Standardized MRD flow and ASO IGH RQ-PCR for MRD quantification in CLL patients after rituximab-containing immunochemotherapy: a comparative analysis

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.

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.

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.

Measurable residual disease in chronic lymphocytic leukemia

Measurable residual disease (MRD) is defined as the presence of residual cancer cells after treatment in patients with clinically undetectable disease, who would otherwise be considered in complete remission. It is a highly sensitive parameter which indicates the disease burden and predicts survival in this setting of patients. In recent years, MRD has gained a role in many hematological malignancies as a surrogate endpoint for clinical trials: undetectable MRD has been correlated to longer progression free survival (PFS) and overall survival (OS). New drugs and combinations have been developed with the aim to achieve MRD negativity, which would indicate favorable prognosis. Different methods to measure MRD have also been devised, which include flow cytometry, polymerase chain reaction (PCR) and next generation sequencing (NGS), with different sensitivity and accuracy in evaluating deep remission after treatment. In this review, we will analyze the current recommendations for the detection of MRD, with particular focus on its role in Chronic Lymphocytic Leukemia (CLL), as well as the different detection methods. Moreover, we will discuss the results of clinical trials and the role of MRD in new therapeutic schemes with inhibitors and monoclonal antibodies. MRD is not currently used in the clinical practice to evaluate response to treatment, due to technical and economical limitations, but it's gaining more and more interest in trials settings, especially since the introduction of venetoclax. The use of MRD in trials will likely be followed by a broader practical application in the future. The aim of this work is to provide a reader-friendly summary of the state of art in the field, as MRD will soon become an accessible tool to evaluate our patients, predict their survival and guide physician's therapeutic choices and preferences.

Patient specific real-time PCR in precision medicine - Validation of IG/TR based MRD assessment in lymphoid leukemia

Detection of patient- and tumor-specific clonally rearranged immune receptor genes using real-time quantitative (RQ)-PCR is an accepted method in the field of precision medicine for hematologic malignancies. As individual primers are needed for each patient and leukemic clone, establishing performance specifications for the method faces unique challenges. Results for series of diagnostic assays for CLL and ALL patients demonstrate that the analytic performance of the method is not dependent on patients' disease characteristics. The calibration range is linear between 10^-1 and 10^-5 for 90% of all assays. The detection limit of the current standardized approach is between 1.8 and 4.8 cells among 100,000 leukocytes. RQ-PCR has about 90% overall agreement to flow cytometry and next generation sequencing as orthogonal methods. Accuracy and precision across different labs, and above and below the clinically applied cutoffs for minimal/measurable residual disease (MRD) demonstrate the robustness of the technique. The here reported comprehensive, IVD-guided analytical validation provides evidence that the personalized diagnostic methodology generates robust, reproducible and specific MRD data when standardized protocols for data generation and evaluation are used. Our approach may also serve as a guiding example of how to accomplish analytical validation of personalized in-house diagnostics under the European IVD Regulation.

Impact of red blood cell lysing on rare event analysis

The challenges associated with analyzing rare cells are dependent on a series of factors, which usually require large numbers of cells per sample for successful resolution. Among these is determining the minimum number of total events needed to be acquired as defined by the expected frequency of the target cell population. The choice of markers that identify the target population, as well as the event rate and the number of aborted events/second, will also determine the statistically significant detection of rare cell events. Sample preparation is another important but often overlooked factor in rare cell analysis, and in this study we examine Poisson theory and methods to determine the effect of sample manipulation on rare cell detection. After verifying the applicability of this theory, we have evaluated the potential impact of red cell lysis on rare cell analysis, and how cell rarity can be underestimated or overestimated based on erythrolytic sensitivity or resistance of healthy leukocytes and pathological rare cells. This article is protected by copyright. All rights reserved.

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.

Incorporating molecular biomarkers into the continuum of care in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a mature B-cell malignancy characterized by marked heterogeneity. Discoveries in disease biology over the past two decades have helped explain clinical variability and heralded the arrival of the targeted therapy era. In this article, we review improvements in risk stratification which have coincided with this progress, including individual biomarkers and their incorporation into prognostic models. Amidst an ever-expanding list of biomarkers, we seek to bring focus to the essential tests to improve patient care and counseling at particular times in the disease course, beginning with prognosis at diagnosis. The majority of patients do not require treatment at the time of diagnosis, making time-to-first-treatment a key initial prognostic concern. Prognostic and predictive biomarkers are then considered at subsequent major junctures, including at the time of treatment initiation, while on therapy, and at the time of relapse on novel agents.

Measurable residual disease in the treatment of chronic lymphocytic leukemia

Treatment outcomes of chronic lymphocytic leukemia (CLL) have improved since chemoimmunotherapy and novel drugs became available for CLL treatment; therefore, more sensitive methods to evaluate residual CLL cells in patients are required. Measurable residual disease (MRD) has been assessed in several clinical trials on CLL using flow cytometry, real-time quantitative PCR (RQ-PCR) with allele-specific oligonucleotide (ASO) primers, and high-throughput sequencing. MRD assessment is useful to predict the treatment outcomes in the context of chemotherapy and treatment with novel drugs such as venetoclax. In this review, we discuss major techniques for MRD assessment, data from relevant clinical trials, and the future of MRD assessment in CLL treatment.

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.

Early treatment with FCR versus watch and wait in patients with stage Binet A high-risk chronic lymphocytic leukemia (CLL): a randomized phase 3 trial

We report a randomized prospective phase 3 study (CLL7), designed to evaluate the efficacy of fludarabine, cyclophosphamide, and rituximab (FCR) in patients with an early-stage high-risk chronic lymphocytic leukemia (CLL). Eight hundred patients with untreated-stage Binet A disease were enrolled as intent-to-treat population and assessed for four prognostic markers: lymphocyte doubling time <12 months, serum thymidine kinase >10 U/L, unmutated IGHV genes, and unfavorable cytogenetics (del(11q)/del(17p)/trisomy 12). Two hundred and one patients with ≥2 risk features were classified as high-risk CLL and 1:1 randomized to receive either immediate therapy with 6xFCR (Hi-FCR, 100 patients), or to be observed according to standard of care (Hi-W&W, 101 patients). The overall response rate after early FCR was 92.7%. Common adverse events were hematological toxicities and infections (61.0%/41.5% of patients, respectively). After median observation time of 55.6 (0-99.2) months, event-free survival was significantly prolonged in Hi-FCR compared with Hi-W&W patients (median not reached vs. 18.5 months, p < 0.001). There was no significant overall survival benefit for high-risk patients receiving early FCR therapy (5-year OS 82.9% in Hi-FCR vs. 79.9% in Hi-W&W, p = 0.864). In conclusion, although FCR is efficient to induce remissions in the Binet A high-risk CLL, our data do not provide evidence that alters the current standard of care "watch and wait" for these patients.

Minimal Residual Disease Assessment in CLL: Ready for Use in Clinical Routine?

The introduction of chemoimmunotherapy and more recently the implementation of novel agents into first-line and relapse treatment have substantially improved treatment outcomes in patients with chronic lymphocytic leukaemia (CLL). With longer progression-free survival and more frequently observed deep remissions there is an emerging need for sensitive methods quantitating residual disease after therapy. Over the last decade, assessment of minimal residual disease (MRD) has increasingly been implemented in CLL trials. The predictive value of MRD status on survival outcomes has repeatedly been proven in the context of chemoimmunotherapy and cellular therapies. Recent data suggests a similar correlation for Bcl-2 inhibitor-based therapy. While the relevance of MRD assessment as a surrogate endpoint in clinical trials is largely undisputed, its role in routine clinical practice has not yet been well defined. This review outlines current methods of MRD detection in CLL and summarizes MRD data from relevant trials. The significance of MRD testing in clinical studies and in routine patient care is assessed and new MRD-guided treatment strategies are discussed.

Obinutuzumab pretreatment abrogates tumor lysis risk while maintaining undetectable MRD for venetoclax + obinutuzumab in CLL

Early data on venetoclax-containing regimens for the treatment of chronic lymphocytic leukemia (CLL) show promising results with deep remissions, but are hampered by potential risk for tumor lysis syndrome (TLS). Whether optimal duration of venetoclax treatment can be guided by minimal residual disease (MRD) is currently unknown. To study whether TLS risk can be mitigated in an unfit population by introducing preinduction, and whether MRD-guided duration of venetoclax treatment is a feasible and efficacious approach, we performed the Dutch-Belgian Cooperative Trial Group for Hemato-oncology (HOVON) 139/GIVE trial. The study treatment consists of 4 treatment phases: preinduction (2 cycles obinutuzumab), induction I (6 cycles obinutuzumab and venetoclax), induction II (6 cycles venetoclax), and a randomization phase (group A: maintenance with 12 additional cycles of venetoclax irrespective of MRD; group B: MRD guided venetoclax maintenance with a maximum of 12 cycles). Here we report on a planned interim safety analysis as well as preliminary efficacy and MRD data of the first 30 patients enrolled. Downgrading of TLS risk after preinduction occurred in 25 patients: 3 from high to medium, 3 from high to low, and 19 from medium to low risk. No patient remained high risk. From these 30 patients, peripheral blood MRD data were obtained for 28 patients at the end of induction II (6 months after the last obinutuzumab dose), of whom 26 had undetectable MRD levels, and for 18 patients who reached the 3-month after-randomization point, of whom 16 had undetectable MRD levels. Obinutuzumab preinduction is tolerated well in these unfit patients and results in abrogating high TLS risk in all patients. Preliminary data indicate that efficacy is maintained with a high proportion of patients with undetectable MRD levels after combination treatment.

Minimal Residual Disease in Chronic Lymphocytic Leukemia: A New Goal?

In chronic lymphocytic leukemia (CLL), there is a growing interest for minimal residual disease (MRD) monitoring, due to the availability of drug combinations capable of unprecedented complete clinical responses. The standardized and most commonly applied methods to assess MRD in CLL are based on flow cytometry (FCM) and, to a lesser extent, real-time quantitative PCR (RQ-PCR) with allele-specific oligonucleotide (ASO) primers of immunoglobulin heavy chain genes (IgH). Promising results are being obtained using droplet digital PCR (ddPCR) and next generation sequencing (NGS)-based approaches, with some advantages and a potential higher sensitivity compared to the standardized methodologies. Plasma cell-free DNA can also be explored as a more precise measure of residual disease from all different compartments, including the lymph nodes. From a clinical point of view, CLL MRD quantification has proven an independent prognostic marker of progression-free survival (PFS) and overall survival (OS) after chemoimmunotherapy as well as after allogeneic transplantation. In the era of mechanism-driven drugs, the paradigms of CLL treatment are being revolutionized, challenging the use of chemoimmunotherapy even in first-line. The continuous administration of ibrutinib single agent has led to prolonged PFS and OS in relapsed/refractory and treatment naïve CLL, including those with TP53 deletion/mutation or unmutated IGHV genes, though the clinical responses are rarely complete. More recently, chemo-free combinations of venetoclax+rituximab, venetoclax+obinutuzumab or ibrutinib+venetoclax have been shown capable of inducing undetectable MRD in the bone marrow, opening the way to protocols exploring a MRD-based duration of treatment, aiming at disease eradication. Thus, beside a durable disease control desirable particularly for older patients and/or for those with comorbidities, a MRD-negative complete remission is becoming a realistic prospect for CLL patients in an attempt to obtain a long-lasting eradication and possibly cure of the disease. Here we discuss the standardized and innovative technical approaches for MRD detection in CLL, the clinical impact of MRD monitoring in chemoimmunotherapy and chemo-free trials and the future clinical implications of MRD monitoring in CLL patients outside of clinical trials.

SOHO State of the Art Updates and Next Questions: The Conundrum in Assessing the Therapy Response of Patients With Chronic Lymphocytic Leukemia

In 2018, the International Workshop on Chronic Lymphocytic Leukemia (iwCLL) updated the guidelines for diagnosis, indications for treatment, response assessment, and supportive management of patients with chronic lymphocytic leukemia. Included were definitions for response, which incorporated consideration of the significance of minimal residual disease. Here we discuss the clinical significance of complete response or partial response, as defined in the 2018 iwCLL guidelines, and the relative value of assessing for minimal residual disease.

Minimal Residual Disease Quantification in Chronic Lymphocytic Leukemia: Clinical Significance and Flow Cytometric Methods

The very sensitive quantification of leukemia cells that persist in chronic lymphocytic leukemia patients after successful therapy is steadily gaining interest with clinical scientists. Minimal residual disease (MRD) has demonstrated prognostic significance in the context of different treatment modalities leading to its approval as an intermediate endpoint for licensure in randomized trials by the European Medicine Agency. Data supporting the clinical impact of MRD as well as a highly standardized and broadly available method for MRD assessments by flow cytometry are described herein. Examples of gating strategies are provided with comprehensive explanations to allow the reader the application of the technology to blood and bone samples with high and very low level MRD, respectively. This chapter has a particular focus on samples acquired shortly after anti-CD20 treatment. The standardization developed by the EuroFlow consortium is additionally described as technical basis for reproducible and standardized flow cytometric MRD assessments.

Flow Cytometric MRD Detection in Selected Mature B-Cell Malignancies

The quantification of submicroscopic minimal residual disease (MRD) after therapy proved to have independent prognostic significance in many mature B-cell malignancies. With the advent of routine benchtop cytometers capable of simultaneously analyzing ≥4 colors and with improved standardization, flow cytometry has become the method of choice for MRD assessments in some lymphoma entities. Herein we describe general aspects of flow cytometric standardization. Chronic lymphocytic leukemia and multiple myeloma (MM) are used as examples to explain the technical standardization of flow cytometry for MRD detection according to EuroFlow strategies. MRD data acquisition and detailed analysis using a newly developed approach (so-called next generation flow, NGF) in MM is a particular focus of this chapter.

[Minimal residual disease in chronic lymphocytic leukemia: A still current issue in 2018]

Minimal residual disease (MRD) is widely used in oncohematology. In chronic lymphocytic leukemia (CLL), it can be measured by flow cytometry or polymerase chain reaction and is getting a greater place, owing to the dramatic therapeutic advances in the management this disease. As MRD decrease after chemoimmunotherapy is associated with improved progression free and overall survivals, its measure is now recommended as a surrogate marker for cytotoxic drugs licensures. This association is independent from treatment received and raises a few questions, such as sequential MRD measures to stop treatment in case of an early deep response and on the opposite, treatment continuation until reaching undetectable MRD (with the possible use of maintenance therapy). Furthermore, following MRD after a cytotoxic treatment could lead clinical trials investigators to propose pre-emptive treatments in case of MRD re-growth, to avoid overt relaspe. MRD re-growth kinetics and CD4 count after treatment completion can improve MRD-based survival predictions. On the other hand, BCR inhibitors do not lead to undetectable MRD, but their association with chemoimmunotherapy increases the proportion of patients reaching that goal. Moreover, BCL2 inhibitors do lead to deep response including in the relapse/refractory setting, giving to MRD a central place in currently investigated treatments evaluation.

Methods and role of minimal residual disease after stem cell transplantation

Relapse is the major cause of treatment failure after stem cell transplantation. Despite the fact that relapses occurred even if transplantation was performed in complete remission, it is obvious that minimal residual disease is present though not morphologically evident. Since adaptive immunotherapy by donor lymphocyte infusion or other novel cell therapies as well as less toxic drugs, which can be used after transplantation, the detection of minimal residual disease (MRD) has become a clinical important variable for outcome. Besides the increasing options to treat MRD, the most advanced technologies currently allow to detect residual malignant cells with a sensitivity of 10^-5 to 10^-6.Under the patronage of the European Society for Blood and Marrow Transplantation (EBMT) and the American Society for Blood and Marrow Transplantation (ASBMT) the 3rd workshop was held on 4/5 November 2016 in Hamburg/Germany, with the aim to present an up-to-date status of epidemiology and biology of relapse and to summarize the currently available options to prevent and treat post-transplant relapse. Here the current methods and role of minimal residual disease for myeloid and lymphoid malignancies are summarized.

Obinutuzumab plus bendamustine in previously untreated patients with CLL: a subgroup analysis of the GREEN study

GREEN (NCT01905943) is a non-randomized, open-label phase IIIb study investigating obinutuzumab alone or plus chemotherapy in chronic lymphocytic leukemia (CLL). We report a preplanned subgroup analysis of 158 previously untreated CLL patients receiving obinutuzumab-bendamustine (G-B). Patients received six 28-day cycles (C) of G-B: obinutuzumab day (D)1/D2 of C1 (25 mg D1/975 mg D2), 1000 mg D8 and D15 of C1, and D1 of C2-6; and bendamustine 70/90 mg/m2 D1 and D2 of C1-6. The primary endpoint was safety/tolerability. Grade ≥3 adverse events (AEs) occurred in 82.3% of patients, including neutropenia (49.4%), thrombocytopenia (12.0%) and febrile neutropenia (10.8%). Serious AEs included neutropenia (12.7%), febrile neutropenia (9.5%) and pneumonia (7.6%). Rates of grade ≥3 infections and infusion-related reactions were 20.3% and 17.1%, respectively. Due to tumor lysis syndrome (TLS; 8.2%), including two associated fatalities (one in another study cohort), additional risk-minimization measures were implemented. Overall response rate was 81.0%. After 32.8 months' median observation time, 2-year progression-free survival was 81.8%. Minimal residual disease was undetectable in 59.5% (94/158) and 27.8% (44/158) of patients for blood and bone marrow, respectively. Frontline G-B appears to have manageable toxicity with clinical activity in CLL. Careful TLS risk assessment, pretreatment and monitoring is required.

CLL2-BXX Phase II trials: sequential, targeted treatment for eradication of minimal residual disease in chronic lymphocytic leukemia

AIM

Four Phase II trials (clinical trials numbers: NCT02345863, NCT02401503, NCT02445131 and NCT02689141) evaluate a different combination of targeted agents in an all-comer population of approximately 60 patients with chronic lymphocytic leukemia irrespective of prior treatment, physical fitness and genetic risk factors. Patients with a higher tumor load start with a debulking treatment with bendamustine. The subsequent induction and maintenance treatment with an anti-CD20 antibody (obinutuzumab or ofatumumab) and a targeted oral agent (ibrutinib, idelalisib or venetoclax) are continued until achievement of a complete response and minimal residual disease negativity.

CONCLUSION

This strategy represents a new era of chronic lymphocytic leukemia therapy where chemotherapy is increasingly replaced by targeted agents and treatment duration is tailored to the patient's individual tumor load and response.

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

Purpose To determine the value of minimal residual disease (MRD) assessments, together with the evaluation of clinical response in chronic lymphocytic leukemia according to the 2008 International Workshop on Chronic Lymphocytic Leukemia criteria. Patients and Methods Progression-free survival (PFS) and overall survival of 554 patients from two randomized trials of the German CLL Study Group (CLL8: fludarabine and cyclophosphamide [FC] v FC plus rituximab; CLL10: FC plus rituximab v bendamustine plus rituximab) were analyzed according to MRD assessed in peripheral blood at a threshold of 10^-4 and clinical response. The prognostic value of different parameters defining a partial response (PR) was further investigated. Results Patients with MRD-negative complete remission (CR), MRD-negative PR, MRD-positive CR, and MRD-positive PR experienced a median PFS from a landmark at end of treatment of 61 months, 54 months, 35 months, and 21 months, respectively. PFS did not differ significantly between MRD-negative CR and MRD-negative PR; however, PFS was longer for MRD-negative PR than for MRD-positive CR ( P = .048) and for MRD-positive CR compared with MRD-positive PR ( P = .002). Compared with MRD-negative CR, only patients with MRD-positive PR had a significantly shorter overall survival (not reached v 72 months; P = .001), whereas there was no detectable difference for patients with MRD-negative PR or MRD-positive CR ( P = 0.612 and P = 0.853, respectively). Patients with MRD-negative PR who presented with residual splenomegaly had only a similar PFS (63 months) compared with patients with MRD-negative CR (61 months; P = .354), whereas patients with MRD-negative PR with lymphadenopathy showed a shorter PFS (31 months; P < .001). Conclusion MRD quantification allows for improved PFS prediction in both patients who achive PR and CR, which thus supports its application in all responders. In contrast to residual lymphadenopathy, persisting splenomegaly does not impact outcome in patients with MRD-negative PR.

A model for predicting effect of treatment on progression-free survival using MRD as a surrogate end point in CLL

Our objective was to evaluate minimal residual disease (MRD) at the end of induction treatment with chemoimmunotherapy as a surrogate end point for progression-free survival (PFS) in chronic lymphocytic leukemia (CLL) based on 3 randomized, phase 3 clinical trials (ClinicalTrials.gov identifiers NCT00281918, NCT00769522, and NCT02053610). MRD was measured in peripheral blood (PB) from treatment-naïve patients in the CLL8, CLL10, and CLL11 clinical trials, and quantified by 4-color flow cytometry or allele-specific oligonucleotide real-time quantitative polymerase chain reaction. A meta-regression model was developed to predict treatment effect on PFS using treatment effect on PB-MRD. PB-MRD levels were measured in 393, 337, and 474 patients from CLL8, CLL10, and CLL11, respectively. The model demonstrated a statistically significant relationship between treatment effect on PB-MRD and treatment effect on PFS. As the difference between treatment arms in PB-MRD response rates increased, a reduction in the risk of progression or death was observed; for each unit increase in the (log) ratio of MRD^- rates between arms, the log of the PFS hazard ratio decreased by -0.188 (95% confidence interval, -0.321 to -0.055; P = .008). External model validation on the REACH trial and sensitivity analyses confirm the robustness and applicability of the surrogacy model. Our surrogacy model supports use of PB-MRD as a primary end point in randomized clinical trials of chemoimmunotherapy in CLL. Additional CLL trial data are required to establish a more precise quantitative relationship between MRD and PFS, and to support general applicability of MRD surrogacy for PFS across diverse patient characteristics, treatment regimens, and different treatment mechanisms of action.

Pharmacokinetics, safety, and efficacy of subcutaneous versus intravenous rituximab plus chemotherapy as treatment for chronic lymphocytic leukaemia (SAWYER): a phase 1b, open-label, randomised controlled non-inferiority trial

BACKGROUND

Part one of the two-part SAWYER study predicted that subcutaneous rituximab 1600 mg would achieve trough serum concentrations that were non-inferior to those achieved with intravenous rituximab 500 mg/m(2) in patients with chronic lymphocytic leukaemia. In part two of the study, we aimed to confirm the pharmacokinetic non-inferiority of subcutaneous rituximab, and investigate its safety and efficacy.

METHODS

We did this phase 1b, open-label, randomised controlled non-inferiority study at 68 centres in 19 countries in Europe, North America, South America, and Australasia. Patients aged 18 years or older with untreated chronic lymphocytic leukaemia were randomly assigned, via an interactive voice-response system with a permuted block randomisation scheme (block size of ten), to receive subcutaneous rituximab 1600 mg or intravenous rituximab 500 mg/m(2) plus fludarabine and cyclophosphamide every 4 weeks for up to six cycles. In cycle one, all patients received intravenous rituximab 375 mg/m(2). Randomisation was stratified by Binet stage and fludarabine and cyclophosphamide administration route (oral vs intravenous). Study investigators and patients were not masked to group allocation, but allocation was concealed from the statistician, clinical scientist, and clinical pharmacologist. The primary endpoint was trough serum concentration at cycle five, with a non-inferiority margin of 0·8 for the adjusted geometric mean ratio of the subcutaneous to the intravenous dose. We did the primary analysis in patients in the intention-to-treat population with complete pharmacokinetic data (pharmacokinetic population). This trial is registered with ClinicalTrials.gov, number NCT01292603, and is ongoing, although the treatment stage is now complete.

FINDINGS

Between Aug 20, 2012, and June 17, 2013, we randomly assigned 176 patients to receive subcutaneous rituximab (n=88) or intravenous rituximab (n=88); 134 (76%) patients comprised the pharmacokinetic population. As of May 7, 2014, median follow-up was 13·9 months (IQR 11·9-16·0) for patients in the subcutaneous group and 14·1 months (11·6-16·5) for patients in the intravenous group. At cycle five, the geometric mean trough serum concentration in patients given subcutaneous rituximab was non-inferior to that in patients given intravenous rituximab (97·5 μg/mL vs 61·5 μg/mL), with an adjusted geometric mean ratio of 1·53 (90% CI 1·27-1·85). In the safety analysis, the proportion of patients reporting adverse events was similar between the subcutaneous and intravenous groups (all grades: 82 [96%] of 85 patients and 81 [91%] of 89 patients; serious adverse events: 25 [29%] and 29 [33%] patients; grade ≥3: 59 [69%] and 63 [71%] patients, respectively). The most common adverse event of grade 3 or higher was neutropenia (48 [56%] patients in the subcutaneous group and 46 [52%] patients in the intravenous group); the most common serious adverse event was febrile neutropenia (n=9 [11%] and n=4 [4%], respectively). We recorded administration-related reactions in 37 (44%) patients given subcutaneous rituximab and 40 (45%) patients given the intravenous dose, with differences between administration routes for injection-site erythema (n=10 [12%] and n=0, respectively) and nausea (n=2 [2%] and n=11 [12%], respectively). More patients reported local cutaneous reactions after subcutaneous rituximab (n=36 [42%]) than after intravenous rituximab (n=2 [2%]); most of these reactions were grade 1 or 2.

INTERPRETATION

When combined with fludarabine and cyclophosphamide, subcutaneous rituximab 1600 mg achieved trough serum concentrations that were pharmacokinetically non-inferior to those achieved with intravenous rituximab 500 mg/m(2), with a similar safety and efficacy profile between the two groups. Treatment with subcutaneous rituximab should allow patients with chronic lymphocytic leukaemia to receive clinical benefit from the drug via a more convenient delivery method than the intravenous route, and might also be used in combination regimens with approved and emerging oral regimens.

FUNDING

F Hoffmann-La Roche.

Alemtuzumab consolidation in chronic lymphocytic leukaemia: a phase I/II multicentre trial

OBJECTIVE

Despite high rates of long-lasting remissions in patients with chronic lymphocytic leukaemia (CLL) treated with chemoimmunotherapy, none of the current therapeutic approaches is curative with the exception of allogeneic transplantation. One strategy to extend progression-free survival and long-term survival might be the establishment of consolidation therapies.

METHODS

In this trial, patients with complete or partial second remission after fludarabine-based treatment received consolidation therapy with alemtuzumab. The aim of this phase I/II trial was to determine the maximal tolerable dose (MTD) of alemtuzumab consolidation and to evaluate safety and efficacy in patients who responded to second-line fludarabine-based treatment. Thirteen patients in complete (CR) or partial remission (PR) received alemtuzumab dose escalation starting with 10 mg intravenously (iv) once weekly for 8 wk and increasing in 10-mg intervals per dose level.

RESULTS

The main dose-limiting toxicities (DLTs) were infectious complications, and the MTD was determined at 10 mg. After alemtuzumab consolidation, seven of 13 patients (53%) were in CR, and four of these patients (30.7%) achieved minimal residual disease (MRD) negativity (<1 × 10E-4). At a median follow-up of 71.5 months, four patients were progression-free, with a median progression-free survival (PFS) of 28.5 months after the end of second-line treatment.

CONCLUSION

The results provide a safe and efficient schedule with weekly intravenous application of 10 mg of alemtuzumab as a consolidation regime in patients with CLL.

Diagnosis and treatment of chronic lymphocytic leukemia: recommendations from the Brazilian Group of Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia is characterized by clonal proliferation and progressive accumulation of B-cell lymphocytes that typically express CD19⁺, CD5⁺ and CD23⁺. The lymphocytes usually infiltrate the bone marrow, peripheral blood, lymph nodes, and spleen. The diagnosis is established by immunophenotyping circulating B-lymphocytes, and prognosis is defined by two staging systems (Rai and Binet) established by physical examination and blood counts, as well as by several biological and genetic markers. In this update, we present the recommendations from the Brazilian Group of Chronic Lymphocytic Leukemia for the diagnosis and treatment of chronic lymphocytic leukemia. The following recommendations are based on an extensive literature review with the aim of contributing to more uniform patient care in Brazil and possibly in other countries with a similar social–economic profile.

A complementary role of multiparameter flow cytometry and high-throughput sequencing for minimal residual disease detection in chronic lymphocytic leukemia: an European Research Initiative on CLL study

In chronic lymphocytic leukemia (CLL) the level of minimal residual disease (MRD) after therapy is an independent predictor of outcome. Given the increasing number of new agents being explored for CLL therapy, using MRD as a surrogate could greatly reduce the time necessary to assess their efficacy. In this European Research Initiative on CLL (ERIC) project we have identified and validated a flow-cytometric approach to reliably quantitate CLL cells to the level of 0.0010% (10⁻⁵). The assay comprises a core panel of six markers (i.e. CD19, CD20, CD5, CD43, CD79b and CD81) with a component specification independent of instrument and reagents, which can be locally re-validated using normal peripheral blood. This method is directly comparable to previous ERIC-designed assays and also provides a backbone for investigation of new markers. A parallel analysis of high-throughput sequencing using the ClonoSEQ assay showed good concordance with flow cytometry results at the 0.010% (10⁻⁴) level, the MRD threshold defined in the 2008 International Workshop on CLL guidelines, but it also provides good linearity to a detection limit of 1 in a million (10⁻⁶). The combination of both technologies would permit a highly sensitive approach to MRD detection while providing a reproducible and broadly accessible method to quantify residual disease and optimize treatment in CLL.

Eliminating minimal residual disease as a therapeutic end point: working toward cure for patients with CLL

Deep remission and prolonged disease-free survival can be achieved with first-line chemoimmunotherapy (CIT), such as combined fludarabine, cyclophosphamide, and rituximab, in the majority of patients with chronic lymphocytic leukemia (CLL). More modest results are reported with less intense regimens like obinutuzumab plus chlorambucil. Clinical assessment has limited sensitivity in detecting residual disease responsible for subsequent relapse, even including morphologic bone marrow (BM) evaluation. Multicolor flow cytometry and polymerase chain reaction (PCR)-based methods can detect minimal residual disease (MRD) to a sensitivity of ≥1:10,000 (10(-4)). Achieving BM MRD-negative complete remission (CR) is associated with superior progression-free survival (PFS) and overall survival; MRD status is the single best posttreatment predictor of long-term outcomes after CIT. Newer oral B-cell receptor signaling pathway inhibitors are highly effective at controlling disease, but best monotherapy responses are typically partial remission, and patients must remain on treatment to maintain disease control. Therapeutic progress is still needed for CLL. We propose that targeting MRD provides opportunity to realize this progress. Achieving BM MRD-negative CR is a prerequisite for long-term unmaintained disease-free survival and potential for cure. We review available methodologies for detecting MRD and correlations with posttreatment outcomes. We discuss the potential utility of MRD to direct individualized therapy. Finally, we discuss the importance of MRD-negative status as a surrogate marker for longer PFS in clinical studies to allow more rapid determination of clinical benefit.

Reprint of: Back to the future! The evolving role of maintenance therapy after hematopoietic stem cell transplantation

Relapse is a devastating event for patients with hematologic cancers treated with hematopoietic stem cell transplantation. In most situations, relapse treatment options are limited. Maintenance therapy offers the possibility of delaying or avoiding disease recurrence, but its role remains unclear in most conditions that we treat with transplantation. Here, Dr. Hourigan presents an overview of minimal residual disease (MRD) measurement in hematologic malignancies and the applicability of MRD-based post-transplantation interventions. Dr. McCarthy reviews current knowledge of maintenance therapy in the autologous transplantation context, with emphasis on immunologic interventions and immune modulation strategies designed to prevent relapse. Dr. de Lima discusses current lines of investigation in disease recurrence prevention after allogeneic transplantation, focusing on acute myeloid leukemia and myelodysplastic syndrome.

Update on the molecular pathogenesis and targeted approaches of mantle cell lymphoma: summary of the 12th annual conference of the European Mantle Cell Lymphoma Network

Mantle cell lymphoma (MCL) is a distinct subtype of malignant lymphoma which is characterized by the chromosomal translocation t(11;14)(q13;q32) resulting in constitutional overexpression of cyclin D1 and cell cycle dysregulation in almost all cases. Clinically, MCL shows an aggressive clinical course with a continuous relapse pattern and a median survival of only 3-5 years. However, recently a subset of 15% long-term survivors has been identified with a rather indolent clinical course. Targeted strategies include the proteasome inhibitors, immune modulatory drugs (IMiDs), mammalian target of rapamycin (mTOR) inhibitors and especially inhibitors of the B-cell receptor pathway. Our recent annual conference focused on the molecular pathogenesis of the disease and how these underlying molecular alterations may guide the selection and integration of innovative approaches for therapy. This review of the meeting covers in particular the identification of indolent cases, and deals with the role of the B-cell receptor pathway in MCL, as well as the detection of minimal residual disease and implementation of molecular approaches in current clinical trials.

Chlorambucil plus rituximab with or without maintenance rituximab as first-line treatment for elderly chronic lymphocytic leukemia patients

In a phase II trial, we evaluated chlorambucil and rituximab (CLB-R) as first-line induction treatment with or without R as maintenance for elderly chronic lymphocytic leukemia (CLL) patients. Treatment consisted of eight 28-day cycles of CLB (8 mg/m(2) /day, days 1-7) and R (day 1 of cycle 3, 375 mg/m(2) ; cycles 4-8, 500 mg/m(2) ). Responders were randomized to 12 8-week doses of R (375 mg/m(2) ) or observation. As per intention-to-treat analysis, 82.4% (95% CI, 74.25-90.46%) of 85 patients achieved an overall response (OR), 16.5% a complete response (CR), 2.4% a CR with incomplete bone marrow recovery. The OR was similar across Binet stages (A 86.4%, B 81.6%, and C 78.6%) and age categories (60-64 years, 92.3%; 65-69, 85.2%; 70-74, 75.0%; ≥75, 81.0%). CLB-R was well tolerated. After a median follow-up of 34.2 months, the median progression-free survival (PFS) was 34.7 months (95% CI, 33.1-39.5). TP53 abnormalities, complex karyotype, and low CD20 gene expression predicted lack of response; SF3B1 mutation and BIRC3 disruption low CR rates. IGHV mutations significantly predicted PFS. R maintenance tended towards a better PFS than observation and was safe and most beneficial for patients in partial response and for unmutated IGHV cases. CLB-R represents a promising option for elderly CLL patients.

Minimal residual disease monitoring in chronic lymphocytic leukaemia patients. A comparative analysis of flow cytometry and ASO IgH RQ-PCR

Minimal residual disease (MRD) is becoming increasingly important in chronic lymphocytic leukaemia (CLL) as treatment strategies are progressively improving. The primary objective of this study was to compare the applicability of three different flow cytometric approaches: basic 4-colour analysis, European Research Initiative in CLL (ERIC) consensus method and 8-colour analysis. Secondly, we investigated the sensitivity and specificity of flow cytometry (FC) compared to molecular analyses for MRD detection. A total of 462 CLL samples were evaluated by basic FC; in 143, ERIC consensus method was also performed and all three FC methodologies were applied in a subgroup of 10 cases. No discordance in defining MRD-positive/negative samples was observed between the FC methods; within positive samples, the ERIC consensus method and 8-colour analysis showed the most accurate results. MRD was analysed by FC and polymerase chain reaction (PCR) in 243 cases: concordant results were obtained in 199/243 samples (81·9%); 42/243 were FC-/PCR+. Overall, the sensitivity and specificity of FC compared to PCR was 96·5% and 77·2%, respectively. Both FC and PCR proved suitable for the detection of MRD and prediction of progression-free survival, which was significantly reduced in MRD-positive patients, regardless of the methodology. These results offer the rationale for a strategy to monitor MRD in CLL patients.

Eradication of bone marrow minimal residual disease may prompt early treatment discontinuation in CLL

The high complete remission rate with first-line combined fludarabine, cyclophosphamide, and rituximab (FCR) begs the question of the value of minimal residual disease (MRD)-negative status as a treatment end point. We report on 237 patients with chronic lymphocytic leukemia who received first-line FCR. MRD was prospectively assessed by 4-color flow cytometry in bone marrow after course 3 and at final response assessment. After course 3 and at final response assessment, 17% and 43% of patients were MRD negative in bone marrow, respectively. A mutated immunoglobulin heavy chain variable gene and trisomy 12 were independently associated with MRD-negative status both after 3 courses of FCR and at final response assessment in multivariable analyses (MVAs). MRD-negative status was independently associated with significantly longer progression-free survival (PFS) and overall survival (OS) in MVA (P = .03 and .02, respectively). This association was confirmed also on landmark MVA at the time of MRD assessment (P = .04 and .05, respectively). MRD-negative patients had comparable PFS and OS, independent of the number of courses received or interim staging. Early MRD eradication may be a desirable goal, prompting consideration of early discontinuation of treatment. This trial was registered at www.clinicaltrials.gov as #NCT00759798.

Obinutuzumab plus chlorambucil in patients with CLL and coexisting conditions

BACKGROUND

The monoclonal anti-CD20 antibody rituximab, combined with chemotherapeutic agents, has been shown to prolong overall survival in physically fit patients with previously untreated chronic lymphocytic leukemia (CLL) but not in those with coexisting conditions. We investigated the benefit of the type 2, glycoengineered antibody obinutuzumab (also known as GA101) as compared with that of rituximab, each combined with chlorambucil, in patients with previously untreated CLL and coexisting conditions.

METHODS

We randomly assigned 781 patients with previously untreated CLL and a score higher than 6 on the Cumulative Illness Rating Scale (CIRS) (range, 0 to 56, with higher scores indicating worse health status) or an estimated creatinine clearance of 30 to 69 ml per minute to receive chlorambucil, obinutuzumab plus chlorambucil, or rituximab plus chlorambucil. The primary end point was investigator-assessed progression-free survival.

RESULTS

The patients had a median age of 73 years, creatinine clearance of 62 ml per minute, and CIRS score of 8 at baseline. Treatment with obinutuzumab-chlorambucil or rituximab-chlorambucil, as compared with chlorambucil monotherapy, increased response rates and prolonged progression-free survival (median progression-free survival, 26.7 months with obinutuzumab-chlorambucil vs. 11.1 months with chlorambucil alone; hazard ratio for progression or death, 0.18; 95% confidence interval [CI], 0.13 to 0.24; P<0.001; and 16.3 months with rituximab-chlorambucil vs. 11.1 months with chlorambucil alone; hazard ratio, 0.44; 95% CI, 0.34 to 0.57; P<0.001). Treatment with obinutuzumab-chlorambucil, as compared with chlorambucil alone, prolonged overall survival (hazard ratio for death, 0.41; 95% CI, 0.23 to 0.74; P=0.002). Treatment with obinutuzumab-chlorambucil, as compared with rituximab-chlorambucil, resulted in prolongation of progression-free survival (hazard ratio, 0.39; 95% CI, 0.31 to 0.49; P<0.001) and higher rates of complete response (20.7% vs. 7.0%) and molecular response. Infusion-related reactions and neutropenia were more common with obinutuzumab-chlorambucil than with rituximab-chlorambucil, but the risk of infection was not increased.

CONCLUSIONS

Combining an anti-CD20 antibody with chemotherapy improved outcomes in patients with CLL and coexisting conditions. In this patient population, obinutuzumab was superior to rituximab when each was combined with chlorambucil. (Funded by F. Hoffmann-La Roche; ClinicalTrials.gov number, NCT01010061.).

Back to the future! The evolving role of maintenance therapy after hematopoietic stem cell transplantation

Relapse is a devastating event for patients with hematologic cancers treated with hematopoietic stem cell transplantation. In most situations, relapse treatment options are limited. Maintenance therapy offers the possibility of delaying or avoiding disease recurrence, but its role remains unclear in most conditions that we treat with transplantation. Here, Dr. Hourigan presents an overview of minimal residual disease (MRD) measurement in hematologic malignancies and the applicability of MRD-based post-transplantation interventions. Dr. McCarthy reviews current knowledge of maintenance therapy in the autologous transplantation context, with emphasis on immunologic interventions and immune modulation strategies designed to prevent relapse. Dr. de Lima discusses current lines of investigation in disease recurrence prevention after allogeneic transplantation, focusing on acute myeloid leukemia and myelodysplastic syndrome.

TP53, SF3B1, and NOTCH1 mutations and outcome of allotransplantation for chronic lymphocytic leukemia: six-year follow-up of the GCLLSG CLL3X trial

This trial update shows that allotransplantation can provide long-term minimal residual disease–negative disease control in poor-risk chronic lymphocytic leukemia. Six-year survival is close to 60% and is independent of the presence of TP53, SF3B1, and NOTCH1 mutations in the tumor clone.

Retrospective monitoring of minimal residual disease using hairpin-shaped clone specific primers in B-cell lymphoma affected dogs

Lymphoma is one of the most common forms of cancer in dogs as it is in humans but, unlike humans, the cure rates in canines are still very low. Despite the fact that high grade B-cell lymphomas are considered to be chemotherapy responsive, almost all treated dogs ultimately relapse and die due to the residual malignant lymphocytes, namely minimal residual disease (MRD). It would be extremely valuable for clinicians to detect, monitor and quantify MRD for risk group stratification, effective treatment intervention and outcome prediction. The PCRs targeting the Ig gene rearrangements constitute one of the most reliable tools to this end. We have recently validated a method which exploits hairpin-shaped primers for quantifying MRD. In the present study, that method is conveniently used for retrospectively monitoring MRD in the peripheral blood of 8 dogs diagnosed with B-cell lymphoma who underwent chemotherapy. All dogs attained complete remission. The median disease-free interval was 254.5 days (range 63-774) while the median survival time was 313.5 days (range 143-817 days). At admission, all dogs, except one which had already been treated with prednisone, had circulating neoplastic cells. All dogs attained complete remission (CR) which was almost always matched with a complete MRD response. The persistence of MRD despite apparent CR indicated a worse prognosis and a short duration of CR. Finally, the relapse is consistently anticipated by the reappearance of MRD in the peripheral blood. The study confirmed the suitability of an MRD monitoring assay as a clinical decision-making tool.

Minimal residual disease quantification using consensus primers and high-throughput IGH sequencing predicts post-transplant relapse in chronic lymphocytic leukemia

Quantification of minimal residual disease (MRD) following allogeneic hematopoietic cell transplantation (allo-HCT) predicts post-transplant relapse in patients with chronic lymphocytic leukemia (CLL). We utilized an MRD-quantification method that amplifies immunoglobulin heavy chain (IGH) loci using consensus V and J segment primers followed by high-throughput sequencing (HTS), enabling quantification with a detection limit of one CLL cell per million mononuclear cells. Using this IGH–HTS approach, we analyzed MRD patterns in over 400 samples from 40 CLL patients who underwent reduced-intensity allo-HCT. Nine patients relapsed within 12 months post-HCT. Of the 31 patients in remission at 12 months post-HCT, disease-free survival was 86% in patients with MRD <10⁻⁴ and 20% in those with MRD ⩾10⁻⁴ (relapse hazard ratio (HR) 9.0; 95% confidence interval (CI) 2.5–32; P<0.0001), with median follow-up of 36 months. Additionally, MRD predicted relapse at other time points, including 9, 18 and 24 months post-HCT. MRD doubling time <12 months with disease burden ⩾10⁻⁵ was associated with relapse within 12 months of MRD assessment in 50% of patients, and within 24 months in 90% of patients. This IGH–HTS method may facilitate routine MRD quantification in clinical trials.

A single tube 10-color flow cytometry assay optimizes detection of minimal residual disease in chronic lymphocytic leukemia

Levels of residual disease (RD) are an independent predictor of progression-free survival (PFS) and overall survival (OS) in patients treated for chronic lymphocytic leukemia (CLL). We modified the international standardized approach (ISA) to RD detection using flow cytometry by developing a single tube 10 color antibody assay.

METHOD

A single tube incorporated the following monoclonal antibodies: CD81FITC, CD22PE, CD3ECD, CD5PercP5.5, CD20PECY7, CD79bAPC, CD38A700, CD43APC Alexa750, CD19eFluor 450, and CD45KO. A modified ISA gating strategy was developed that removed contaminating events. Sensitivity assays were performed using dilution with normal peripheral blood and bone marrow. Clinical samples were compared using the ISA and the single tube assay.

RESULTS

Dilution studies showed that sensitivity of 0.001% was achievable when a minimum of 1.8 × 10(6) total events were acquired. One hundred twenty-nine samples were analyzed and showed RD levels from 0.003 to 22%. In 80 samples analyzed with both assays, there was an excellent correlation between the two methods (slope = 1.0, intercept = 0.07 and R2 = 0.992) and results from Bland-Altman analysis showed a bias of 0.04 ± 0.38 with 95% confidence interval of -0.71 to 0.79. Removal of contaminating events in the single tube assay led to a significant reduction in RD values (P = 0.0014).

CONCLUSION

The single tube 10-color assay for the detection of RD in CLL provides equivalent results to the ISA but requires fewer cells, uses fewer reagents, and allows for simpler analysis. By directly removing contaminating events, it improves the accuracy of CLL RD detection and may reclassify the status of some patients following chemotherapy.

Flow cytometric MRD detection in selected mature B-cell malignancies

The quantification of submicroscopic minimal residual disease (MRD) after therapy proved to have independent prognostic significance in many mature B-cell malignancies. With the advent of routine bench-top cytometers capable of simultaneously analyzing ≥ 4 colors and with improved standardization, flow cytometry has become the method of choice for MRD assessments in some lymphoma entities. Herein we describe general aspects of flow cytometric standardization. Using chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL) as examples we explain in detail the application of flow cytometry for MRD detection.

A look into the future: can minimal residual disease guide therapy and predict prognosis in chronic lymphocytic leukemia?

Over the past 2 decades, dramatic improvements in the efficacy of treatments for chronic lymphocytic leukemia have led to progressively higher percentages of clinical complete remissions. A molecular eradication of the leukemia has become not only a desirable, but also an achievable, end point that needs to be evaluated within clinical trials. The assessment of complete remission only at the clinical and morphological level is insufficient, at least for physically fit patients. The detection of minimal residual disease (MRD) in chronic lymphocytic leukemia has become feasible using PCR-based or flow cytometric techniques that reproducibly allow reaching the detection level of less than 1 leukemic cell per 10 000 leukocytes (10−4), the level currently defined as MRD− status. Emerging data indicate that the MRD status during and at the end of treatment is one of the most powerful predictors of progression-free and overall survival. This predictor appears to be independent of clinical response, type or line of therapy, and known biological markers. For these reasons, the time is ripe to test the use of MRD as a surrogate marker of clinical end points and as a real-time marker of efficacy and/or resistance to the administered therapies. In the near future, clinical trials will determine whether MRD assessment can be used for guiding therapy, either to improve quality of responses through consolidation or to prevent relapses through preemptive therapies based on the reappearance of MRD.