell receptor (BCR) pathway and B-cell lymphoma 2 (BCL2) inhibitors, has substantially changed the treatment paradigm for chronic lymphocytic leukemia (CLL). Although targeted therapies have improved outcomes compared to traditional chemoimmunotherapy in the front-line and relapsed or refractory settings, they are associated with resistance mutations and suboptimal outcomes in certain high-risk patients. Additionally, targeted therapies are associated with drug interactions and unique adverse effect profiles which can be challenging for patients and clinicians to manage. Ongoing studies continue to address questions regarding optimal sequencing of therapies, the role of treatment combinations, and the efficacy of next-generation novel agents. This review provides a comprehensive overview regarding the clinical management of targeted therapies for CLL and applies current literature to clinical practice.

Biology and Treatment of High-Risk CLL: Significance of Complex Karyotype

Several reports highlight the clinical significance of cytogenetic complexity, namely, complex karyotype (CK) identified though the performance of chromosome banding analysis (CBA) in chronic lymphocytic leukemia. Indeed, apart from a number of studies underscoring the prognostic and predictive value of CK in the chemo(immune)therapy era, mounting evidence suggests that CK could serve as an independent prognosticator and predictor even in patients treated with novel agents. In the present review, we provide an overview of the current knowledge regarding the clinical impact of CK in CLL, touching upon open issues related to the incorporation of CK in the clinical setting.

Frontline treatment in CLL: the case for time-limited treatment

Over the last decade, the advent of Bruton tyrosine kinase inhibitors (BTKi) has profoundly modified the therapeutic strategy in chronic lymphocytic leukemia (CLL), introducing the concept of treatment until progression. Initially, the bcl-2 inhibitor venetoclax (VEN) was used as a single agent and then was rapidly combined in VEN-based regimens associated with either anti-CD20 or with BTKi. These regimens yielded a high rate of complete remission, leading to their use as a fixed duration treatment. The decision between continuous treatment with BTKi and VEN-based combinations relies mostly on comorbidities, comedications, and patient/physician preferences. Notably, with BTKi, cardiovascular comorbidities, hypertension, and potential pharmacological interactions should be carefully evaluated. On the other hand, the risk of tumor lysis syndrome with VEN should be monitored at treatment initiation. TP53 alteration and IGHV mutational status should also be assessed, as they remain important for therapeutic decisions. Fit patients with a TP53 wild type and IGHV-mutated CLL may still benefit from fludarabine-cyclophosphamide-rituximab chemoimmunotherapy (CIT), as it may result in a very long remission duration. VEN-based treatments are well tolerated, and no additional toxicity has been observed when combined with anti-CD20 or BTKi. The 1-year fixed-duration association of VEN plus obinutuzumab was evaluated in frontline for older adult patients. Nonetheless, considering the favorable outcome, an extension of indication for fit younger patients is expected. The association of VEN and BTKi is promising, even if the follow-up is still short. It is currently being tested against CIT, BTKi continuous treatment, and VEN plus anti-CD20.

Chronic lymphocytic leukemia: 2022 update on diagnostic and therapeutic procedures

DISEASE OVERVIEW

Chronic lymphocytic leukemia (CLL) is one of the most frequent types of leukemia. It typically occurs in elderly patients and has a highly variable clinical course. Leukemic transformation is initiated by specific genomic alterations that interfere with the regulation of proliferation and of apoptosis in clonal B-cells.

DIAGNOSIS

The diagnosis is established by blood counts, blood smears, and immunophenotyping of circulating B-lymphocytes, which identify a clonal B-cell population carrying the CD5 antigen as well as typical B-cell markers.

PROGNOSIS AND STAGING

The clinical staging systems provide prognostic information by using the results of physical examination and blood counts. Various biological and genetic markers provide additional prognostic information. Deletions of the short arm of chromosome 17 (del[17p]) and/or mutations of the TP53 gene predict resistance to chemoimmunotherapy and a shorter time to progression with most targeted therapies. The CLL international prognostic index integrates genetic, biological, and clinical variables to identify distinct risk groups of patients with CLL.

THERAPY

Only patients with active or symptomatic disease or with advanced Binet or Rai stages require therapy. When treatment is indicated, several therapeutic options exist: a combination of the B-cell lymphoma 2 (BCL2) inhibitor venetoclax with obinutuzumab, monotherapy with inhibitors of Bruton tyrosine kinase (BTK) such as ibrutinib and acalabrutinib, or chemoimmunotherapy. At relapse, the initial treatment may be repeated, if the treatment-free interval exceeds 3 years. If the disease relapses earlier, therapy should be changed using an alternative regimen. Patients with a del(17p) or TP53 mutation are usually resistant to chemotherapy and should, therefore, be treated with targeted agents.

FUTURE CHALLENGES

Combinations of targeted agents are now being investigated to create efficient, potentially curative therapies of CLL with fixed duration. One of the most relevant questions currently addressed in clinical trials is the comparison of monotherapies with BTK inhibitors with fixed duration combination therapies. Moreover, the optimal sequencing of targeted therapies remains to be determined. Alternative therapies are needed for patients with BTK and BCL2 inhibitor double-refractory disease.

How to Diagnose and Treat CD5-Positive Lymphomas Involving the Spleen

Patients with CD5-expressing lymphomas presenting with splenomegaly are frequently diagnosed with chronic lymphocytic leukemia. The most important differential diagnosis is mantle cell lymphoma, both in its classical and leukemic, non-nodal forms, given its prognostic and therapeutic implications. Other small B-cell neoplasms that frequently involve the spleen and occasionally express CD5 include the splenic marginal zone lymphoma, hairy cell leukemia and, rarely, lymphoplasmacytic lymphoma. The frequency of CD5 positivity depends in part on the sensitivity of the detection methods employed. Usually, a combination of morphological, immunophenotypic and molecular findings allows for a precise sub-classification of CD5-positive, low-grade B-cell lymphomas of the spleen. Some of these tumors may display a mixture of small and larger B cells, raising the possibility of more aggressive lymphomas, such as diffuse large B-cell lymphomas (DLBCL). Approximately 5-10% of DLBCL are CD5-positive and some may manifest as primary splenic lesions. When available, the morphology of DLBCL in the splenic tissue is distinctive and a leukemic picture is very rare. In conclusion, the appropriate morphological and clinical context assisted by flow cytometry panels and/or immunohistochemistry allows the differential diagnosis of CD5-positive, non-Hodgkin, B-cell lymphomas involving the spleen.

Measurable residual disease in chronic lymphocytic leukemia: expert review and consensus recommendations

Assessment of measurable residual disease (often referred to as "minimal residual disease") has emerged as a highly sensitive indicator of disease burden during and at the end of treatment and has been correlated with time-to-event outcomes in chronic lymphocytic leukemia. Undetectable-measurable residual disease status at the end of treatment demonstrated independent prognostic significance in chronic lymphocytic leukemia, correlating with favorable progression-free and overall survival with chemoimmunotherapy. Given its utility in evaluating depth of response, determining measurable residual disease status is now a focus of outcomes in chronic lymphocytic leukemia clinical trials. Increased adoption of measurable residual disease assessment calls for standards for nomenclature and outcomes data reporting. In addition, many basic questions have not been systematically addressed. Here, we present the work of an international, multidisciplinary, 174-member panel convened to identify critical questions on key issues pertaining to measurable residual disease in chronic lymphocytic leukemia, review evaluable data, develop unified answers in conjunction with local expert input, and provide recommendations for future studies. Recommendations are presented regarding methodology for measurable residual disease determination, assay requirements and in which tissue to assess measurable residual disease, timing and frequency of assessment, use of measurable residual disease in clinical practice versus clinical trials, and the future usefulness of measurable residual disease assessment. Nomenclature is also proposed. Adoption of these recommendations will work toward standardizing data acquisition and interpretation in future studies with new treatments with the ultimate objective of improving outcomes and curing chronic lymphocytic leukemia.

Minimal Residual Disease Dynamics after Venetoclax-Obinutuzumab Treatment: Extended Off-Treatment Follow-up From the Randomized CLL14 Study

PURPOSE

The CLL14 study has established one-year fixed-duration treatment of venetoclax and obinutuzumab (Ven-Obi) for patients with previously untreated chronic lymphocytic leukemia. With all patients off treatment for at least three years, we report a detailed analysis of minimal residual disease (MRD) kinetics and long-term outcome of patients treated in the CLL14 study.

PATIENTS AND METHODS

Patients were randomly assigned to receive six cycles of obinutuzumab with 12 cycles of venetoclax or 12 cycles of chlorambucil (Clb-Obi). Progression-free survival (PFS) was the primary end point. Key secondary end points included rates of undetectable MRD and overall survival. To analyze MRD kinetics, a population-based growth model with nonlinear mixed effects approach was developed.

RESULTS

Of 432 patients, 216 were assigned to Ven-Obi and 216 to Clb-Obi. Three months after treatment completion, 40% of patients in the Ven-Obi arm (7% in the Clb-Obi arm) had undetectable MRD levels < 10^-6 by next-generation sequencing in peripheral blood. Median MRD doubling time was longer after Ven-Obi than Clb-Obi therapy (median 80 v 69 days). At a median follow-up of 52.4 months, a sustained significant PFS improvement was observed in the Ven-Obi arm compared with Clb-Obi (median not reached v 36.4 months; hazard ratio 0.33; 95% CI, 0.25 to 0.45; P < .0001). The estimated 4-year PFS rate was 74.0% in the Ven-Obi and 35.4% in the Clb-Obi arm. No difference in overall survival was observed (hazard ratio 0.85; 95% CI, 0.54 to 1.35; P = .49). No new safety signals occurred.

CONCLUSION

Appearance of MRD after Ven-Obi is significantly slower than that after Clb-Obi with more effective MRD reduction. These findings translate into a superior long-term efficacy with the majority of Ven-Obi-treated patients remaining in remission.

Optimal Management of Chronic Lymphocytic Leukemia and Economic Constraints

ABSTRACT

In this article, we carry out an overview on the management options available for chronic lymphocytic leukemia (CLL) patients and discuss possible treatment decisions, taking into account the issue of sustainability and availability. Targeted agents have shown to be superior compared with chemoimmunotherapy (CIT) in terms of progression-free survival in high-risk CLL. In the majority of studies, however, continuous treatment was compared with fixed-duration CIT and no overall survival or progression-free survival-2 (time from randomization to second progression or death) advantage could be documented. Meanwhile, a substantial financial burden on both patients and payers has raised issues about affordability and adherence to treatment. Therefore, value-based pricing of new drugs has been used to set up price negotiation policies in several countries, and fixed-duration therapy has shown to be less costly than continuous treatment. Thus, CIT continues to have a role in the treatment of CLL patients with a favorable genetic profile, that is, with a mutated IGHV gene profile and a wild-type TP53. Targeted treatment represents the preferred choice in patients with an unmutated IGHV gene configuration and/or a TP53 disruption, provided that adherence to treatment is guaranteed and bearing in mind that should costly drugs not be available for frontline treatment, new agents can be very effective as first salvage treatment.

Time-limited, Combined Regimen in Chronic Lymphocytic Leukemia: A Promising Strategy to Achieve a Drug Holiday

Chemoimmunotherapy (CIT) is defined as standard first line treatment for chronic lymphocytic leukemia (CLL) patients while patients with unfavorable biological characteristics such as unmutated immunoglobulin heavy chain (UM-IGHV) and TP53 aberration failed to benefit from it. The emergency of the small molecular targeted agents including Bruton's tyrosine kinase (BTK) inhibitor (BTKi) leads to a brand-new era, from a CIT to a chemo-free era in CLL. However, the treatment of target agents is not enough to attain a deep remission and high rate of complete remission (CR), especially in patients with high risks. The long duration brought about problems, such as cost, drug resistance and toxicity. To benefit CLL in progression free survival (PFS) and long-term remission, exploration of time-limited therapies, mainly with BTKi plus CIT and BCL2i based combination therapy has become a mainstream in clinical trials. The time-limited combination therapy shed light on the promising potentiality to attain sustainable deep remission and partly overcame the risk factors, although long term follow-up is required to consolidate the conclusion. In this review, we intend to introduce key results of clinical trials with combination therapy, discuss the achievements and limitations and put forward future direction for clinical trial design in this field.

Immune Gene Rearrangements: Unique Signatures for Tracing Physiological Lymphocytes and Leukemic Cells

The tremendous diversity of the human immune repertoire, fundamental for the defense against highly heterogeneous pathogens, is based on the ingenious mechanism of immune gene rearrangements. Rearranged immune genes encoding the immunoglobulins and T-cell receptors and thus determining each lymphocyte's antigen specificity are very valuable molecular markers for tracing malignant or physiological lymphocytes. One of their most significant applications is tracking residual leukemic cells in patients with lymphoid malignancies. This so called 'minimal residual disease' (MRD) has been shown to be the most important prognostic factor across various leukemia subtypes and has therefore been given enormous attention. Despite the current rapid development of the molecular methods, the classical real-time PCR based approach is still being regarded as the standard method for molecular MRD detection due to the cumbersome standardization of the novel approaches currently in progress within the EuroMRD and EuroClonality NGS Consortia. Each of the molecular methods, however, poses certain benefits and it is therefore expectable that none of the methods for MRD detection will clearly prevail over the others in the near future.

A 10-color flow cytometry panel for diagnosis and minimal residual disease in chronic lymphocytic leukemia

Diagnosis and minimal residual disease (MRD) monitoring of chronic lymphocytic leukemia (CLL) by flow cytometry currently requires multiple antibody panels. We added CD23 and CD200 to the EuroFlow^TM lymphoid screening tube (LST) to create a 10-color modified LST (mLST) capable of diagnosing typical CLL in a single tube. We then explored if the mLST could be used for MRD by comparing its performance to the European Research Initiative on CLL (ERIC) panel using spiked cryopreserved and fresh patient samples. Over 1 year of use in our clinical laboratory, the mLST diagnosed CLL without further immunophenotyping in 56% of samples with an abnormal clone. There was good agreement in MRD results between the mLST and ERIC panels. Therefore, the mLST can streamline CLL diagnosis by reducing technician time and the number of panels required. It may have the potential to screen for MRD in laboratories without access to dedicated panels (ERIC).

Should Undetectable Minimal Residual Disease Be the Goal of Chronic Lymphocytic Leukemia Therapy?

With the advent of highly effective novel therapies for chronic lymphocytic leukemia, conventional response assessment is not able to sensitively capture depth of response. To achieve a more precise assessment of response, minimal residual disease has been introduced to more accurately classify and quantify treatment outcomes. It is now considered a strong predictor of outcome in chronic lymphocytic leukemia, although its interpretation depends on the therapeutic context. This review discusses available methods of minimal residual disease measurement. It summarizes minimal residual disease data from pivotal clinical trials and discusses potential implications for future studies and minimal residual disease-based clinical strategies.

Stance of MRD in Non-Hodgkin's Lymphoma and its upsurge in the novel era of cell-free DNA

Cancer genomics has evolved over the years from understanding the pathogenesis of cancer to screening the future possibilities of cancer occurrence. Understanding the genetic profile of tumors holds a prognostic as well as a predictive value in this era of therapeutic surveillance, molecular remission, and precision medicine. Identifying molecular markers in tumors is the current standard of approach, and requires an efficient combination of an accessible sample type and a profoundly sensitive technique. Liquid biopsy or cell-free DNA has evolved as a novel sample type with promising results in recent years. Although cell-free DNA has significant role in various cancer types, this review focuses on its application in Non-Hodgkin's Lymphoma. Beginning with the current concept and clinical relevance of minimal residual disease in Non-Hodgkin's lymphoma, we discuss the literature on circulating DNA and its evolving application in the realm of cutting-edge technology.

From Biomarkers to Models in the Changing Landscape of Chronic Lymphocytic Leukemia: Evolve or Become Extinct

Simple Summary

Chronic lymphocytic leukemia (CLL) is characterized by a highly variable clinical course. Thus, predicting the outcome of patients with this disease is a topic of special interest. The rapidly changing treatment landscape of CLL has questioned the value of classical biomarkers and prognostic models. Herein we examine the current state-of-the-art of prognostic and predictive biomarkers in the setting of new oral targeted agents with special focus on the most controversial findings over the last years. We also discuss the available information on the role of “old” and “new” prognostic models in the era of oral small molecules.

Abstract

Chronic lymphocytic leukemia (CLL) is an extremely heterogeneous disease. With the advent of oral targeted agents (Tas) the treatment of CLL has undergone a revolution, which has been accompanied by an improvement in patient’s survival and quality of life. This paradigm shift also affects the value of prognostic and predictive biomarkers and prognostic models, most of them inherited from the chemoimmunotherapy era but with a different behavior with Tas. This review discusses: (i) the role of the most relevant prognostic and predictive biomarkers in the setting of Tas; and (ii) the validity of classic and new scoring systems in the context of Tas. In addition, a critical point of view about predictive biomarkers with special emphasis on 11q deletion, novel resistance mutations, TP53 abnormalities, IGHV mutational status, complex karyotype and NOTCH1 mutations is stated. We also go over prognostic models in early stage CLL such as IPS-E. Finally, we provide an overview of the applicability of the CLL-IPI for patients treated with Tas, as well as the emergence of new models, generated with data from patients treated with Tas.

Clinical Trial Design and Drug Approval in Oncology: A Primer for the Advanced Practitioner in Oncology

Evidenced-based practice requires timely and accurate integration of scientific advances. This presents a challenge for the oncology clinician given the robust pace of scientific discovery and the increasing number of new drug approvals and expanded indications for previously approved drugs. All currently available antineoplastic therapies have been developed through the clinical trials process. Advanced practitioners (APs) in oncology are often involved in the conduct of clinical trials as primary investigators, sub-investigators, study coordinators, or in the delivery and monitoring of care to patients enrolled in these trials. A prerequisite to evidenced-based practice is understanding how clinical trials are conducted and how to critically analyze published results of studies leading to U.S. Food & Drug Administration approval. Any AP involved in the clinical management and supportive care of patients receiving antineoplastic therapies should be able to critically review published data to glean findings that warrant a change in practice. The goals of this manuscript are to summarize key elements of the clinical trial process for oncology drug development and approval in the United States and to provide a primer for the interpretation of clinical data.

Integrated Mechanistic Model of Minimal Residual Disease Kinetics With Venetoclax Therapy in Chronic Lymphocytic Leukemia

Minimal residual disease (MRD) is an important emerging clinical end point in chronic lymphocytic leukemia (CLL). The objective of this research was to develop an integrated mechanistic model to evaluate the impact of venetoclax-rituximab combination therapy on MRD kinetics. Using data from 435 patients with relapsed or refractory CLL, an integrated model was developed and validated that accounted for venetoclax dosing and pharmacokinetics, rituximab treatment, absolute lymphocyte count, and blood and bone marrow (BM) MRD data. Simulations of venetoclax-rituximab (six cycles) combination predicted the proportion (90% confidence interval) of patients with BM MRD below 10-4 to be 57% (54-61%) and 63% (59-67%) at 12 and 24 months of treatment, respectively. Continued venetoclax treatment to 48 months only increased the predicted rate of negative BM MRD to 66% (63-70%). These results indicate that treatment with venetoclax-rituximab combination for a finite 2-year period would nearly maximize the rate of negative BM MRD (< 10-4 ). Preliminary clinical data agree with these predictions and more long-term follow-up data are awaited to confirm the same.