Adult patients with acute lymphoblastic leukemia and molecular failure display a poor prognosis and are candidates for stem cell transplantation and targeted therapies

New Approaches to the Management of Adult Acute Lymphoblastic Leukemia

Traditional treatment regimens for adult acute lymphoblastic leukemia, including allogeneic hematopoietic cell transplantation, result in an overall survival of approximately 40%, a figure hardly comparable with the extraordinary 80% to 90% cure rate currently reported in children. When translated to the adult setting, modern pediatric-type regimens improve the survival to approximately 60% in young adults. The addition of tyrosine kinase inhibitors for patients with Philadelphia chromosome-positive disease and the measurement of minimal residual disease to guide risk stratification and postremission approaches has led to additional improvements in outcomes. Relapsed disease and treatment toxicity-sparing no patient but representing a major concern especially in the elderly-are the most critical current issues awaiting further therapeutic advancement. Recently, there has been considerable progress in understanding the disease biology, specifically the Philadelphia-like signature, as well as other high-risk subgroups. In addition, there are several new agents that will undoubtedly contribute to additional improvement in the current outcomes. The most promising agents are monoclonal antibodies, immunomodulators, and chimeric antigen receptor T cells, and, to a lesser extent, several new drugs targeting key molecular pathways involved in leukemic cell growth and proliferation. This review examines the evidence supporting the increasing role of the new therapeutic tools and treatment options in different disease subgroups, including frontline and relapsed or refractory disease. It is now possible to define the best individual approach on the basis of the emerging concepts of precision medicine.

[Clinical significance of minimal residual disease in patients with Ph-negative precursor B-acute lymphoblastic leukemia]

Objective: To explore the predictive value of minimal residual disease (MRD) level in Ph-negative precursor B-acute lymphoblastic leukemia (ALL) patients. Methods: De novo 193 Ph-negative B-ALL patients from Sep 2010 to Nov 2017 were involved in the study. The patients' MRD evaluation which can be performed by multiparametric flow cytometry (MFC) after 1 month, 3-month, 6-month treatment. Relapse free survival (RFS) and overall survival (OS) were compared in patients with different MRD level. Results: The median follow-up was 22 months. All patients was evaluated at 497 MRD level. Patients who reach the good MRD level at 1 month (<0.1% or ≥0.1%), 3-month (negative or positive), 6-month (negative or positive) had a significantly higher probability of estimated RFS (74.5% vs 29.9%; 75.6% vs 29.7%; 74.6% vs 11.6%) and of estimated OS (67.5% vs 30.3%; 71.6% vs 27.8%; 74.0% vs 15.7%). Patients who reach the MRD negative at all 3 times had a significantly higher probability of estimated RFS (80.5% vs 30.5%) and better estimated OS (77.1% vs 29.4%) compared to patients with at least MRD failure in one time (P<0.001). Multivariable analysis showed MRD level at 3-month was an independent prognostic factor for DFS and OS. Conclusion: MRD is an important prognosis factor for Ph-negative B- ALL patients.

Intensified Therapy of Acute Lymphoblastic Leukemia in Adults: Report of the Randomized GRAALL-2005 Clinical Trial

Purpose

To evaluate randomly the role of hyperfractionated cyclophosphamide (hyper-C) dose intensification in adults with newly diagnosed Philadelphia chromosome–negative acute lymphoblastic leukemia treated with a pediatric-inspired protocol and to determine the upper age limit for treatment tolerability in this context.

Patients and Methods

A total of 787 evaluable patients (B/T lineage, 525 and 262, respectively; median age, 36.1 years) were randomly assigned to receive a standard dose of cyclophosphamide or hyper-C during first induction and late intensification. Compliance with chemotherapy was assessed by median doses actually received during each treatment phase by patients potentially exposed to the full planned doses.

Results

Overall complete remission (CR) rate was 91.9%. With a median follow-up of 5.2 years, the 5-year rate of event-free survival (EFS) and overall survival (OS) was 52.2% (95% CI, 48.5% to 55.7%) and 58.5% (95% CI, 54.8% to 61.9%), respectively. Randomization to the hyper-C arm did not increase the CR rate or prolong EFS or OS. As a result of worse treatment tolerance, advanced age continuously affected CR rate, EFS, and OS, with 55 years as the best age cutoff. At 5 years, EFS was 55.7% (95% CI, 51.8% to 59.4%) for patients younger than 55 years of age versus 25.8% (95% CI, 19.9% to 35.6%) in older patients (hazard ratio, 2.16; P < .001). Patients ≥ 55 years of age, in whom a lower compliance to the whole planned chemotherapy was observed, benefited significantly from hyper-C, whereas younger patients did not.

Conclusion

No significant benefit was associated with the introduction of a hyper-C sequence into a frontline pediatric-like adult acute lymphoblastic leukemia therapy. Overall, tolerability of an intensive pediatric-derived treatment was poor in patients ≥ 55 years of age.

Reduced Intensity Conditioning Allogeneic Hematopoietic Stem Cell Transplantation for Acute Lymphoblastic Leukemia; Current Evidence, and Improving Outcomes Going Forward

PURPOSE OF REVIEW

Outcomes for older adults with acute lymphoblastic leukemia (ALL) remain poor, and allogeneic hematopoietic stem cell transplant (HSCT) remains a potentially curative modality. However, benefits are offset by high rates of non-relapse mortality (NRM) in patients undergoing myeloablative conditioning (MAC) regimens. Reduced intensity conditioning (RIC) regimens can extend this therapy to adults who are unfit for MAC, although at the cost of higher relapse rates. In this review, we discuss evidence to support the usage of RIC regimens, controversies, and potential strategies to improve transplant outcomes going forward.

RECENT FINDINGS

Several novel therapies have recently been approved for the treatment of relapsed ALL and may play an important role in bridging adults with residual disease to RIC transplant. Assessing response to initial therapy via minimal residual disease (MRD) monitoring may determine which patients will derive the most benefit from allogeneic HSCT. Reduced intensity allogeneic HSCT remains a potentially curative therapy that can be offered to older adults however challenges remain. Going forward, MRD testing and novel therapies may help better select which patients should proceed to transplant and assist in getting those patients to transplant with optimally controlled disease.

Description and prognostic significance of the kinetics of minimal residual disease status in adults with acute lymphoblastic leukemia treated with HyperCVAD

HyperCVAD is a commonly-used regimen for adults with newly-diagnosed acute lymphoblastic leukemia (ALL). However, relatively little is known about the application of minimal residual disease (MRD) detection with this treatment. To address this, we studied 142 adults with ALL treated with hyperCVAD over a 10-year period who had MRD assessed by either multi-parameter flow cytometry or (for patients with Philadelphia chromosome positive ALL) reverse transcriptase polymerase chain reaction for the BCR-ABL1 translocation. In a multivariate analysis, patients who achieved MRD negativity (MRD^Neg ) at any point had significantly better overall survival (OS; hazard ratio [HR] 0.43; P = .01) and event-free survival (EFS; HR 0.27; P < .01). Of 121 patients with MRD assessed at various points within 90 days of starting hyperCVAD, 50% (n = 61) had achieved MRD^Neg . Among those that became MRD^Neg , the median time to MRD^Neg was 68 days. Time to MRD^Neg was significantly associated with EFS (P = .009), but not OS (P = .19), implying increasingly better EFS the earlier MRD^Neg is achieved. These data add to our understanding of MRD assessment during treatment with hyperCVAD, aide clinicians with predicting relapse risk, and provide additional historical data on which future clinical trials can be designed.

Comparison of Real-time Quantitative Polymerase Chain Reaction and Eight-color Flow Cytometry in Assessment of Minimal Residual Disease in Adult Acute Lymphoblastic Leukemia

BACKGROUND

Minimal residual disease (MRD) is an important prognostic maker in acute lymphoblastic leukemia (ALL). However, few data comparing the measurement of adult ALL MRD using different methods in daily practice are available. We conducted an analysis comparing the importance of flow cytometry (FCM) and real-time quantitative polymerase chain reaction (PCR) in the assessment of MRD in adult ALL.

PATIENTS AND METHODS

Fifty-six consecutive adult patients with both Philadelphia-negative and -positive ALL treated according to an intensive protocol were enrolled in the study. Bone marrow samples were acquired on day 26 and during week 11 of treatment. MRD evaluation was performed using 8-color FCM and PCR of immunoglobulin or T-cell receptor gene clonal rearrangements and BCR-ABL1, KMT2A-AF4 and E2A-PBX1 fusion genes.

RESULTS

On day 26, both FCM and PCR seemed to have good discrimination sensitivity for overall survival (P = .001 to .008) and progression-free survival (P = .03 to .04) prediction for both Philadelphia-positive and -negative cases. The most sensitive method in week 11 was PCR including all results > 0 considered to indicate MRD positivity (P = .002 for overall survival and P = .02 for progression-free survival). PCR with other cutoffs was not sufficiently sensitive in week 11. Moreover, no FCM⁺ samples were found in week 11. The subanalysis of the Philadelphia-negative patients showed similar results.

CONCLUSION

Our analysis showed that both FCM and PCR MRD assessment methods are sensitive for survival prediction during induction. However, we believe FCM could not be sufficiently sensitive in later phases of treatment.

Acute lymphoblastic leukemia in adolescent and young adults: treat as adults or as children?

Adolescent and young adult (AYA) patients with acute lymphoblastic leukemia (ALL) are recognized as a unique population with specific characteristics and needs. In adolescents age 15 to 20 years, the use of fully pediatric protocols is supported by many comparative studies of pediatric and adult cooperative groups. In young adults, growing evidence suggests that pediatric-inspired or even fully pediatric approaches may also dramatically improve outcomes, leading to long-term survival rates of almost 70%, despite diminishing indications of hematopoietic stem-cell transplantation. In the last decade, better knowledge of the ALL oncogenic landscape according to age distribution and minimal residual disease assessments has improved risk stratification. New targets have emerged, mostly in the heterogeneous B-other group, particularly in the Philadelphia-like ALL subgroup, which requires both in-depth molecular investigations and specific evaluations of targeted treatments. The remaining gap in the excellent results reported in children has many other contributing factors that should not be underestimated, including late or difficult access to care and/or trials, increased acute toxicities, and poor adherence to treatment. Specific programs should be designed to take into account those factors and finally ameliorate survival and quality of life for AYAs with ALL.

Blast Percentage of Bone Marrow Aspirate on Day 14 of Induction Chemotherapy Predicts Adult Acute Lymphoblastic Leukemia Treatment Outcomes

The prognosis of adult acute lymphoblastic leukemia is much worse than that of pediatric acute lymphoblastic leukemia, even when patients achieve complete remission. Early response to treatment can be an important alternative indicator of treatment outcomes. The purpose of our current study was to identify the prognostic value of the blast percentage of the induction interim bone marrow, which might predict relapse-free survival and overall survival in patients with adult acute lymphoblastic leukemia. A retrospective analysis was performed on 80 adult patients diagnosed with Philadelphia chromosome-negative acute lymphoblastic leukemia from 1994 to 2011. Complete remission was observed in 75 (93.8%) patients after induction chemotherapy. On multivariate analysis, a reduction of blasts to a level of 5% or less in the induction interim bone marrow and CD20 positivity were significant prognostic predictors of relapse-free survival (hazard ratio, HR = 2.88, p = 0.006, and HR = 2.67, p = 0.010) and overall survival (HR = 2.10, p = 0.033, and HR = 2.39, p = 0.013). The blast percentage of the induction interim bone marrow may be a useful prognostic factor to predict outcome.

Minimal Residual Disease Assessment and Risk-based Therapy in Acute Lymphoblastic Leukemia

The study of minimal residual disease (MRD) in adult patients with acute lymphoblastic leukemia (ALL) allows a greater refinement of the individual risk classification and is the best support for risk-specific therapy with or without allogeneic hematopoietic cell transplantation (HCT). Using case-specific sensitive molecular probes or multiparametric flow cytometry on marrow samples obtained from the end of induction until midconsolidation, MRD assays can detect up to 1 leukemic cell of 10,000 total mononuclear cells (sensitivity, 0.01%; ie, ≥10⁴). This cutoff, presently bound to technical limitations and subject to improvement, reflects the individual chemosensitivity and is strongly correlated with treatment outcome. The chance for cure is approximately 70% in the MRD-negative subset but only 20% to 30% in MRD-positive patients, in any diagnostic and risk subset. As shown by prospective trials from Germany, Italy, Spain, and France-Switzerland-Belgium, approximately 50% to 70% of unselected adult patients with Philadelphia-negative ALL achieve and maintain an early MRD response, whereas the remainder do not, including a substantial proportion of clinically standard-risk patients, and require an HCT to avert at least partially the risk of relapse. Along with the diffusion of more effective "pediatric-inspired" chemotherapy programs, the MRD analysis is an integral part of a modern management strategy, guiding the decision process to transplant or not, in which case nonrelapse mortality using HCT in first remission-still 10% to 20%-is totally abolished. The use of new agents such as monoclonal antibodies, small inhibitors, and chimeric antigen receptor T cells is opening a new era of MRD-directed therapies, that will further increase survival rates.

Prolonged Survival of Acute Lymphoblastic Leukemia with Intrathecal Treatments for Isolated Central Nervous System Relapse

Acute lymphoblastic leukemia is commonly cured when diagnosed in the pediatric population. It portends a poorer prognosis if present in adult patients. Although adults frequently achieve complete remission, relapse rates are substantial, particularly among the elderly and high-risk populations. In the absence of prophylactic intrathecal chemotherapy, more than half of patients may develop CNS involvement or relapse, which is associated with significant risk for systemic illness. This report describes a patient with acute lymphoblastic leukemia with repeated isolated CNS relapses. This case should remind clinicians that isolated CNS disease in the absence of systemic recurrence could successfully respond to intrathecal therapy and offer patients a favorable quality of life.

"Society of Hematologic Oncology (SOHO) State of the Art Updates and Next Questions"-Treatment of ALL

The outcome of adult acute lymphoblastic leukemia (ALL) has substantially improved by adopting pediatric-inspired regimens, and approximately half of the patients are nowadays cured. The evaluation of minimal residual disease currently represents the most important prognostic indicator, which drives treatment algorithms, which include allogeneic stem cell transplantation (allo-SCT) allocation. Indeed, for high-risk patients, allo-SCT should be pursued as soon as possible, whereas in standard-risk patients this procedure should be avoided also in light of related toxicity and because there are no significant benefits. Furthermore, better characterization of the molecular genetic events can drive therapeutic decisions: a historical example in this respect is represented by the use of tyrosine kinase inhibitors (TKIs) in Philadelphia chromosome-positive ALL; in the upcoming future, TKIs might be used also in other subgroups, such as breakpoint cluster region/Abelson 1-like cases and others with deregulated tyrosine kinases. Finally, the greatest progress is currently achieved with new immunotherapies targeting frequently expressed surface antigens in ALL. It is also a new chance for elderly ALL patients, so far spared from intensive chemotherapy and allo-SCT. These targeted therapies will substantially change this treatment algorithm and the great challenge is to find optimal sequence of the extended therapy options in an individual patient.

Targeting minimal residual disease: a path to cure?

Therapeutics that block kinases, transcriptional modifiers, immune checkpoints and other biological vulnerabilities are transforming cancer treatment. As a result, many patients achieve dramatic responses, including complete radiographical or pathological remission, yet retain minimal residual disease (MRD), which results in relapse. New functional approaches can characterize clonal heterogeneity and predict therapeutic sensitivity of MRD at a single-cell level. Preliminary evidence suggests that iterative detection, profiling and targeting of MRD would meaningfully improve outcomes and may even lead to cure.

Efficacy of Ponatinib Versus Earlier Generation Tyrosine Kinase Inhibitors for Front-line Treatment of Newly Diagnosed Philadelphia-positive Acute Lymphoblastic Leukemia

INTRODUCTION

Complete molecular response (CMR) and 2- and 3-year overall survival (OS) were compared for patients with newly diagnosed Philadelphia-positive acute lymphoblastic leukemia (Ph+ ALL) who had undergone front-line combination chemotherapy plus ponatinib versus combination therapy plus earlier generation tyrosine kinase inhibitors (TKIs; imatinib, dasatinib, and nilotinib).

PATIENTS AND METHODS

We identified 26 Ph+ ALL studies: 25 of earlier generation TKIs and 1 of ponatinib. The outcomes from studies of combination chemotherapy plus earlier generation TKIs were summarized using pooled estimates with 95% confidence intervals (CIs) from a random-effects meta-analysis. A binomial distribution was assumed to calculate the 95% CIs for the results from the single-arm combination chemotherapy plus ponatinib trial. Adjusted logistic meta-regression analyses were used to compare the outcomes between the TKI groups.

RESULTS

The percentage of patients achieving a CMR was greater with combination chemotherapy plus ponatinib (79%) than the pooled percentage of patients achieving a CMR with combination chemotherapy plus earlier generation TKIs (34%). Greater OS was observed with ponatinib compared with the pooled OS for earlier generation TKIs (2-year, 83% vs. 58%; 3-year, 79% vs. 50%). Odds ratios for ponatinib versus earlier generation TKIs were 6.09 (95% CI, 1.16-31.90; P = .034) for CMR, 3.70 (95% CI, 0.93-14.73; P = .062) for 2-year OS, and 4.49 (95% CI, 1.00-20.13; P = .050) for 3-year OS.

CONCLUSION

Ponatinib plus chemotherapy might be associated with better outcomes than chemotherapy with earlier generation TKIs in patients with newly diagnosed Ph+ ALL.

Flow cytometric minimal residual disease assessment of peripheral blood in acute lymphoblastic leukaemia patients has potential for early detection of relapsed extramedullary disease

OBJECTIVES

To evaluate peripheral blood (PB) for minimal residual disease (MRD) assessment in adults with acute lymphoblastic leukaemia (ALL).

METHODS

We analysed 76 matched bone marrow (BM) aspirate and PB specimens independently for the presence of ALL MRD by six-colour flow cytometry (FC).

RESULTS

The overall rate of BM MRD-positivity was 24% (18/76) and PB was also MRD-positive in 22% (4/18) of BM-positive cases. We identified two cases with evidence of leukaemic cells in PB at the time of the extramedullary relapse that were interpreted as MRD-negative in BM.

CONCLUSIONS

The use of PB MRD as a non-invasive method for monitoring of systemic relapse may have added clinical and diagnostic value in patients with high risk of extramedullary disease.

Hematopoietic Stem Cell Transplantation for Adult Philadelphia-Negative Acute Lymphoblastic Leukemia in the First Complete Remission in the Era of Minimal Residual Disease

PURPOSE OF REVIEW

The purpose of this review is to discuss the potential role of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for Philadelphia-negative (Ph^-) adult acute lymphoblastic leukemia (ALL) in first complete remission (CR1) in the era of minimal residual disease (MRD).

RECENT FINDINGS

Allo-HSCT continues to have a role in the therapy of a selected group of high-risk adult patients with ALL in CR1. Although the clinical significance of MRD has been studied less extensively in adults with ALL than in children, recent studies support its role as the strongest prognostic factor that can identify patients that are unlikely to be cured by standard chemotherapy and benefit from undergoing allo-HSCT. In addition, MRD status both pre- and post-HSCT has been found to correlate directly with the risk of relapse. Currently, the clinical challenge consists on applying MRD and molecular failure to integrate novel agents and immunotherapy to lower MRD before allo-HSCT and to modulate the graft versus leukemia (GVL) effect after transplant.

Hematopoietic stem cell transplant in adults with acute lymphoblastic leukemia: the present state

INTRODUCTION

Allogeneic hematopoietic stem cell transplant (allo-HSCT) has an important role in management of acute lymphoblastic leukemia (ALL). Proper patient selection is central to ensure optimal outcomes. Areas covered: This review covers various aspects of HSCT in ALL patients, including indications, donor selection, conditioning regimens, and post-transplant management. Expert commentary: Allo-HSCT is important in post-remission management of ALL but proper risk-stratification is a major challenge. Incorporation of minimal residual disease (MRD) and molecular testing will improve patient allocation. Patients receiving pediatric-inspired induction who achieve molecular remission might not need allo-HSCT in first remission. Allo-HSCT should be considered in patients who don't achieve MDR negativity, didn't receive intensive induction, or have high risk cytogenetic and molecular features. Despite improved responses with tyrosine kinase inhibitors (TKIs) in Philadelphia positive (Ph+) ALL, allo-HSCT remains standard. Matched sibling donors are the optimal graft source, but other sources are valid alternatives. There is no single optimal conditioning regimen and retrospective studies found myeloablative and reduced intensity regimens to be comparable. Following allo-HSCT, there is no role for maintenance therapy in Philadelphia-negative ALL. In Ph+ ALL, maintenance TKIs improve outcomes. The integration of targeted and immunotherapies in the peri-transplant period holds potential for improved outcomes.

Minimal residual disease (MRD) detection using rearrangement of immunoglobulin/T cell receptor genes in adult patients with acute lymphoblastic leukemia (ALL)

MRD detection with allele-specific oligonucleotide-quantitative polymerase chain reaction (ASO-qPCR) and using clone-specific immunoglobulin/T cell receptor rearrangements is considered as a powerful prognostic factor in acute lymphoblastic leukemia (ALL). In the present study, we evaluated an ASO-qPCR assay for MRD quantification in peripheral blood (PB) samples of adult patients with ALL. DNA was isolated from PB samples of patients with newly diagnosed ALL. They were first investigated by multiplex-PCR assay to identify V/J usage. An ASO-qPCR technique was then applied for 2.5-year monthly MRD quantification for detection of patient-specific Ig/TCR receptor rearrangements as a molecular target. From 98 patients who were diagnosed as ALL, 72 (73.5%) were enrolled in the present study for MRD detection. MRD was successfully quantified in patients with 1-month interval time. MRD level at the end of induction therapy up to day 88 was the only significant prognostic factor. Regarding MRD level, patients were categorized into two groups of low and high-risk. 2.5-year OS in all three time points (days 28, 58 and 88) were significantly lower in high-risk group (P < 0.008). The results of the 2.5-year MRD detection indicate that MRD level at the end of induction up to about 6 months after the first diagnosis was associated with clinical outcome. This study may highlight the usefulness of PB and the definitions of cut-off level for early prediction of relapse and for stratifying ALL patients. Short-interval time points and frequent PB sampling to monitor MRD level is suggested for early clinical relapse prediction and clinical management of the disease.

Blinatumomab for minimal residual disease in adults with B-cell precursor acute lymphoblastic leukemia

Approximately 30% to 50% of adults with acute lymphoblastic leukemia (ALL) in hematologic complete remission after multiagent therapy exhibit minimal residual disease (MRD) by reverse transcriptase-polymerase chain reaction or flow cytometry. MRD is the strongest predictor of relapse in ALL. In this open-label, single-arm study, adults with B-cell precursor ALL in hematologic complete remission with MRD (≥10^-3) received blinatumomab 15 µg/m² per day by continuous IV infusion for up to 4 cycles. Patients could undergo allogeneic hematopoietic stem-cell transplantation any time after cycle 1. The primary end point was complete MRD response status after 1 cycle of blinatumomab. One hundred sixteen patients received blinatumomab. Eighty-eight (78%) of 113 evaluable patients achieved a complete MRD response. In the subgroup of 110 patients with Ph-negative ALL in hematologic remission, the Kaplan-Meier estimate of relapse-free survival (RFS) at 18 months was 54%. Median overall survival (OS) was 36.5 months. In landmark analyses, complete MRD responders had longer RFS (23.6 vs 5.7 months; P = .002) and OS (38.9 vs 12.5 months; P = .002) compared with MRD nonresponders. Adverse events were consistent with previous studies of blinatumomab. Twelve (10%) and 3 patients (3%) had grade 3 or 4 neurologic events, respectively. Four patients (3%) had cytokine release syndrome grade 1, n = 2; grade 3, n = 2), all during cycle 1. After treatment with blinatumomab in a population of patients with MRD-positive B-cell precursor ALL, a majority achieved a complete MRD response, which was associated with significantly longer RFS and OS compared with MRD nonresponders. This study is registered at www.clinicaltrials.gov as #NCT01207388.

Minimal residual disease in adult ALL: technical aspects and implications for correct clinical interpretation

Nowadays, minimal residual disease (MRD) is accepted as the strongest independent prognostic factor in acute lymphoblastic leukemia (ALL). It can be detected by molecular methods that use leukemia-specific or patient-specific molecular markers (fusion gene transcripts, or immunoglobulin/T-cell receptor [IG/TR] gene rearrangements), and by multi-parametric flow cytometry. The sensitivity and specificity of these methods can vary across treatment time points and therapeutic settings. Thus, knowledge of the principles and limitations of each technology is of the utmost importance for correct interpretation of MRD results. Time will tell whether new molecular and flow cytometric high-throughput technologies can overcome the limitations of current standard methods and eventually bring additional benefits. MRD during standard ALL chemotherapy is the strongest overall prognostic indicator and has therefore been used for refining initial treatment stratification. Moreover, MRD positivity after the maintenance phase of treatment may point to an impending relapse and thus enable salvage treatment to be initiated earlier, which could possibly improve treatment results. The prognostic relevance of pretransplantation MRD was shown by several studies, and MRD high-risk patients were shown to benefit from stem cell transplantation (SCT). Also, MRD positivity after SCT correlates with worse outcomes. In addition, MRD information is very instructive in current clinical trials that test novel agents to evaluate their treatment efficacy. Although conventional clinical risk factors lose their independent prognostic significance when combined with MRD information, recently identified genetic markers may further improve the treatment stratification in ALL.

Minimal residual disease in adult ALL: technical aspects and implications for correct clinical interpretation

Nowadays, minimal residual disease (MRD) is accepted as the strongest independent prognostic factor in acute lymphoblastic leukemia (ALL). It can be detected by molecular methods that use leukemia-specific or patient-specific molecular markers (fusion gene transcripts, or immunoglobulin/T-cell receptor [IG/TR] gene rearrangements), and by multi-parametric flow cytometry. The sensitivity and specificity of these methods can vary across treatment time points and therapeutic settings. Thus, knowledge of the principles and limitations of each technology is of the utmost importance for correct interpretation of MRD results. Time will tell whether new molecular and flow cytometric high-throughput technologies can overcome the limitations of current standard methods and eventually bring additional benefits. MRD during standard ALL chemotherapy is the strongest overall prognostic indicator and has therefore been used for refining initial treatment stratification. Moreover, MRD positivity after the maintenance phase of treatment may point to an impending relapse and thus enable salvage treatment to be initiated earlier, which could possibly improve treatment results. The prognostic relevance of pretransplantation MRD was shown by several studies, and MRD high-risk patients were shown to benefit from stem cell transplantation (SCT). Also, MRD positivity after SCT correlates with worse outcomes. In addition, MRD information is very instructive in current clinical trials that test novel agents to evaluate their treatment efficacy. Although conventional clinical risk factors lose their independent prognostic significance when combined with MRD information, recently identified genetic markers may further improve the treatment stratification in ALL.

Relapsed acute lymphoblastic leukemia: Is it crucial to achieve molecular remission prior to transplant?

In patients with acute lymphoblastic leukemia (ALL) the risk of recurrent leukemia influences the choice of treatment between chemotherapy and allogeneic hematopoietic cell transplantation. The evaluation of minimal residual disease (MRD) is now considered to be the greatest progress in risk stratification in regard to leukemia recurrence. Achieving molecular remission at the end of induction therapy after diagnosis or after relapse has influenced treatment choice. Failure to achieve molecular remission is considered "high risk" and allogeneic hematopoietic cell transplantation with a suitable donor, the accepted standard. Nevertheless, published reports support lower relapse and higher survival rates for those in molecular remission at transplantation compared to those in morphological remission. In the setting of relapsed ALL, the availability of targeted therapies offers an opportunity for molecular remission so that transplant recipients have the best possible option of attaining sustained remission upon completion of this treatment.

Current challenges and opportunities in treating adult patients with Philadelphia-negative acute lymphoblastic leukaemia

Significant advances have been made in recent years in the field of Philadelphia-negative acute lymphoblastic leukaemia (ALL). New insights into the biology and genetics of ALL as well as novel clinical observations and new drugs are changing the way we diagnose, risk-stratify and treat adult patients with ALL. New genetic subtypes and alterations refine risk stratification and uncover new actionable therapeutic targets. The incorporation of more intensive, paediatric and paediatric-inspired approaches for young adults seem to have a positive impact on survival in this population. Minimal residual disease at different time points can assist in tailoring risk-adapted interventions for patients based on individual response. Finally, novel targeted approaches with monoclonal antibodies, immunotherapies and small molecules are moving through clinical development and entering the clinic. The aim of this review is to consolidate the abundance of emerging data and to review and revisit the concepts of risk-stratification, choice of induction and post-remission strategies as well as to discuss and update the approach to specific populations with ALL, such as young adult, elderly/unfit and relapsed/refractory patients with ALL.

An update on PCR use for minimal residual disease monitoring in acute lymphoblastic leukemia

INTRODUCTION

Acute lymphoblastic leukemia (ALL) is the first neoplasm where the assessment of early response to therapy by minimal residual disease (MRD) monitoring has proven to be a fundamental tool for guiding therapeutic choices. In recent years, thanks to real-time quantitative PCR (qPCR), MRD monitoring has further achieved higher levels of sensitivity and standardization. However, some outstanding issues still remain to be addressed and emerging technologies hold the promise of improving MRD detection in ALL patients. Areas covered: Through a comprehensive review of the literature, we analyze the state-of-the-art of molecular MRD assessment in ALL to better understand how, in the upcoming years, some of its limitations could be tackled by emerging molecular technologies. Furthermore, we highlight the future role of molecular MRD monitoring in the context of personalized protocols, taking into account the growing genetic complexity in ALL. Expert commentary: Although new molecular technologies are promising tools for MRD assessment, qPCR still remains the gold standard for evaluating MRD in ALL. High-throughput sequencing and droplet digital PCR allow to identify new prognostic factors and/or MRD targets at diagnosis and to perform earlier MRD evaluations, thereby optimizing patient stratification and earlier MRD-based clinical intervention to improve ALL patient outcomes.

Redefining treatment failure for pediatric acute leukemia in the era of minimal residual disease testing

Technologies for the detection of minimal residual disease (MRD) in leukemia and our understanding of the prognostic implications of MRD at different phases of treatment have significantly improved over the past decade. As a result, definitions of treatment failure based on bone marrow morphology by light microscopy are becoming increasingly inadequate for clinical care and trial design. In addition, novel therapies that may have increased efficacy and decreased toxicity in the setting of MRD compared to overt disease are changing clinical practice and challenging investigators to redefine treatment failure, the role of disease surveillance in remission, and clinical trial eligibility in the era of MRD.

Clinical applications and safety evaluation of the new CD19 specific T-cell engager antibody construct blinatumomab

INTRODUCTION

Blinatumomab is a T-cell engager antibody construct with dual specificity for CD19 and CD3, inducing serial lysis of CD19 positive B cells by redirecting cytotoxic T cells. It has been approved for the indication of Ph chromosome negative relapsed or refractory B-acute lymphoblastic leukemia (ALL), but has also been tested in ALL with minimal residual disease, relapsed Ph/BCR-ABL positive ALL, relapsed ALL in pediatric patients and relapsed or refractory non-Hodgkin's lymphoma (NHL). Adverse events have been mainly related to infection and hematological toxicities, as well as cytokine release syndrome and neurotoxicity. Areas covered: The review will discuss mechanisms of action, published literature on efficacy in ALL and NHL, specific aspects of administration, frequent adverse events and practical management. Expert opinion: Blinatumomab represents an effective new treatment for highly resistant relapsed/refractory B-precursor ALL. Practical handling bears challenges due to application as four week continous infusion and specific adverse effects which can be well handled by experienced centers. Most promising outcomes are reported for patients with resistant disease but lower tumor load such as MRD positive ALL patients. Future studies will focus on the use of blinatumomab during first-line therapy and the role of stem cell transplantation after blinatumomab treatment.

[Adult B-cell acute lymphoblastic leukemias: Conclusions of the Russian prospective multicenter study ALL-2009]

AIM

To analyze the efficiency and reproducibility of the ALL-2009 protocol within the Russian prospective multicenter study based on different principles of cytostatic effects (non-intensive, but continuous cytotoxic treatment and a small number of allogeneic hematopoietic stem cells).

SUBJECTS AND METHODS

The ALL-2009 (NCT01193933) study conducted in April 2009 to December 2016 included 194 patients (95 males and 99 females) aged 15 to 55 years (median age 28 years) with Ph-negative B-cell acute lymphoblastic leukemia (ALL). There was early pre-B-cell ALL in 54 patients, common ALL in 101, pre-B ALL in 39, initial leukocytosis in 9.4·109/l (0.4-899.0), lactate dehydrogenase in 901 IU (31-13 059), an initial central nervous system lesion in 17 (8.7%), mediastinal injury in 3 (1.5%), and splenomegaly in 111 (57.2%). The results of standard cytogenetic analysis are known in 113 (60.4%) patients. Normal karyotypes were detected in 49 (54.5%) out of the patients; t(4;11) in 9 (5.4%), t(1;19) in 2 (1.2%), and other karyotypic abnormalities in 53 (46.9%). Thirteen (7.8%) patients underwent allogeneic hematopoietic stem cell transplantation in first complete remission (CR); their proportion did not differ in the federal and regional centers.

RESULTS

The frequency of CR achievement was the same in the federal and regional centers and generally amounted to 87.5%. Early (8.8%) and CR (9.6%) mortality rates remained high despite the low aggressiveness of cytotoxic action, necessitating the improvement of auxiliary treatment. The five-year overall survival (OS) rates vary considerably in the federal and regional centers (72.6 and 43.8%), the relapse-free survival (RFS) (70.2 and 53.4%) and recurrence risk (23.1 and 36.5%) are comparable. This suggests that the non-intensive, but continuous exposure principle built in the ALL-2009 protocol makes it possible to reproduce the envisaged treatment program and to achieve satisfactory results.

CONCLUSION

The ALL-2009 protocol allows both the federal and regional centers to obtain the long-term results comparable with those of current foreign studies: OS (54.2%), RFS (56.5%); and relapse risk (35.4%). Multivariate analysis has identified age (over 30 years), initial leukocytosis (30·109/l and more) and t(4;11) among the main clinical prognostic factors. Gene mutation detection evaluated in a small number of patients (8/36) is not a poor prognostic sign. There is a need for further investigations with centralized evaluation of the mutation status of leukemic cells and the clearance of minimal residual disease.

How should we treat the AYA patient with newly diagnosed ALL?

Adolescent and young adult (AYA) patients with acute lymphoblastic leukaemia (ALL) are recognized as a unique population with specific characteristics and needs. In adolescents aged 15-20 years old, the use of full paediatric protocols is supported by many comparative studies of paediatric and adult cooperative groups. In young adults, growing evidence suggests that paediatric-inspired approaches may also improve outcomes and lead to long-term survival rates of almost 70%. In the last decade, better knowledge of ALL oncogenic landscape, age distribution, and minimal residual disease prognostic impact have improved risk stratification. New targets have emerged mostly in the heterogeneous subgroup of Philadelphia-like ALL and will require both in-depth molecular investigations and specific evaluations in rare subgroups of ALL. The remaining gap with the excellent results reported in children has many other contributing factors that should not be underestimated including late or difficult access to care, or poor adherence to treatment.

How should we treat a patient with relapsed Ph-negative B-ALL and what novel approaches are being investigated?

Despite significant improvements in outcome of newly diagnosed B-precursor ALL, the results in relapsed or refractory adult ALL are overall poor. Large retrospective studies revealed significant differences in terms of outcome, with particularly poor response rates in early or refractory relapses, whereas late relapses usually respond very well to repeated standard induction. Particularly new immunotherapy compounds like the CD19 bispecific antibody Blinatumomab and the conjugated CD22 antibody Inotuzumab yielded promising response rates compared to standard therapies in randomised trials. Long-term survival is however still poor. The optimal use of these compounds remains to be defined. Chimeric antigen receptor T-cells are another promising treatment approach and multicenter clinical trials in adult ALL are awaited. For selected patients molecular directed therapies may have a role in relapsed ALL; standard diagnostic algorithms need to be defined. One of the major challenges is to define the role of stem cell transplantation after relapse. Whereas this procedure appears to be the only chance for cure, the mortality and relapse rate are still high and optimisation is urgently needed. Future strategies include optimised use of new compounds as part of combination regimens and the earlier treatment of upcoming relapse in the situation of persistent or recurrent minimal residual disease.

Association of Minimal Residual Disease With Clinical Outcome in Pediatric and Adult Acute Lymphoblastic Leukemia: A Meta-analysis

Importance

Minimal residual disease (MRD) refers to the presence of disease in cases deemed to be in complete remission by conventional pathologic analysis. Assessing the association of MRD status following induction therapy in patients with acute lymphoblastic leukemia (ALL) with relapse and mortality may improve the efficiency of clinical trials and accelerate drug development.

Objective

To quantify the relationships between event-free survival (EFS) and overall survival (OS) with MRD status in pediatric and adult ALL using publications of clinical trials and other databases.

Data Sources

Clinical studies in ALL identified via searches of PubMed, MEDLINE, and clinicaltrials.gov.

Study Selection

Our search and study screening process adhered to the PRISMA Guidelines. Studies that addressed EFS or OS by MRD status in patients with ALL were included; reviews, abstracts, and studies with fewer than 30 patients or insufficient MRD description were excluded.

Data Extraction and Synthesis

Study sample size, patient age, follow-up time, timing of MRD assessment (postinduction or consolidation), MRD detection method, phenotype/genotype (B cell, T cell, Philadelphia chromosome), and EFS and OS. Searches of PubMed and MEDLINE identified 566 articles. A parallel search on clinicaltrials.gov found 67 closed trials and 62 open trials as of 2014. Merging results of 2 independent searches and applying exclusions gave 39 publications in 3 arms of patient populations (adult, pediatric, and mixed). We performed separate meta-analyses for each of these 3 subpopulations.

Results

The 39 publications comprised 13 637 patients: 16 adult studies (2076 patients), 20 pediatric (11 249 patients), and 3 mixed (312 patients). The EFS hazard ratio (HR) for achieving MRD negativity is 0.23 (95% Bayesian credible interval [BCI] 0.18-0.28) for pediatric patients and 0.28 (95% BCI, 0.24-0.33) for adults. The respective HRs in OS are 0.28 (95% BCI, 0.19-0.41) and 0.28 (95% BCI, 0.20-0.39). The effect was similar across all subgroups and covariates.

Conclusions and Relevance

The value of having achieved MRD negativity is substantial in both pediatric and adult patients with ALL. These results are consistent across therapies, methods of and times of MRD assessment, cutoff levels, and disease subtypes. Minimal residual disease status warrants consideration as an early measure of disease response for evaluating new therapies, improving the efficiency of clinical trials, accelerating drug development, and for regulatory approval. A caveat is that an accelerated approval of a particular new drug using an intermediate end point, such as MRD, would require confirmation using traditional efficacy end points.

Acute lymphoblastic leukemia: a comprehensive review and 2017 update

Acute lymphoblastic leukemia (ALL) is the second most common acute leukemia in adults, with an incidence of over 6500 cases per year in the United States alone. The hallmark of ALL is chromosomal abnormalities and genetic alterations involved in differentiation and proliferation of lymphoid precursor cells. In adults, 75% of cases develop from precursors of the B-cell lineage, with the remainder of cases consisting of malignant T-cell precursors. Traditionally, risk stratification has been based on clinical factors such age, white blood cell count and response to chemotherapy; however, the identification of recurrent genetic alterations has helped refine individual prognosis and guide management. Despite advances in management, the backbone of therapy remains multi-agent chemotherapy with vincristine, corticosteroids and an anthracycline with allogeneic stem cell transplantation for eligible candidates. Elderly patients are often unable to tolerate such regimens and carry a particularly poor prognosis. Here, we review the major recent advances in the treatment of ALL.

Continuing challenges and current issues in acute lymphoblastic leukemia

Conventional cytotoxic chemotherapy used to treat acute lymphoblastic leukemia (ALL) has resulted into high cure rates for pediatric patients, however outcomes for adult patients remain suboptimal. The 5-year overall survival is only 30-40% in adults and elderly patients with ALL compared to 90% in children. We have seen major advances in our understanding and management of ALL related to identification of new cytogenetic and molecular abnormalities and development of novel targeted agents for the treatment of ALL. The addition of tyrosine kinase inhibitors, monoclonal antibodies and novel immune therapies (e.g. bispecific T cell engager [BiTE] and chimeric antigen receptor [CAR] T cells) has resulted in improved outcomes. These new developments are changing the treatment paradigm of adults ALL from a 'one size fits all' approach to a more individualized treatment approach based on immunophenotypic, cytogenetic and molecular features. In this article we review recent diagnostic and therapeutic advances along with the challenges in the treatment of patients with ALL.