Influence of pre-transplant minimal residual disease on prognosis after Allo-SCT for patients with acute lymphoblastic leukemia: systematic review and meta-analysis

Clinical use of measurable residual disease in adult ALL: recommendations from a panel of US experts

ABSTRACT

Measurable residual disease (MRD) is a powerful predictor of clinical outcomes in acute lymphoblastic leukemia (ALL). In addition to its clear prognostic importance, MRD information is increasingly used in clinical decision algorithms to guide therapeutic interventions. Although it is well established that achievement of MRD-negative remission is an important end point of ALL therapy, the prognostic and therapeutic implications of MRD in an individual patient are influenced by both disease-related factors (eg, cytomolecular risk) and assay-related factors (eg, sensitivity, specimen source, and timing of assessment), which add complexity to MRD-guided treatment decisions. In this review, we discuss the data supporting the use of MRD assessment in adult ALL and how this information can rationally inform clinical decisions, including selection of patients for MRD-directed therapies or allogeneic hematopoietic stem cell transplantation. We also discuss important interpretative challenges related to novel high sensitivity next-generation sequencing-based MRD assays, which are becoming increasingly used in clinical practice.

Total body irradiation versus chemotherapy myeloablative conditioning in B-cell acute lymphoblastic leukaemia patients with first complete remission

The best conditioning for hematopoietic stem cell transplantation (HSCT) in acute lymphoblastic leukemia is debated. We analyzed 178 adults undergoing HSCT with total body irradiation (TBI) or chemotherapy conditioning regimens for B-cell leukemia in complete remission 1 (CR1). Both TBI and chemotherapy regimens showed comparable overall survival (OS) and leukemia-free survival (LFS). However, TBI had a trend of reduced relapse (HR 0.56, P = 0.064) but higher non-relapse mortality (NRM, HR 3.23, P = 0.072) due to increased grade 3 to 4 graft-versus-host disease (22.8% vs. 8.8%, P = 0.023). The key factor affecting survival was minimal residual disease (MRD) after three chemotherapy cycles (OS P = 0.004, LFS P = 0.006). In MRD-negative patients, both regimens gave similar LFS and cumulative incidence of relapse (CIR) irrespective of whether the transplantation was allogeneic (allo-HSCT) or autologous (auto-HSCT), but the allo-HSCT group had a lower OS due to higher NRM (5.3% vs. 20.6%, P = 0.020). For MRD-positive patients, TBI was superior in LFS (71.9% vs. 43.9%, P = 0.017) and relapse rate (18.5% vs. 48.7%, P = 0.006). Our research indicates the choice between TBI and non-TBI should be based on MRD after three chemotherapy cycles.

The Changing Role of Allogeneic Stem Cell Transplantation in Adult B-ALL in the Era of CAR T Cell Therapy

The treatment of B-cell acute lymphoblastic leukemia (B-ALL) in adults remains a significant therapeutic challenge. While advances in chemotherapy and targeted and immunotherapies have improved overall survival, relapsed or refractory (r/r) adult ALL is associated with poor outcomes. CD19-directed chimeric antigen receptor (CAR) T-cell therapy has emerged as a transformative option, achieving high remission rates even in heavily pretreated patients. However, relapse is common. Allogeneic hematopoietic stem cell transplantation (allo-HCT), a traditional cornerstone of remission consolidation, may improve long-term outcomes but carries risks of transplant-related mortality (TRM) and morbidity. Most evidence for HCT after CAR T therapy comes from retrospective analyses of subgroups from CAR T cell trials, with small sample sizes and inconsistent data on transplant procedures and outcomes. Despite these limitations, consolidative allo-HCT appears to prolong relapse-free survival (RFS). While overall survival (OS) benefits are in question, extended remission duration has been observed. Nonrelapse mortality (including TRM), ranging from 2.4 to 35%, underscores the need for careful patient selection. Emerging real-world data affirm these findings but highlight the importance of individualized decisions based on disease and treatment history. This review examines current evidence on the sequential use of CD19-directed CAR T-cell therapy and allo-HCT in adults with r/r B-ALL.

Importance of measurable residual disease in the outcome of adults with acute lymphoblastic leukemia after allogeneic stem cell transplantation: Long follow-up analysis from a single transplant center

INTRODUCTION

In this retrospective study, with prolonged follow-up, we analyze the outcomes of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in adult acute lymphoblastic leukemia (ALL) and the impact of pre-transplantation measurable residual disease (pre-HSCT MRD).

METHODS

Detection of MRD was performed by multiparametric flow cytometry (MFC) for Philadelphia chromosome-negative ALL (Ph-neg ALL) and by classic genetic tests for Ph-pos ALL.

RESULTS

Among 46 patients in first complete remission (CR1) who had available MRD data, 1- and 3-year cumulative incidences of relapse (CIR) for patients with positive and negative MRD were 47.1% and 52.9% vs. 3.4% and 6.9%, respectively (p<0.001). Disease free survival (DFS) at 1 and 3 years was 82.8% (95% CI 70.1-97.7) and 79.3% (95% CI 65.9-95.5) in the negative MRD group and 35.3% (95% CI 18.5-67.2) and 29.4% (95% CI 14.1-61.4) in the positive MRD group (p<0.001). With a median follow up of 29 months in the entire cohort and 177.6 months (14.8 years) in survivors, 1- and 3-year overall survival (OS) for the pre-HSCT negative MRD group was 82.8% (95% CI 70.1-97.7) and 79.2% (95% CI 65.6-95.5), respectively, compared to 64.7% (95% CI 45.5-91.9) and 41.2% (95% CI 23.3-72.7) in the positive MRD group (p=0.001). In a multivariate model, positive pre-HSCT MRD is associated with increased CIR and poorer DFS and OS.

CONCLUSION

These results support that pre-HSCT MRD should be eradicated to improve survival of adult ALL patients who undergo allo-HSCT.

Impact of high-sensitivity flow cytometry on peri-transplant minimal residual disease kinetics in acute leukemia

Minimal residual disease (MRD) detected before hematopoietic cell transplantation (HCT) is associated with adverse outcomes in patients with high-risk acute leukemia. However, the ideal time points for post-transplant MRD assessment and the clinical significance of low levels of residual disease in this context are unclear. We conducted a prospective real-world analysis of high-sensitivity flow cytometry MRD performed before and after transplant (at days 30, 60 and 100) in 77 acute leukemia patients. The aim was to evaluate the kinetics of disease elimination and correlate it with transplant outcomes. Pre-transplant MRD was negative in 42 (MRD-) and positive in 35 patients (MRD+). Post-transplant MRD assessment was feasible at day 30 (n = 30, 38.9%), day 60 (n = 27, 35.0%) and day 100 (n = 60, 77.9%). Relapses occurred in 8 patients in the MRD + group (22.9%) and three in the MRD-negative group (7.1%), p = 0.02. Pre-transplant MRD correlated with a decrease in overall survival (OS; 87.9% MRD- vs. 54.0% MRD+) and event-free survival (EFS; 85.3% MRD- vs. 51.1% MRD+), p = 0.001. Cumulative incidence of relapse (CIR) was 17.5% in MRD + vs. 2.6% in MRD- (p = 0.049). Non-relapse mortality (NRM) was 31.4% in MRD + vs. 12.1% in MRD- (p = 0.019). One-year OS was higher in patients with negative MRD at d100 (92.4%, 95% CI: 0.81-0.971) than positive d100 MRD (53.3%, 95% CI: 0.177-0.796), p < 0.0001. Disease status and d100 MRD were associated with OS, EFS and CIR. Differences in NRM between leukemia types (ALL: 18.9% MRD- vs. 50% MRD+, and AML 0% MRD- vs. 21.7% MRD+, p = 0.0158) were also observed. In conclusion, pre-transplant MRD assessed by highly sensitive flow cytometry accurately identified patients with adverse prognoses. Persistent MRD after HCT could predict relapse with high specificity and clinical sensitivity. These results highlight the importance of incorporating peri-transplant MRD kinetics into the routine treatment of acute leukemia, particularly in low/middle-income countries.

Allogeneic Hematopoietic Cell Transplantation With Reduced Toxicity Conditioning for Pediatric B Lymphoid Malignancy

BACKGROUND

Conventional conditioning regimens for children with lymphoid malignancy undergoing allogeneic hematopoietic cell transplantation (HCT) are myeloablative and involve high-dose total body irradiation (TBI). Such regimens are associated with significant late complications.

OBSERVATIONS

Here, we used a reduced-toxicity conditioning regimen comprising fludarabine, cytarabine, melphalan, and low-dose TBI (FLAMEL) to treat 5 patients with lymphoid malignancy before HCT. Four patients maintained complete remission (range, 18 to 63 mo), whereas the remaining patient who had positive minimal residual disease (MRD) before HCT relapsed.

CONCLUSIONS

FLAMEL might be a suitable conditioning regimen for children with lymphoid malignancy if pre-HCT MRD is negative.

Graft Versus Host Disease Prophylaxis in Matched Donor Stem Cell Transplantation: Post-transplantation Cyclophosphamide Combinations Versus Methotrexate/Tacrolimus

BACKGROUND

The use of post-transplant cyclophosphamide (PTCy) is highly effective in preventing graft versus host disease (GVHD) for haploidentical allogeneic hematopoietic stem cell transplantation (allo-HSCT). There is limited data on the role of PTCy as GVHD prophylaxis in matched-sibling and fully matched-unrelated donor (MSD/MUD) allo-HSCT.

METHODS

Our single-center retrospective study aims to compare outcomes of PTCy alone or in combination with mycophenolate mofetil and tacrolimus (PTCy/MMF/TAC) relative to methotrexate and tacrolimus (MTX/TAC). The primary endpoint of our study was GVHD-free, relapse free survival (GRFS). Secondary endpoints were overall survival (OS), disease free survival (DFS), and incidence of severe acute and chronic GVHD. We identified 74 adult patients who underwent MSD/MUD allo-HSCT at our institution from 2015 to 2023.

RESULTS

Within our cohort, 33.8% (n = 25) received MTX/TAC, while 54.0% (n = 40) received PTCy/MMF/TAC, and 12.2% (n = 9) received PTCy alone. Patients receiving PTCY had the longest time to neutrophil engraftment relative to MTX/TAC (15 days vs. 12 days, P = .010). PTCy/MMF/TAC was associated with improved GRFS relative to MTX/TAC (hazard ratio [HR] = HR 0.42, 95% CI 0.19-0.93, P = .031), which persisted when controlling for age. Incidence of chronic GVHD was lower in the PTCy/MMF/TAC group compared to MTX/TAC (1-year 9.0% vs. 30.1%, HR 0.19, 95% CI 0.06-0.59, P = .005). However, OS and DFS were comparable across all groups.

CONCLUSIONS

Our results demonstrate decreased rates of severe chronic GVHD resulting in improved GRFS when using PTCy/TAC/MTX as GVHD prophylaxis compared to MTX/TAC in MSD/MUD.

Total body irradiation versus thiotepa/busulfan-based conditioning regimens for myeloablative allogeneic stem cell transplantation in adults with acute lymphoblastic leukemia

Total body irradiation (TBI)-based conditioning regimens are generally recommended for allogeneic HSCT (allo-HSCT) in patients with acute lymphoblastic leukemia (ALL). Recent evidence suggests that modern chemotherapy-based regimens may be as effective. This multicenter retrospective study compared the clinical outcomes of myeloablative allo-HSCT with thiotepa, busulfan, and cyclophosphamide/fludarabine (TTB) to TBI-based conditioning. Between 2002 to 2018, 63 and 114 patients received TTB- and TBI-based conditioning regimens, respectively. The 5-year cumulative incidence of relapse was lower in the TBI cohort compared to the TTB cohort (30% [95% CI, 22-38] versus 47% [95% CI, 36-59]; P = 0.03). Multivariate analysis identified T-ALL, Ph-negative B-ALL, and measurable residual disease associated with a higher relapse risk. The 5-year cumulative incidence of non-relapsed mortality (NRM) was significantly lower with TTB (12% [95% CI, 5-20]) compared to TBI (25% [95% CI, 18-33]) (P = 0.001). Multivariate analysis found TBI conditioning, older age, and advanced stages of ALL at transplantation associated with a higher NRM. No statistical difference was seen in overall survival (49% [95% CI, 40-58] and 46% [95% CI, 35-60]) in the TBI and TTB groups, respectively; P = 0.9). The study suggests that TTB-based conditioning may be a promising option for ALL patients undergoing allo-HSCT, as it resulted in similar OS and lower NRM than TBI-based conditioning.

Management of ALL in adults: 2024 ELN recommendations from a European expert panel

ABSTRACT

Experts from the European Leukemia Net (ELN) working group for adult acute lymphoblastic leukemia have identified an unmet need for guidance regarding management of adult acute lymphoblastic leukemia (ALL) from diagnosis to aftercare. The group has previously summarized their recommendations regarding diagnostic approaches, prognostic factors, and assessment of ALL. The current recommendation summarizes clinical management. It covers treatment approaches, including the use of new immunotherapies, application of minimal residual disease for treatment decisions, management of specific subgroups, and challenging treatment situations as well as late effects and supportive care. The recommendation provides guidance for physicians caring for adult patients with ALL which has to be complemented by regional expertise preferably provided by national academic study groups.

Minimal Residual Disease in the Management of B-Cell Acute Lymphoblastic Leukemia: A Systematic Review of Studies from Indian Settings

Minimal residual disease (MRD) has become an essential tool in the management of B-cell acute lymphoblastic leukemia (B-ALL) and aids in tailoring treatment strategies to suit specific patient needs. Although much progress has been made in this area, there is limited data on the use of MRD in the Indian context. Our objective was to identify relevant literature that discusses the utility of MRD in the management of B-cell ALL in adolescents and young adults (AYA) and adults in Indian settings. A systematic search and screening of articles were performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The primary data source was PubMed followed by Google Scholar for articles and conference proceedings. Of the 254 records screened, 24 records were retained for analysis. MRD monitoring had a significant role in the management of AYA/adult B-cell ALL patients. Variability of results was observed across these studies with respect to methods, techniques, and use. However, these studies evidenced and validated the importance of MRD assessment in risk-adapted management of B-cell ALL and highlighted the need for optimization. The advances in MRD diagnostics and applications are yet to be tested and adopted in Indian settings. Hence, there is a need for in-depth research to develop and optimize approaches for calibrating country-specific management strategies. The potential role of MRD assessments in anticipating relapse or treatment failures warrants more attention for the preemptive positioning of novel strategies involving immunotherapies.

Survival outcomes in patients with relapsed/refractory or MRD-positive B-cell acute lymphoblastic leukemia treated with blinatumomab

Blinatumomab has demonstrated significant efficacy in adult and pediatric patients with relapsed/refractory B-cell acute lymphoblastic leukemia (R/R B-cell ALL) and patients with measurable residual disease (MRD). This review aimed to compare median relapse-free survival (RFS) and median overall survival (OS) in adult and pediatric patients with R/R or MRD-positive B-cell ALL from pivotal studies [MT-103-211 and TOWER for adults with Philadelphia chromosome (Ph)-negative R/R B-cell ALL, ALCANTARA for adults with Ph-positive R/R B-cell ALL, MT-103-203 for adults with MRD-positive B-cell ALL, and MT-103-205 for pediatric patients with R/R B-cell ALL], with the median RFS and OS from retrospective analyses, country or ethnicity-specific studies, and studies based on real-world evidence (RWE) identified from a literature search. Adults with Ph-negative R/R B-cell ALL who received blinatumomab as first salvage demonstrated a numerically longer median OS compared with that in patients from pivotal studies (MT-103-211 and TOWER) without additional safety concerns. In pediatric patients with R/R B-cell ALL treated with blinatumomab, the median RFS and OS from retrospective analyses and country/ethnicity-specific studies were comparable with the median RFS and OS from the pivotal study MT-103-205. The median RFS and OS from RWE studies in adults with R/R B-cell ALL were numerically longer than the median RFS and OS from pivotal studies (MT-103-211, TOWER, and ALCANTARA); however, this trend was not observed in pediatric patients with R/R B-cell ALL. In conclusion, this analysis identified first salvage adults with Ph-negative R/R B-cell ALL as particularly well-suited for treatment with blinatumomab since survival outcomes from retrospective analyses reported in this patient subgroup were numerically better compared with those from pivotal studies without additional safety signals.

The current landscape: Allogeneic hematopoietic stem cell transplant for acute lymphoblastic leukemia

One of the consistent features in development of hematopoietic stem cell transplant (HCT) for Acute Lymphoblastic Leukemia (ALL) is the rapidity with which discoveries in the laboratory are translated into innovations in clinical care. Just a few years after murine studies demonstrated that rescue from radiation induced marrow failure is mediated by cellular not humoral factors, E. Donnall Thomas reported on the transfer of bone marrow cells into irradiated leukemia patients. This was followed quickly by the first descriptions of Graft versus Leukemia (GvL) effect and Graft versus Host Disease (GvHD). Despite the pivotal nature of these findings, early human transplants were uniformly unsuccessful and identified the challenges that continue to thwart transplanters today - leukemic relapse, regimen related toxicity, and GvHD. While originally only an option for young, fit patients with a matched family donor, expansion of the donor pool to include unrelated donors, umbilical cord blood units, and more recently the growing use of haploidentical donors have all made transplant a more accessible therapy for patients with ALL. Novel agents for conditioning, prevention and treatment of GvHD have improved outcomes and investigators continue to develop novel treatment strategies that balance regimen related toxicity with disease control. Our evolving understanding of how to prevent and treat GvHD and how to prevent relapse are incorporated into novel clinical trials that are expected to further improve outcomes. Here we review current considerations and future directions for both adult and pediatric patients undergoing HCT for ALL, including indication for transplant, donor selection, cytoreductive regimens, and outcomes.

Association of CDKN2A/B mutations, PD-1, and PD-L1 with the risk of acute lymphoblastic leukemia in children

PURPOSE

Currently, the significance of CDKN2A/B mutations in the pathogenesis and prognosis of acute lymphoblastic leukemia (ALL) is inconclusive. In this study, we analyzed the genetic and clinical features of children with CDKN2A/B mutations in ALL. In addition, we evaluated the expression and significance of programmed cell death protein 1 (PD-1) and programmed cell death ligand 1 (PD-L1) in serum and explored their role in the susceptibility of childhood ALL.

METHODS

We sequenced CDKN2A/B in the peripheral blood of 120 children with ALL and 100 healthy children with physical examination. The levels of CD4+ T, CD8+ T, and NK cells were measured by flow cytometry (FCM). Furthermore, the expression of PD-1 and PD-L1 was detected by ELISA.

RESULTS

We found 32 cases of CDKN2A rs3088440 and 11 of CDKN2B rs2069426 in 120 ALL children. Children with ALL in the CDKN2A rs3088440 were more likely to have hepatosplenomegaly (P = 0.019) and high risk (P = 0.014) than the wild group. In contrast, CDKN2B rs2069426 was more likely to develop lymph node metastasis (P = 0.017). The level of PD-L1 in the serum of ALL children was significantly higher than that of the control group, and there was no significant difference in PD-1 (P < 0.001). Additionally, children with CDKN2A rs3088440 had reduced CD8+ T cell counts than the wild group (P = 0.039).

CONCLUSION

CDKN2A rs3088440 and CDKN2B rs2069426 may be related to the occurrence and development of ALL in Chinese children. Additionally, PD-1/PD-L1 may be involved in the immune escape process of ALL, which is expected to become a new target for the treatment of the disease.

The results of the modified St Jude Total Therapy XV Protocol in the treatment of low- and middle-income children with acute lymphoblastic leukemia

The St Jude Total Therapy Study XV was the first clinical trial to prospectively use minimal residual disease levels during and after remission induction therapy to guide risk-directed treatment. We used the Total Therapy XV protocol with minimal modification in treating 115 newly diagnosed pediatric acute lymphoblastic leukemia patients from low- and middle-income groups from January 2011 to December 2017. The mean age at diagnosis was 5.97 ± 3.96 years. The median follow-up period was 88 months. Three (2.6%) patients had bone marrow relapse, and one (0.87%) had an isolated central nervous system relapse. Nineteen of the patients (16.52%) died due to infection-related complications, three (2.61%) died due to progressive disease, and one (0.87%) died due to hematopoietic stem cell transplant complications. Five-year overall survival was 80%, and event-free survival was 78.3%. Our results showed that the Total XV treatment protocol could be used successfully in patients with ALL from low- and middle-income populations. However, infection-related deaths remain a significant problem.

Effects of isolated central nervous system involvement evaluated by multiparameter flow cytometry prior to allografting on outcomes of patients with acute lymphoblastic leukemia

Introduction

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a major strategy to cure patients with acute lymphoblastic leukemia (ALL). The aim of this study was to evaluate whether isolated flow cytometry (FCM)-positive central nervous system (CNS) involvement before allo-HSCT is clinically significant.

Methods

The effects of isolated FCM-positive CNS involvement prior to transplantation on the outcomes of 1406 ALL patients with complete remission (CR) were retrospectively investigated.

Results

Patients were classified into isolated FCM-positive CNS involvement (n=31), cytology-positive CNS involvement (n = 43), and negative CNS involvement (n = 1332) groups. Among the three groups, the 5-year cumulative incidence of relapse (CIR) values were 42.3%, 48.8%, and 23.4%, respectively (P<0.001). The 5-year leukemia-free survival (LFS) values were 44.7%, 34.9%, and 60.8%, respectively (P<0.001). Compared with the negative CNS group (n=1332), the 5-year CIR of the pre-HSCT CNS involvement group (n=74) was higher (46.3% vs. 23.4%, P<0.001], and the 5-year LFS was inferior (39.1% vs. 60.8%, P<0.001). Multivariate analysis indicated that four variables, T-cell ALL, in second complete remission or beyond (CR2+) at HSCT, pre-HSCT measurable residual disease positivity, and pre-HSCT CNS involvement, were independently associated with a higher CIR and inferior LFS. A new scoring system was developed using the following four variables: low-risk, intermediate-risk, high-risk, and extremely high-risk groups. The 5-year CIR values were 16.9%, 27.8%, 50.9%, and 66.7%, respectively (P<0.001), while the 5-year LFS values were 67.6%, 56.9%, 31.0%, and 13.3%, respectively (P<0.001).

Conclusion

Our results suggest that ALL patients with isolated FCM-positive CNS involvement are at a higher risk of recurrence after transplantation. Patients with pre-HSCT CNS involvement had higher CIR and inferior survival outcomes.

Immunophenotypic measurable residual disease monitoring in adult acute lymphoblastic leukemia patients undergoing allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) offers a survival benefit to adult patients affected by acute lymphoblastic leukemia (ALL). However, to avoid an overt disease relapse, patients with pre or post transplant persistence or occurrence of measurable residual disease (MRD) may require cellular or pharmacological interventions with eventual side effects. While the significance of multiparametric flow cytometry (MFC) in the guidance of ALL treatment in both adult and pediatric patients is undebated, fewer data are available regarding the impact of MRD monitoring, as assessed by MFC analysis, in the allo-HSCT settings. Aim of this article is to summarize and discuss currently available information on the role of MFC detection of MRD in adult ALL patients undergoing allo-HSCT. The significance of MFC-based MRD according to sensitivity level, timing, and in relation to molecular techniques of MRD and chimerism assessment will be also discussed.

Immunotherapy and Allogeneic Bone Marrow Transplantation in B Acute Lymphoblastic Leukemia: How to Sequence?

Long-term disease control is achieved in 80-90% of patients with acute lymphoblastic leukemia of B origin (B-ALL). About half of adult and 10% of pediatric patients develop refractory or relapsed disease, whereas survival after relapse accounts about 10% in adults and 30-50% in children. Allogeneic bone marrow transplantation offers remarkable benefit in cases with unfavorable outcome. Nevertheless, novel immunotherapeutic options have been approved for patients with adverse prognosis. Immunotherapeutic agents, nowadays, are preferred over standard chemotherapy for patients with relapsed or refractory B-ALL The mode of action, efficacy and safety data of immunotherapeutic agents released, indications and sequence of those therapies over the course of treatment, are herein reviewed.

MRD in ALL: Optimization and Innovations

PURPOSE OF REVIEW

Measurable residual disease (MRD) is an important monitoring parameter that can help predict survival outcomes in acute lymphoblastic leukemia (ALL). Identifying patients with MRD has the potential to decrease the risk of relapse with the initiation of early salvage therapy and to help guide decision making regarding allogeneic hematopoietic cell transplantation. In this review, we discuss MRD in ALL, focusing on advantages and limitations between MRD testing techniques and how to monitor MRD in specific patient populations.

RECENT FINDINGS

MRD has traditionally been measured through bone marrow samples, but more data for evaluation of MRD via peripheral blood is emerging. Current and developmental testing strategies for MRD include multiparametric flow cytometry (MFC), next-generation sequencing (NGS), quantitative polymerase chain reaction (qPCR), and ClonoSeq. Novel therapies are incorporating MRD as an outcome measure to demonstrate efficacy, including blinatumomab, inotuzumab ozogamicin, and chimeric antigen receptor T (CAR-T) cell therapy. Understanding how to incorporate MRD testing into the management of ALL could improve patient outcomes and predict efficacy of new therapy options.

Prognostic implication of early minimal residual disease evaluation in patients with chronic myelomonocytic leukemia

To investigate the prognostic implication of minimal residual disease (MRD) evaluation in chronic myelomonocytic leukemia (CMML), we conducted a restropective study included a total of 174 CMML patients in our hospital from January 2010 to March 2021. In which 50/174 (29%) bone marrow samples were conducted by multiparameter flow cytometry (FCM) assessed MRD analysis after the first three cycles of treatment and were included in this study. MRD was detected by six- to eight-colour FCM. The achievement of early MRD negativity had better clinical outcomes in patients with CMML, which fared better prognosis in terms of not only PFS (P=0.006) but also OS (P=0.02) after the first cycle, and PFS (P=0.023 and P=0.041) after the second and third cycles, whereas no significantly influence in OS. In addition, MRD negative after initial treatment remained its independent prognostic value associated with PFS (adjusted hazard ratio [HR] 0.161, 95 CI 0.035-0.738; P=0.019) and OS (adjusted HR 0.136; 95 CI 0.017-1.077; P=0.059), indicating that patients with MRD-negative after the initial treatment alone could obtain the greatest clinical benefit. According to MRD level, the patients were divided into 4 different groups: very low risk (fewer than 10^-4 cells) in 15 cases, low risk (10^-4 to 10^-3 cells) in 6; and 6 were at intermediate risk (fewer than 10^-3 to 10^-2 cells). The rest of 23 patients were were assigned to the high-risk grades (more than 10^-2 residual cells), we find this risk stratification model is significantly associated with better PFS (P=0.002) but marginal significantly associated with OS (P=0.068). Notably, patients with DNMT3A mutation fared a shorter PFS in the MRD positive subgroup (P=0.068). MRD is highly predictive of prognosis, and its combination with molecular profile may help identify patients at increased risk for progression to further improve the management of patients with CMML. Large-scaled investigations are warranted to validate our conclusions and its potential in clinical practice.

Controversies in the Treatment of Adolescents and Young Adults with Philadelphia Chromosome-Negative B-Cell Acute Lymphoblastic Leukemia

PURPOSE OF THE REVIEW

The incidence of acute lymphoblastic leukemia (ALL) has been increasing steadily in the adolescent and young adult (AYA) population. In this review article focused on the management of AYAs with Philadelphia chromosome-negative (Ph-) B-ALL, we examine topics of clinical interest and identify areas of controversy in need of further investigation.

RECENT FINDINGS

We explore four areas of active investigation: pediatric-inspired front-line treatment regimens, the optimal time of measurable residual disease (MRD) assessment, the role of hematopoietic stem cell transplant and the optimal salvage therapy for relapsed/refractory B-ALL in AYAs. There has been rapid advancement in the management of ALL in the AYA patient population, which has resulted in improved outcomes. We must build on the successes by continuing to promote multi-center innovative clinical research with clinical trial populations reflecting the AYA ALL patient spectrum. The incorporation of novel targeted immunotherapy into front-line treatment will be transformative and redefine treatment paradigms in the coming years.

Prognostics and Clinical Outcomes in Patients Diagnosed With Acute Lymphoblastic Leukemia in King Abdulaziz University Hospital, Jeddah, Saudi Arabia

Background

Acute lymphoblastic leukemia (ALL) is a hematological cancer that causes an accumulation of immature cells in the bone marrow. The count of white blood cells (WBCs) is an independent predictor of survival. Integrating first-line treatment, such as intensive chemotherapy, with prognostic factors aids in developing critical therapeutic decisions and improving long-term outcomes. This study evaluated several prognostics such as age, WBCs, ALL cell subtypes, and absolute WBC counts.

Methods

This study involved a retrospective record review and was conducted by scanning the medical records of all individuals who developed ALL and were on chemotherapy at a teaching Hospital in Jeddah between 2012 and 2018. The data entry was done using Microsoft Excel, while the analysis was done using SPSS Version 21. To test any associations, frequency and measure of central tendencies, t-test, and chi-square test were used.

Results

A total of 98 of ALL patients were on chemotherapy, and 18 were excluded. Thus, 80 patients were analyzed. The mean age for all patients was 13.6 years (range: 0.6-26.6 years), and the most frequent ages were less than 18 years (90%). More than half of them (62.5%) were males. The majority of the patients were Bangladeshi, Pakistani, Indian, Afghan, Indonesian, and Myanmar (37.7%), and the least were Saudi (3.8%). B subtype (75.9%) was more common than T subtype (24.1%). The first remission after treatment was in 66 patients, with a mean of 6.86 years. There was a significant adverse relationship between the ability of patients to reach the first remission and WBC count (p = 0.032). There was strong significant negative correlation between absolute lymphocyte count (ALC) and survival duration after treatment (r = -0.669; p = 0.012).

Conclusions

The impact regarding age and WBC is almost like most previous studies. ALC shows a strong poor prognosis, while ALL cell subtypes demonstrate a contradictory prognosis effect.

How I Use Measurable Residual Disease in the Clinical Management of Adult Acute Lymphoblastic Leukemia

Over the last decade the use of measurable residual disease (MRD) diagnostics in adult acute lymphoblastic leukemia (ALL) has expanded from a limited number of study groups in Europe and the United States to a world-wide application. In this review, we summarize the advantages and drawbacks of the current available techniques used for MRD monitoring. Through the use of three representative case studies, we highlight the advances in the use of MRD in clinical decision-making in the management of ALL in adults. We acknowledge discrepancies in MRD monitoring and treatment between different countries, reflecting differing availability, accessibility and affordability.

Improved survival in adolescents and young adults (AYA) patients aged 14-55 years with acute lymphoblastic leukemia using pediatric-inspired protocol - a retrospective analysis of a real-world experience in 79 of patients treated at a national tertiary care referral center

Background

Treating adolescents and young adults (AYA) patients with acute lymphoblastic leukemia (ALL) using pediatric-inspired protocols have shown improvement in outcomes. Most data available in the literature of such protocols is derived from well-controlled clinical trials. This report aims to provide a real-world experience from using a pediatric-inspired protocol in ALL-AYA population in larger number of patients treated at a national tertiary care referral center.

Methods

Newly diagnosed Philadelphia negative ALL-AYA patients ages between 14 and 55 years of age were treated on an institutional protocol (AYA-15 protocol) adopted from a modified version of Children's Cancer Group (CCG) 1900 protocol. At the time of this publication, a total of 79 patients were treated using the AYA-15 protocol between 2015 and 2020). Event-free survival (FFS), disease-free survival (DFS), and overall survival (OS) were analyzed using cumulative incidence and Kaplan-Meier methods.

Results

The median age at diagnosis was 18 years (14–51 years) with 63% male patients. Complete remission (CR) at day 28 of induction was achieved in 88.6% of which 73.4% were minimal residual disease (MRD) negative. At a median follow up of 5 years, EFS, DFS and OS were 57.5%, 69.2% and 75.8% respectively. Toxicities were within the expected range with infections and transaminitis being the most common adverse events.

Conclusion

Our single-center experience real-world data in treating AYA-ALL patients with pediatric-inspired protocol demonstrates encouraging results of high survival rate and excellent tolerability for patients aged 18–55 years.

Clinical experience of CAR T cells for B cell acute lymphoblastic leukemia

Chimeric antigen receptor (CAR) T cell therapy has transformed the treatment for both pediatric and adult patients with relapsed or refractory (R/R) B cell acute lymphoblastic leukemia (B-ALL). Clinical trial results across multiple institutions with different CAR constructs report significant response rates in treated patients. One product (tisagenlecleucel) is currently FDA approved for the treatment of R/R B-ALL in patients <26 y/o. Successful application of this therapy is limited by high relapse rates, potential for significant toxicity, and logistical issues surrounding collection/production. Herein, we review published data on the use of CAR T cells for B-ALL, including results from early pivotal clinical trials, relapse data, incidence of toxicity, and mechanisms to optimize CAR T cell therapy.

Disruption of the oral microbiota is associated with a higher risk of relapse after allogeneic hematopoietic stem cell transplantation

Intestinal microbiota (IM) diversity and composition regulates host immunity and affects outcomes after allogeneic stem cell transplantation (allo-HSCT). We evaluated if the oral mucosa microbiota (OM) could impact the outcomes in patients who underwent allo-HSCT. Samples from the oral mucosa of 30 patients were collected at three time points: before the conditioning regimen, at aplasia, and at engraftment. We analyzed the associations of OM diversity and composition with allo-HSCT outcomes. Lower OM diversity at preconditioning was associated with a higher risk of relapse at 3 years (68% versus 33%, respectively; P = 0.04). Dominance (relative abundance ≥ 30%) by a single genus at preconditioning was also associated with a higher risk of relapse (63% versus 36% at 3 years, respectively; P = 0.04), as well as worse progression-free survival (PFS; 19% versus 55%, respectively; P = 0.01), and overall survival (OS) at 3 years (38% versus 81%, respectively; P = 0.02). In our study we observed that OM dysbiosis is associated with a higher risk of relapse and worse survival after allo-HSCT.

Association of minimal residual disease with clinical outcomes in Philadelphia chromosome positive acute lymphoblastic leukemia in the tyrosine kinase inhibitor era: A systemic literature review and meta-analysis

Minimal residual disease (MRD) appeared to be a potent prognostic indicator in patients with Philadelphia chromosome positive acute lymphoblastic leukemia (Ph+ ALL), with potential value in informing individualized treatment decisions. Hence, we performed herein a systemic literature review and meta-analysis to comprehensively address the prognostic value of MRD in Ph+ ALL. Systematic literature review was conducted in PubMed, Embase, and Cochrane databases with the data access date up to September 23, 2020. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated with fixed-effects or random-effects models. Furthermore, subgroup analyses were performed to assess the robustness of the associations. 27 studies with a total number of 3289 patients were eligible for this meta-analysis. Combined HRs suggested that MRD positivity was associated with inferior event-free survival (EFS) (HR = 2.00, 95% CI 1.77–2.26) and overall survival (OS) (HR = 2.34, 95% CI 1.86–2.95). The associations remained statistically significant in subgroup analyses including age group, MRD timing, disease status at MRD, MRD cutoff level, et al. Our findings suggested MRD as a potent clinical tool for assessing the prognosis of Ph+ ALL. Further studies using MRD-based risk stratification might help optimize individualized treatment strategies for Ph+ ALL patients.

The evolving role of allogeneic haematopoietic cell transplantation in the era of chimaeric antigen receptor T-cell therapy

Chimaeric antigen receptor T-cell (CAR T) therapy has revolutionized the management of many haematological malignancies. It is associated with impressive disease responses in relapsed or refractory high-grade B-cell non-Hodgkin lymphoma (B-NHL) and acute lymphoblastic leukaemia (B-ALL) with durable remissions in a subset of patients. Historically, haematopoietic cell transplantation (HCT) has been the standard consolidation strategy for many of these patients who are now being treated with CAR T. Relapses are frequent after CD19 CAR T therapy in B-ALL and consolidation with allogeneic HCT (allo-HCT) may improve survival of patients with high-risk disease. There appears to be a clear difference in B-ALL outcomes between paediatric and adult patients, with the latter having a much higher risk of relapse after CAR T therapy. Late relapses are infrequent in patients with B-NHL and consolidation with allo-HCT may not be needed in patients who achieve a complete remission after CAR T therapy. Future registry-based and prospective studies will hopefully provide the needed data in the future to risk-stratify the recipients of CAR T therapy. Meanwhile, we provide guidance on patient selection and practical issues with performing allo-HCT after CAR T therapy.

MRD-Based Therapeutic Decisions in Genetically Defined Subsets of Adolescents and Young Adult Philadelphia-Negative ALL

Simple Summary

In acute lymphoblastic leukemia (ALL), once a complete remission is achieved following induction chemotherapy, the study of submicroscopic minimal residual disease (MRD) represents a highly sensitive tool to assess the efficacy of early chemotherapy courses and predict outcome. Because of the significant therapeutic progress occurred in adolescent and young adult (AYA) ALL, the importance of MRD in this peculiar age setting has grown considerably, to refine individual prognostic scores within different genetic subsets and support specific risk and MRD-oriented programs. The evidence coming from the most recent MRD-based studies and the new therapeutic directions for AYA ALL are critically reviewed according to ALL subset and risk category.

Abstract

In many clinical studies published over the past 20 years, adolescents and young adults (AYA) with Philadelphia chromosome negative acute lymphoblastic leukemia (Ph− ALL) were considered as a rather homogeneous clinico-prognostic group of patients suitable to receive intensive pediatric-like regimens with an improved outcome compared with the use of traditional adult ALL protocols. The AYA group was defined in most studies by an age range of 18–40 years, with some exceptions (up to 45 years). The experience collected in pediatric ALL with the study of post-induction minimal residual disease (MRD) was rapidly duplicated in AYA ALL, making MRD a widely accepted key factor for risk stratification and risk-oriented therapy with or without allogeneic stem cell transplantation and experimental new drugs for patients with MRD detectable after highly intensive chemotherapy. This combined strategy has resulted in long-term survival rates of AYA patients of 60–80%. The present review examines the evidence for MRD-guided therapies in AYA’s Ph− ALL, provides a critical appraisal of current treatment pitfalls and illustrates the ways of achieving further therapeutic improvement according to the massive knowledge recently generated in the field of ALL biology and MRD/risk/subset-specific therapy

[Comparison of prognostic significance between multiparameter flow cytometry and real-time quantitative polymerase chain reaction in the detection of minimal residual disease of Philadelphia chromosome-positive acute B lymphocytic leukemia before allogeneic hematopoietic stem cell transplantation]

目的

探讨多参数流式细胞术（MFC）与实时定量聚合酶链反应技术（RQ-PCR）两种方法检测费城染色体阳性（Ph⁺）急性B淋巴细胞白血病（B-ALL）患者异基因造血干细胞移植（allo-HSCT）前微小残留病（MRD）的预后意义。

方法

回顾性分析2014年7月至2018年2月在北京大学血液病研究所接受allo-HSCT的280例Ph⁺ B-ALL患者，同时用MFC和RQ-PCR法（检测BCR-ABL融合基因表达）检测移植前MRD。

结果

RQ-PCR与MFC检测MRD具有相关性（rs＝0.435，P<0.001）。MFC、RQ-PCR法检测移植前MRD的阳性率分别为25.7％（72/280）、60.7％（170/280）。移植前MFC-MRD阳性组患者移植后白血病3年累积复发率（CIR）明显高于MFC-MRD阴性组（23.6％对8.6％，P<0.001）。RQ-PCR检测BCR/ABL融合基因阳性组（RQ-PCR MRD阳性组）的3年CIR、非复发死亡（NRM）、无白血病生存（LFS）、总生存（OS）与BCR/ABL融合基因阴性组（RQ-PCR MRD阴性组）相比差异均无统计学意义（P>0.05）。移植前RQ-PCR MRD≥1％组比<1％组具有更高的3年CIR（23.1％对11.4％，P＝0.032）、更低的LFS率（53.8％对74.4％，P＝0.015）与OS率（57.7％对79.1％，P＝0.009）。多因素分析显示，移植前MFC-MRD阳性是影响移植后CIR的危险因素（HR＝2.488，95％CI1.216～5.088，P＝0.013），移植前RQ-PCR MRD≥1％是影响LFS（HR＝2.272，95％CI 1.225～4.215，P<0.001）、OS（HR＝2.472，95％ CI 1.289～4.739，P＝0.006）的危险因素。MFC检测MRD预测复发的敏感性、特异性、阳性预测值（PPV）、阴性预测值（NPV）分别为48.50％、77.56％、23.62％、87.16％。以RQ-PCR MRD≥1％预测复发的敏感性、特异性、PPV、NPV分别为23.00％、88.59％、17.15％、91.84％。移植前MFC-MRD阳性或RQ-PCR MRD≥1％二者任一成立为指标预测移植后复发的敏感性、特异性、PPV、NPV分别为54.29％、73.88％、45.70％、91.87％。

结论

MFC和RQ-PCR法检测移植前MRD水平均可预测Ph⁺ B-ALL患者移植预后。移植前MFC-MRD阳性是移植后复发的危险因素。联合使用两种方法（移植前MFC-MRD阳性状态或RQ-PCR MRD≥1％成立）可提高预测移植后复发的敏感性、阳性预测值与阴性预测值，有助于更好筛选出高危患者。

Improved survival in adolescents and young adults (AYA) patients aged 14-55 years with acute lymphoblastic leukemia using pediatric-inspired protocol - a retrospective analysis of a real-world experience in 79 of patients treated at a national tertiary care referral center

BACKGROUND

Treating adolescents and young adults (AYA) patients with acute lymphoblastic leukemia (ALL) using pediatric-inspired protocols have shown improvement in outcomes. Most data available in the literature of such protocols is derived from well-controlled clinical trials. This report aims to provide a real-world experience from using a pediatric-inspired protocol in ALL-AYA population in larger number of patients treated at a national tertiary care referral center.

METHODS

Newly diagnosed Philadelphia negative ALL-AYA patients ages between 14 and 55 years of age were treated on an institutional protocol (AYA-15 protocol) adopted from a modified version of Children's Cancer Group (CCG) 1900 protocol. At the time of this publication, a total of 79 patients were treated using the AYA-15 protocol between 2015 and 2020). Event-free survival (FFS), disease-free survival (DFS), and overall survival (OS) were analyzed using cumulative incidence and Kaplan-Meier methods.

RESULTS

The median age at diagnosis was 18 years (14-51 years) with 63% male patients. Complete remission (CR) at day 28 of induction was achieved in 88.6% of which 73.4% were minimal residual disease (MRD) negative. At a median follow up of 5 years, EFS, DFS and OS were 57.5%, 69.2% and 75.8% respectively. Toxicities were within the expected range with infections and transaminitis being the most common adverse events.

CONCLUSION

Our single-center experience real-world data in treating AYA-ALL patients with pediatric-inspired protocol demonstrates encouraging results of high survival rate and excellent tolerability for patients aged 18-55 years.

Value of pre-transplant consolidation chemotherapy in adults with acute lymphoblastic leukemia undergoing allogeneic hematopoietic stem cell transplantation without minimal residual disease in first complete remission

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is recommended for adults acute lymphoblastic leukemia (ALL) with minimal residual disease (MRD) negative during their first complete remission (CR1). However, the role of pre-transplant consolidation chemotherapy remains unclear. We evaluated 78 CR1/MRD-negative patients, the consolidation and non-consolidation groups had similar 5-year OS (74.8% [95% CI: 62.2-87.3%] vs. 74.2% [95% CI: 53.2-95.1%], p = .894), RFS (72.2% [95% CI: 59.6-84.7%] vs. 73.1% [95% CI: 54.2-91.9%], p = .942), CIR (9.4% [95% CI: 9.1-9.7%] vs. 18.9% [95% CI: 17.3-20.4%], p = .376), and NRM (18.4% [95% CI: 17.7-19.0%] vs. 8.0% [95% CI: 7.3-8.6%], p = .375). Multivariable analysis confirmed that high cytogenetic risk independently predicted poor OS and RFS, although pre-transplant consolidation chemotherapy did not predict the prognosis. Based on these findings, we recommend performing transplantation immediately for adult ALL patients after they have achieved CR1/MRD-negative status when there are readily available donors.

Low toxicity and favorable overall survival in relapsed/refractory B-ALL following CAR T cells and CD34-selected T-cell depleted allogeneic hematopoietic cell transplant

To define the tolerability and outcome of allogeneic hematopoietic stem cell transplant (allo-HSCT) following CAR T-cell therapy, we retrospectively reviewed pediatric/young adult patients with relapsed/refractory B-ALL who underwent this treatment. Fifteen patients (median age 13 years; range 1-20 years) with a median potential follow-up of 39 months demonstrated 24-month cumulative incidence of relapse, cumulative incidence of TRM, and OS of 16% (95% CI: 0-37%), 20% (95% CI: 0-40%), and 80% (95% CI: 60-100%), respectively. Severe toxicity following CAR T cells did not impact OS (p = 0.27), while greater time from CAR T cells to allo-HSCT (>80 days) was associated with a decrease in OS. In comparing CD34-selected T-cell depleted (TCD; n = 9) vs unmodified (n = 6) allo-HSCT, the cumulative incidence of relapse, TRM, and OS at 24 months was 22% (95% CI: 0-49%) vs 0% (p = 0.14), 0% vs 50% [95% CI: 10-90%] (p = 0.02) and 100% vs 50% [95% CI: 10-90%] (p = 0.02). In this small cohort of patients, CAR T cells followed by a CD34-selected TCD allo-HSCT appears to result in less TRM and favorable OS when compared with unmodified allo-HSCT. There was no evidence that disease control was impacted by the type of consolidative allo-HSCT, which demonstrates the feasibility of this approach.

Dynamic prediction of relapse in patients with acute leukemias after allogeneic transplantation: Joint model for minimal residual disease

INTRODUCTION

Relapse remains the leading cause of treatment failure after allogeneic hematopoietic stem cell transplantation (alloHSCT) in leukemia. Numerous investigations have demonstrated that minimal residual disease (MRD) before or after alloHSCT is prognostic of relapse risk. These MRD data were collected at specific checkpoints and could not dynamically predict the relapse risk after alloHSCT, which needs serial monitoring.

METHODS

In the present study, we retrospectively analyzed MRD measured with multi-parameter flow cytometry in 207 acute myeloid leukemia (AML) patients (acute promyelocytic leukemia excluded), and 124 acute B lymphoblastic leukemia (ALL) patients. A three-step method based on joint model was used to build a relapse risk prediction model.

RESULTS

The 3-year overall survival and relapse-free survival rates of the entire cohort were 67.1% ± 2.8% and 61.6% ± 2.8%, respectively. The model included disease status before alloHSCT, acute and chronic graft-versus-host disease, and serial MRD data. The time-dependent receiver operating characteristics was used to evaluate the ability of the model. It fitted well with actual incidence of relapse. The serial MRD data collected after alloHSCT had better discrimination capabilities for recurrence prediction with the area under the curve from 0.67 to 0.91 (AML: 0.66-0.89; ALL: 0.70-0.96).

CONCLUSION

The joint model was able to dynamically predict relapse-free probability after alloHSCT, which would be a useful tool to provide important information to guide decision-making in the clinic and facilitate the individualized therapy.

Minimal residual disease in acute lymphoblastic leukemia: technical aspects and implications for clinical interpretation

Minimal residual disease (MRD) monitoring has proven to be one of the fundamental independent prognostic factors for patients with acute lymphoblastic leukemia (ALL). Sequential monitoring of MRD using sensitive and specific methods, such as real-time quantitative polymerase chain reaction (qPCR) or flow cytometry (FCM), has improved the assessment of treatment response and is currently used for therapeutic stratification and early detection. Although both FCM and qPCR yield highly consistent results with sensitivities of 10^‒4, each method has several limitations. For example, qPCR is time-consuming and laborious: designing primers that correspond to the immunoglobulin (IG) and T-cell receptor (TCR) gene rearrangements at diagnosis can take 3‒4 weeks. In addition, the evolution of additional clones beyond the first or index clone during therapy cannot be detected, which might lead to false-negative results. FCM requires experienced technicians and sometimes does not achieve a sensitivity of 10^‒4. Accordingly, a next generation sequencing (NGS)-based method has been developed in an attempt to overcome these limitations. With the advent of high-throughput NGS technologies, a more in-depth analysis of IG and/or TCR gene rearrangements is now within reach, which impacts all applications of IG/TR analysis. However, standardization, quality control, and validation of this new technology are warranted prior to its incorporation into routine practice.

Measurable residual disease of acute lymphoblastic leukemia in allograft settings: how to evaluate and intervene

INTRODUCTION

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a curable strategy for acute lymphoblastic leukemia (ALL), especially for adult cases. However, leukemia relapse after allograft restricts the improvement of transplant outcomes. Measurable residual disease (MRD) has been the strongest predictor for relapse after allo-HSCT, allowing MRD-directed preemptive therapy.

AREAS COVERED

This manuscript summarizes the detection of MRD in patients with ALL who undergo allo-HSCT, focusing the effects of positive pre-HSCT MRD and post-HSCT MRD on outcomes as well as MRD-directed interventions.

EXPERT OPINION

Except for MFC and RQ-PCR, other strategies, such as next-generation sequencing and RNAseq, have been developed for MRD determination. Negative effects of positive MRD peri-transplantation on outcomes of ALL patients were observed both in human leukocyte antigen (HLA)-matched sibling donor transplantation and in alternative donor transplantation. Advances have been made in determining the need for transplant according to MRD evaluation after induction or consolidation therapy. A number of approaches, including CAR-T-cell therapy, antibodies (blinatumomab, etc), targeted therapy (imatinib, etc), transplant donor selection, as well as donor lymphocyte infusion and interferon-α, have been successfully used or are promising for peri-transplantation MRD interventions. This progress could lead to the significant improvement of transplant outcomes for ALL patients.

Lack of Association Between Radiographic Tumor Burden and Efficacy of Immune Checkpoint Inhibitors in Advanced Lung Cancer

BACKGROUND

Historically, tumor burden has been considered an impediment to efficacy of immunotherapeutic agents, including vaccines, stem cell transplant, cytokine therapy, and intravesical bacillus Calmette-Guérin. This effect has been attributed to hypoxic zones in the tumor core contributing to poor T-cell infiltration, formation of immunosuppressive stromal cells, and development of therapy-resistant cell populations. However, the association between tumor burden and efficacy of immune checkpoint inhibitors is unknown. We sought to determine the association between radiographic tumor burden parameters and efficacy of immune checkpoint inhibitors in advanced lung cancer.

MATERIALS AND METHODS

We performed a retrospective analysis of patients with advanced lung cancer treated with immune checkpoint inhibitors. Demographic, disease, and treatment data were collected. Serial tumor dimensions were recorded according to RECIST version 1.1. Associations between radiographic tumor burden (baseline sum of longest diameters, longest single diameter) and clinical outcomes (radiographic response, progression-free survival, and overall survival) were determined using log-rank tests, Cox proportional-hazard regression, and logistic regression.

RESULTS

Among 105 patients, the median baseline sum of longest diameters (BSLD) was 6.4 cm; median longest single diameter was 3.6 cm. BSLD was not associated with best radiographic, progression-free survival, or overall survival. In univariate and multivariate analyses, no significant associations were observed for the other radiographic parameters and outcomes when considered as categorical or continuous variables.

CONCLUSION

Although tumor burden has been considered a mediator of efficacy of earlier immunotherapies, in advanced lung cancer it does not appear to affect outcomes from immune checkpoint inhibitors.

IMPLICATIONS FOR PRACTICE

Historically, tumor burden has been considered an impediment to the efficacy of various immunotherapies, including vaccines, cytokines, allogeneic stem cell transplant, and intravesical bacillus Calmette-Guérin. However, in the present study, no association was found between tumor burden and efficacy (response rate, progression-free survival, overall survival) of immune checkpoint inhibitors in advanced lung cancer. These findings suggest that immune checkpoint inhibitors may provide benefit across a range of disease burden, including bulky tumors considered resistant to other categories of immunotherapy.

Different Effects of Pre-transplantation Measurable Residual Disease on Outcomes According to Transplant Modality in Patients With Philadelphia Chromosome Positive ALL

Background: This study compared the effects of pre-transplantation measurable residual disease (pre-MRD) on outcomes in Philadelphia chromosome (Ph)-positive ALL patients who underwent human leukocyte antigen-matched sibling donor transplantation (MSDT) or who received unmanipulated haploidentical SCT (haplo-SCT). Methods: A retrospective study (n = 202) was performed. MRD was detected by RT-PCR and multiparameter flow cytometry. Results: In the total patient group, patients with positive pre-MRD had a higher 4-year cumulative incidence of relapse (CIR) than that in patients with negative pre-MRD (26.1% vs. 12.1%, P = 0.009); however, the cumulative incidence of non-relapse mortality (NRM) (7.4% vs. 15.9%, P = 0.148), probability of leukemia-free survival (LFS) (66.3% vs. 71.4%, P = 0.480), and overall survival (OS) (68.8% vs. 76.5%, P = 0.322) were comparable. In the MSDT group, patients with positive pre-MRD had increased 4-year CIR (56.4% vs. 13.8%, P < 0.001) and decreased 4-year LFS (35.9% vs. 71.0%, P = 0.024) and OS (35.9% vs. 77.6%, P = 0.011) compared with those with negative pre-MRD. In haplo-SCT settings, the 4-year CIR (14.8% vs. 10.7%, P = 0.297), NRM (7.3% vs. 16.3%, P = 0.187) and the 4-year probability of OS (77.7% vs. 72.3%, P = 0.804) and LFS (80.5% vs. 75.7%, P = 0.660) were comparable between pre-MRD positive and negative groups. In subgroup patients with positive pre-MRD, haplo-SCT had a lower 4-year CIR (14.8% vs. 56.4%, P = 0.021) and a higher 4-year LFS (77.7% vs. 35.9%, P = 0.036) and OS (80.5% vs. 35.9%, P = 0.027) than those of MSDT. Multivariate analysis showed that haplo-SCT was associated with lower CIR (HR, 0.288; P = 0.031), superior LFS (HR, 0.283; P = 0.019) and OS (HR, 0.252; P = 0.013) in cases with a positive pre-MRD subgroup. Conclusions: Our results indicate that the effects of positive pre-MRD on the outcomes of patients with Ph-positive ALL are different according to transplant modality. For Ph-positive cases with positive pre-MRD, haplo-SCT might have strong graft-vs.-leukemia (GVL) effects.

Monitoring minimal residual/relapsing disease after allogeneic haematopoietic stem cell transplantation in adult patients with acute lymphoblastic leukaemia

Relapse after allogeneic haematopoietic stem cell transplantation (SCT) is a major cause of death in patients with acute lymphoblastic leukaemia (ALL). Here, we retrospectively analysed the contributions of lineage-sorted donor cell chimerism (sDCC) and quantitative PCR (qPCR) targeting disease-specific genetic rearrangements to detect minimal residual/relapsing disease (MRD) and predict impending relapse in 94 adult ALL patients after SCT. With a median follow-up of surviving patients (n = 61) of 3.3 years, qPCR and/or sDCC measurements turned positive in 38 patients (40%). Of these, 22 patients relapsed and 16 remained in complete remission. At 3 years, qPCR and/or sDCC positive patients showed an increased incidence of relapse (50% vs. 4%, p < 0.0001), decreased relapse-free survival (RFS, 40% vs. 85%, p < 0.0001), and decreased overall survival (OS, 47% vs. 87%, p 0.004). Both, qPCR and sDCC pre-detected 11 of 21 relapses occurring within the first two years after SCT and, overall, complemented for each other method in four of the relapsing and four of the non-relapsing cases. Patients receiving pre-emptive MRD-driven interventions (n = 11) or not (n = 10) showed comparable median times until relapse, RFS, and OS. In our single centre cohort, qPCR and sDCC were similarly effective and complementary helpful to indicate haematological relapse of ALL after SCT.

Let's Talk About BiTEs and Other Drugs in the Real-Life Setting for B-Cell Acute Lymphoblastic Leukemia

Background: Therapy for acute lymphoblastic leukemia (ALL) are currently initially efficient, but even if a high percentage of patients have an initial complete remission (CR), most of them relapse. Recent data shows that immunotherapy with either bispecific T-cell engagers (BiTEs) of chimeric antigen receptor (CAR) T cells can eliminate residual chemotherapy-resistant B-ALL cells.

Objective: The objective of the manuscript is to present improvements in the clinical outcome for chemotherapy-resistant ALL in the real-life setting, by describing Romania's experience with bispecific antibodies for B-cell ALL.

Methods: We present the role of novel therapies for relapsed B-cell ALL, including the drugs under investigation in phase I-III clinical trials, as a potential bridge to transplant. Blinatumomab is presented in a critical review, presenting both the advantages of this drug, as well as its limitations.

Results: Bispecific antibodies are discussed, describing the clinical trials that resulted in its approval by the FDA and EMA. The real-life setting for relapsed B-cell ALL is described and we present the patients treated with blinatumomab in Romania.

Conclusion: In the current manuscript, we present blinatumomab as a therapeutic alternative in the bridge-to-transplant setting for refractory or relapsed ALL, to gain a better understanding of the available therapies and evidence-based data for these patients in 2019.

Clinical applications of donor lymphocyte infusion from an HLA-haploidentical donor: consensus recommendations from the Acute Leukemia Working Party of the EBMT

Donor lymphocyte infusion has been used in the management of relapsed hematologic malignancies after allogeneic hematopoietic cell transplantation. It can eradicate minimal residual disease or be used to rescue a hematologic relapse, being able to induce durable remissions in a subset of patients. With the increased use of haploidentical hematopoietic cell transplantation, there is renewed interest in the use of donor lymphocytes to either treat or prevent disease relapse post transplant. Published retrospective and small prospective studies have shown encouraging results with therapeutic donor lymphocyte infusion in different haploidentical transplantation platforms. In this consensus paper, finalized on behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation, we summarize the available evidence on the use of donor lymphocyte infusion from haploidentical donor, and provide recommendations on its therapeutic, pre-emptive and prophylactic use in clinical practice.

Blinatumomab for Acute Lymphoblastic Leukemia: The First Bispecific T-Cell Engager Antibody to Be Approved by the EMA for Minimal Residual Disease

On November 15, 2018, the Committee for Medicinal Products for Human Use (CHMP) recommended the extension of indication for blinatumomab to include the treatment of adults with minimal residual disease (MRD) positive B-cell precursor acute lymphoblastic leukemia (ALL). Blinatumomab was authorized to treat relapsed or refractory B-precursor ALL, and the change concerned an extension of use. On March 29, 2018, the U.S. Food and Drug Administration (FDA) granted accelerated approval to blinatumomab to treat both adults and children with B-cell precursor ALL who are in remission but still have MRD. On July 26, 2018, the CHMP had originally adopted a negative opinion on the extension. The reason for the initial refusal was that although blinatumomab helped to reduce the amount of residual cancer cells in many patients, there was no strong evidence that it led to improved survival. During the re-examination, the CHMP consulted the scientific advisory group. The CHMP agreed with the expert group's conclusion that, although there was no strong evidence of patients living longer, the available data from the main study (MT103-203) indicated a good durable response to blinatumomab, with an overall complete response rate for the primary endpoint full analysis set (defined as all subjects with an Ig or T-cell receptor polymerase chain reaction MRD assay with the minimum required sensitivity of 1 × 10^-4 at central lab established at baseline [n = 113]) as 79.6% (90/113; 95% confidence interval, 71.0-86.6), with a median time to complete MRD response of 29.0 days (range, 5-71). Therefore, the CHMP concluded that the benefits of blinatumomab outweigh its risks and recommended granting the change to the marketing authorization. The Committee for Orphan Medicinal Products, following reassessment, considered that significant benefit continued to be met and recommended maintaining the orphan designation and thus 10 years market exclusivity (the Orphan Designation is a legal procedure that allows for the designation of a medicinal substance with therapeutic potential for a rare disease, before its first administration in humans or during its clinical development). The marketing authorization holder for this medicinal product is Amgen Europe B.V. IMPLICATIONS FOR PRACTICE: Immunotherapy with blinatumomab has excellent and sustainable results, offering new hope for patients with minimal residual disease-positive acute lymphoblastic leukemia, a disease with poor prognosis. New recommendations and change of practice for treatment of this patient group are detailed.

Measurable residual disease at myeloablative allogeneic transplantation in adults with acute lymphoblastic leukemia: a retrospective registry study on 2780 patients from the acute leukemia working party of the EBMT

BACKGROUND

Assessment of measurable residual disease (MRD) is rapidly transforming the therapeutic and prognostic landscape of a wide range of hematological malignancies. Its prognostic value in acute lymphoblastic leukemia (ALL) has been established and MRD measured at the end of induction is increasingly used to guide further therapy. Although MRD detectable immediately before allogeneic hematopoietic cell transplantation (HCT) is known to be associated with poor outcomes, it is unclear if or to what extent this differs with different types of conditioning.

METHODS

In this retrospective registry study, we explored whether measurable residual disease (MRD) before allogeneic hematopoietic cell transplantation (HCT) for acute lymphoblastic leukemia is associated with different outcomes in recipients of myeloablative total body irradiation (TBI)-based versus chemotherapy-based conditioning. We analyzed outcomes of 2780 patients (median age 38 years, range 18-72) who underwent first HCT in complete remission between 2000 and 2017 using sibling or unrelated donors.

RESULTS

In 1816 of patients, no disease was detectable, and in 964 patients, MRD was positive. Conditioning was TBI-based in 2122 (76%) transplants. In the whole cohort MRD positivity was a significant independent factor for lower overall survival (OS) and leukemia-free survival (LFS), and for higher relapse incidence (RI), with respective hazard ratios (HR, 95% confidence intervals) of 1.19 (1.02-1.39), 1.26 (1.1-1.44), and 1.51 (1.26-1.8). TBI was associated with a higher OS, LFS, and lower RI with HR of 0.75 (0.62-0.90), 0.70 (0.60-0.82), and 0.60 (0.49-0.74), respectively. No significant interaction was found between MRD status and conditioning. When investigating the impact of MRD separately in the TBI and chemotherapy-based conditioning cohorts by multivariate analysis, we found MRD positivity to be associated with lower OS and LFS and higher RI in the TBI group, and with higher RI in the chemotherapy group. TBI-based conditioning was associated with improved outcomes in both MRD-negative and MRD-positive patients.

CONCLUSIONS

In this large study, we confirmed that patients who are MRD-negative prior to HCT achieve superior outcomes. This is particularly apparent if TBI conditioning is used. All patients with ALL irrespective of MRD status benefit from TBI-based conditioning in the myeloablative setting.

Minimal Residual Disease in Acute Lymphoblastic Leukemia: Technical and Clinical Advances

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 to guide therapeutic choices. The most standardized methods to study MRD in ALL are multi-parametric flow cytometry (MFC) and polymerase chain reaction (PCR) amplification-based methods. Emerging technologies hold the promise to improve MRD detection in ALL patients. Moreover, novel therapies, such as monoclonal antibodies, bispecific T-cell engagers, and chimeric antigen receptor T cells (CART) represent exciting advancements in the management of B-cell precursor (BCP)-ALL.

Aims: Through a review of the literature and in house data, we analyze the current status of MRD assessment in ALL to better understand how some of its limitations could be overcome by emerging molecular technologies. Furthermore, we highlight the future role of MRD monitoring in the context of personalized protocols, taking into account the genetic complexity in ALL.

Results and Conclusions: Molecular rearrangements (gene fusions and immunoglobulin and T-cell receptor-IG/TR gene rearrangements) are widely used as targets to detect residual leukemic cells in ALL patients. The advent of novel techniques, namely next generation flow cytometry (NGF), digital-droplet-PCR (ddPCR), and next generation sequencing (NGS) appear important tools to evaluate MRD in ALL, since they have the potential to overcome the limitations of standard approaches. It is likely that in the forthcoming future these techniques will be incorporated in clinical trials, at least at decisional time points. Finally, the advent of new powerful compounds is further increasing MRD negativity rates, with benefits in long-term survival and a potential reduction of therapy-related toxicities. However, the prognostic relevance in the setting of novel immunotherapies still needs to be evaluated.

Minimal residual disease status determined by multiparametric flow cytometry pretransplantation predicts the outcome of patients with ALL receiving unmanipulated haploidentical allografts

This study evaluated the effects of pretransplantation minimal residual disease (pre-MRD) on outcomes of patients with acute lymphoblastic leukemia (ALL) who underwent unmanipulated haploidentical stem cell transplantation (haplo-SCT). A retrospective study including 543 patients with ALL was performed. MRD was determined using multiparametric flow cytometry. Both in the entire cohort of patients and in subgroup cases with T-ALL or B-ALL, patients with positive pre-MRD had a higher incidence of relapse (CIR) than those with negative pre-MRD in MSDT settings (P < 0.01 for all). Landmark analysis at 6 months showed that MRD positivity was significantly and independently associated with inferior rates of relapse (HR, 1.908; P = 0.007), leukemia-free survival (LFS) (HR, 1.559; P = 0.038), and OS (HR, 1.545; P = 0.049). The levels of pre-MRD according to a logarithmic scale were also associated with leukemia relapse, LFS, and OS, except that cases with MRD <0.01% experienced comparable CIR and LFS to those with negative pre-MRD. A risk score for CIR was developed using the variables pre-MRD, disease status, and immunophenotype of ALL. The CIR was 14%, 26%, and 59% for subjects with scores of 0, 1, and 2-3, respectively (P < 0.001). Three-year LFS was 75%, 64%, and 42%, respectively (P < 0.001). Multivariate analysis confirmed the association of the risk score with CIR and LFS. The results indicate that positive pre-MRD, except for low level one (MRD < 0.01%), is associated with poor outcomes in patients with ALL who underwent unmanipulated haplo-SCT.

Prognostic significance of CDKN2A/B deletions in acute lymphoblastic leukaemia: a meta-analysis

BACKGROUND

Cyclin-dependent kinase inhibitor 2A/B (CDKN2A/B) genes are frequently altered in acute lymphoblastic leukaemia (ALL) patients. The aim of this meta-analysis was to comprehensively assess the prognostic value of CDKN2A/B deletions in ALL patients.

METHODS

Systematic literature review was conducted in PubMed, Embase and Cochrane databases up to July 2018. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated with fixed-effects or random-effects models.

RESULTS

A total of thirteen studies including 2857 patients were eligible for this meta-analysis. Combined HRs suggested that CDKN2A/B deletions were poor prognostic factors for both overall survival (OS) (HR = 2.15, 95% CI 1.82-2.54) and event-free survival (EFS)/disease-free survival (DFS)/relapse-free survival (RFS) (HR = 2.16, 95% CI 1.73-2.69). The adverse impact remained significant in both adult and paediatric ALL patients, and also in subgroups by ethnicity, ALL type, detection method of CDKN2A/B deletions, statistical method and endpoint.

CONCLUSIONS

Our findings suggested that CDKN2A/B deletions were associated with poor prognosis independently in both adult and childhood ALL patients. Inclusion of CDKN2A/B status may further improve the risk stratification of ALL patients. Key Messages Although numerous studies have explored the prognostic significance of cyclin-dependent kinase inhibitor 2A/B (CDKN2A/B) deletions in acute lymphoblastic leukaemia (ALL) patients, the results remain conflicting. In this meta-analysis, we found that CDKN2A/B deletions were independent poor prognostic markers for both adult and paediatric ALL patients. Our findings justify the inclusion of CDKN2A/B status in the risk stratification of ALL patients.