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

Therapeutic targeting of KSP in preclinical models of high-risk neuroblastoma

Neuroblastoma is a childhood malignancy with often dismal prognosis; relapse is common despite intense treatment. Here, we used human tumor organoids representing multiple MYCN-amplified high-risk neuroblastomas to perform a high-throughput drug screen with approved or emerging oncology drugs. Tumor-selective effects were calculated using drug sensitivity scores. Several drugs with previously unreported anti-neuroblastoma effects were identified by stringent selection criteria. ARRY-520, an inhibitor of kinesin spindle protein (KSP), was among those causing reduced viability. High expression of the KSP-encoding gene KIF11 was associated with poor outcome in neuroblastoma. Genome-scale loss-of-function screens in hundreds of human cancer cell lines across 22 tumor types revealed that KIF11 is particularly important for neuroblastoma cell viability. KSP inhibition in neuroblastoma patient-derived xenograft (PDX) cells resulted in the formation of abnormal monoastral spindles, mitotic arrest, up-regulation of mitosis-associated genes, and apoptosis. In vivo, KSP inhibition caused regression of MYCN-amplified neuroblastoma PDX tumors. Furthermore, treatment of mice harboring orthotopic neuroblastoma PDX tumors resulted in increased survival. Our results suggested that KSP inhibition could be a promising treatment strategy in children with high-risk neuroblastoma.

Indications for Allogeneic HCT in Adults with Acute Lymphoblastic Leukemia in First Complete Remission

OPINION STATEMENT

Acute lymphoblastic leukemia (ALL) in adults is associated with poor outcomes as compared to children when treated with chemotherapy, leading to a considerably inferior cure rate. Historically, consolidation with allogeneic hematopoietic cell transplant (alloHCT) was routinely recommended for eligible adults with ALL in first complete remission (CR1) if a donor was available, since randomized studies showed superiority over continuing chemotherapy. With the increasing use of pediatric-inspired frontline regimens in young adults with ALL and the availability of novel salvage agents for relapsed/refractory B-cell ALL that have high potential in inducing a second CR, the role of early alloHCT in the treatment paradigm for ALL needs to be reevaluated, and the decision should be individualized for each patient. Simultaneously, alloHCT has evolved considerably lately, and historical randomized studies that have proven the benefit of alloHCT in adults with ALL in CR1 did not included the increasing use of reduced intensity conditioning and haploidentical transplants, and therefore, data may not entirely apply. Nowadays, detectable minimal residual disease (MRD) is the most prognostic determinant of ALL outcome and should be a major consideration in the decision to perform alloHcT in CR1. Nonetheless, other biological and clinical factors remain relevant and can support the complex decision-making. Such factors include high-risk leukemia genetics, the type of administered chemotherapy regimen and the ability of the patient to tolerate all key components of the regimen, and the availability of effective salvage therapies that allow alloHCT to be performed in CR2 in case of relapse after chemotherapy.

Outcomes and prognostic factors in adolescents and young adults with ALL treated with a modified BFM-90 protocol

The use of pediatrics-inspired protocols in adolescent and young adult (AYA) acute lymphoblastic leukemia (ALL) results in superior survival compared with the adult protocols. Pediatrics-inspired protocols carry an increased risk of toxicity and treatment-related mortality in low resource settings, which can offset the potential benefits. We studied the outcomes and prognostic factors in the treatment of AYA ALL with a pediatrics-inspired regimen. We retrieved data regarding demographics, investigations, treatment details, and toxicities from the electronic medical records of patients diagnosed with ALL in the 15- to 25-year-old age group who were initiated on a modified Berlin-Frankfurt-Münster 90 (BFM-90) protocol between January 2013 and December 2016 at the Tata Memorial Centre. A total of 349 patients in the 15- to 25-year-old age group were treated with a modified BFM-90 protocol. The use of this pediatrics-inspired protocol resulted in a 3-year event-free survival (EFS) and overall survival (OS) of 59.4% and 61.8%, respectively. Only 15 patients underwent an allogeneic stem cell transplant. Minimal residual disease (MRD) persistence postinduction emerged as the only factor predictive of poor outcomes. A modified BFM-90 protocol is an effective and safe regimen for AYA ALL with an OS and EFS comparable to the published literature.

Integrating CAR T-Cell Therapy and Transplantation: Comparisons of Safety and Long-Term Efficacy of Allogeneic Hematopoietic Stem Cell Transplantation After CAR T-Cell or Chemotherapy-Based Complete Remission in B-Cell Acute Lymphoblastic Leukemia

Patients often undergo consolidation allogeneic hematopoietic stem cell transplantation (allo-HSCT) to maintain long-term remission following chimeric antigen receptor (CAR) T-cell therapy. Comparisons of safety and efficacy of allo-HSCT following complete remission (CR) achieved by CAR-T therapy versus by chemotherapy for B-cell acute lymphoblastic leukemia (B-ALL) has not been reported. We performed a parallel comparison of transplant outcomes in 105 consecutive B-ALL patients who received allo-HSCT after achieving CR with CAR-T therapy (n=27) or with chemotherapy (n=78). The CAR-T-allo-HSCT group had more patients in second CR compared to the chemotherapy-allo-HSCT group (78% vs. 37%; p<0.01) and more with complex cytogenetics (44% vs. 6%; p<0.001) but the proportion of patients with pre-transplant minimal residual disease (MRD) was similar. The median follow-up time was 49 months (range: 25-54 months). The CAR-T cohort had a higher incidence of Grade II-IV acute graft-versus-host disease (aGVHD 48.1% [95% CI: 46.1-50.1%] vs. 25.6% [95%CI: 25.2-26.0%]; p=0.016). The incidence of Grade III-IV aGVHD was similar in both groups (11.1% vs.11.5%, p=0.945). The overall incidence of chronic GVHD in the CAR-T group was higher compared to the chemotherapy group (73.3% [95%CI: 71.3-75.3%] vs. 55.0% [95%CI: 54.2-55.8%], p=0.107), but the rate of extensive chronic GVHD was similar (11.1% vs.11.9%, p=0.964). Efficacy measures 4 years following transplant were all similar in the CAR-T vs. the chemotherapy groups: cumulative incidences of relapse (CIR; 11.1% vs.12.8%; p=0.84), cumulative incidences of non-relapse mortality (NRM; 18.7% vs. 23.1%; p=0.641) leukemia-free survival (LFS; 70.2% vs. 64.1%; p=0.63) and overall survival (OS; 70.2% vs. 65.4%; p=0.681). We found that pre-transplant MRD-negative CR predicted a lower CIR and a higher LFS compared with MRD-positive CR. In conclusion, our data indicate that, in B-ALL patients, similar clinical safety outcomes could be achieved with either CD19 CAR T-cell therapy followed by allo-HSCT or chemotherapy followed by allo-HSCT. Despite the inclusion of more patients with advanced diseases in the CAR-T group, the 4-year LFS and OS achieved with CAR T-cells followed by allo-HSCT were as remarkable as those achieved with chemotherapy followed by allo-HSCT. Further confirmation of these results requires larger, randomized clinical trials.

Oncogenetic landscape and clinical impact of IDH1 and IDH2 mutations in T-ALL

IDH1 and IDH2 mutations (IDH1/2^Mut) are recognized as recurrent genetic alterations in acute myeloid leukemia (AML) and associated with both clinical impact and therapeutic opportunity due to the recent development of specific IDH1/2^Mut inhibitors. In T-cell acute lymphoblastic leukemia (T-ALL), their incidence and prognostic implications remain poorly reported. Our targeted next-generation sequencing approach allowed comprehensive assessment of genotype across the entire IDH1 and IDH2 locus in 1085 consecutive unselected and newly diagnosed patients with T-ALL and identified 4% of, virtually exclusive (47 of 49 patients), IDH1/2^Mut. Mutational patterns of IDH1/2^Mut in T-ALL present some specific features compared to AML. Whereas IDH2^R140Q mutation was frequent in T-ALL (25 of 51 mutations), the IDH2^R172 AML hotspot was absent. IDH2 mutations were associated with older age, an immature phenotype, more frequent RAS gain-of-function mutations and epigenetic regulator loss-of-function alterations (DNMT3A and TET2). IDH2 mutations, contrary to IDH1 mutations, appeared to be an independent prognostic factor in multivariate analysis with the NOTCH1/FBXW7/RAS/PTEN classifier. IDH2^Mut were significantly associated with a high cumulative incidence of relapse and very dismal outcome, suggesting that IDH2-mutated T-ALL cases should be identified at diagnosis in order to benefit from therapeutic intensification and/or specific IDH2 inhibitors.

Chemotherapy or allogeneic transplantation in high-risk Philadelphia chromosome-negative adult lymphoblastic leukemia

The need for allogeneic hematopoietic stem cell transplantation (allo-HSCT) in adults with Philadelphia chromosome-negative (Ph-) acute lymphoblastic leukemia (ALL) with high-risk (HR) features and adequate measurable residual disease (MRD) clearance remains unclear. The aim of the ALL-HR-11 trial was to evaluate the outcomes of HR Ph- adult ALL patients following chemotherapy or allo-HSCT administered based on end-induction and consolidation MRD levels. Patients aged 15 to 60 years with HR-ALL in complete response (CR) and MRD levels (centrally assessed by 8-color flow cytometry) <0.1% after induction and <0.01% after early consolidation were assigned to receive delayed consolidation and maintenance therapy up to 2 years in CR. The remaining patients were allocated to allo-HSCT. CR was attained in 315/348 patients (91%), with MRD <0.1% after induction in 220/289 patients (76%). By intention-to-treat, 218 patients were assigned to chemotherapy and 106 to allo-HSCT. The 5-year (±95% confidence interval) cumulative incidence of relapse (CIR), overall survival (OS), and event-free survival probabilities for the whole series were 43% ± 7%, 49% ± 7%, and 40% ± 6%, respectively, with CIR and OS rates of 45% ± 8% and 59% ± 9% for patients assigned to chemotherapy and of 40% ± 12% and 38% ± 11% for those assigned to allo-HSCT, respectively. Our results show that avoiding allo-HSCT does not hamper the outcomes of HR Ph- adult ALL patients up to 60 years with adequate MRD response after induction and consolidation. Better postremission alternative therapies are especially needed for patients with poor MRD clearance. This trial was registered at www.clinicaltrials.gov as # NCT01540812.

Consensus Recommendations for MRD Testing in Adult B-Cell Acute Lymphoblastic Leukemia in Ontario

Measurable (minimal) residual disease (MRD) is an established, key prognostic factor in adult B-cell acute lymphoblastic leukemia (B-ALL), and testing for MRD is known to be an important tool to help guide treatment decisions. The clinical value of MRD testing depends on the accuracy and reliability of results. Currently, there are no Canadian provincial or national guidelines for MRD testing in adult B-ALL, and consistent with the absence of such guidelines, there is no uniform Ontario MRD testing consensus. Moreover, there is great variability in Ontario in MRD testing with respect to where, when, and by which technique, MRD testing is performed, as well as in how the results are interpreted. To address these deficiencies, an expert multidisciplinary working group was convened to define consensus recommendations for improving the provision of such testing. The expert panel recommends that MRD testing should be implemented in a centralized manner to ensure expertise and accuracy in testing for this low volume indication, thereby to provide accurate, reliable results to clinicians and patients. All adult patients with B-ALL should receive MRD testing after induction chemotherapy. Philadelphia chromosome (Ph)-positive patients should have ongoing monitoring of MRD during treatment and thereafter, while samples from Ph-negative B-ALL patients should be tested at least once later during treatment, ideally at 12 to 16 weeks after treatment initiation. In Ph-negative adult B-ALL patients, standardized, ideally centralized, protocols must be used for MRD testing, including both flow cytometry and immunoglobulin (Ig) heavy chain and T-cell receptor (TCR) gene rearrangement analysis. For Ph-positive B-ALL patients, MRD testing using a standardized protocol for reverse transcription real-time quantitative PCR (RT-qPCR) for the BCR-ABL1 gene fusion transcript is recommended, with Ig/TCR gene rearrangement analysis done in parallel likely providing additional clinical information.

The impact of phenotypic heterogeneity of tumour cells on treatment and relapse dynamics

Intratumour heterogeneity is increasingly recognized as a frequent problem for cancer treatment as it allows for the evolution of resistance against treatment. While cancer genotyping becomes more and more established and allows to determine the genetic heterogeneity, less is known about the phenotypic heterogeneity among cancer cells. We investigate how phenotypic differences can impact the efficiency of therapy options that select on this diversity, compared to therapy options that are independent of the phenotype. We employ the ecological concept of trait distributions and characterize the cancer cell population as a collection of subpopulations that differ in their growth rate. We show in a deterministic model that growth rate-dependent treatment types alter the trait distribution of the cell population, resulting in a delayed relapse compared to a growth rate-independent treatment. Whether the cancer cell population goes extinct or relapse occurs is determined by stochastic dynamics, which we investigate using a stochastic model. Again, we find that relapse is delayed for the growth rate-dependent treatment type, albeit an increased relapse probability, suggesting that slowly growing subpopulations are shielded from extinction. Sequential application of growth rate-dependent and growth rate-independent treatment types can largely increase treatment efficiency and delay relapse. Interestingly, even longer intervals between decisions to change the treatment type may achieve close-to-optimal efficiencies and relapse times. Monitoring patients at regular check-ups may thus provide the temporally resolved guidance to tailor treatments to the changing cancer cell trait distribution and allow clinicians to cope with this dynamic heterogeneity.

The individual cells within a cancer cell population are not all equal. The heterogeneity among them can strongly affect disease progression and treatment success. Recent diagnostic advances allow measuring how the characteristics of this heterogeneity change over time. To match these advances, we developed deterministic and stochastic trait-based models that capture important characteristics of the intratumour heterogeneity and allow to evaluate different treatment types that either do or do not interact with this heterogeneity. We focus on growth rate as the decisive characteristic of the intratumour heterogeneity. We find that by shifting the trait distribution of the cancer cell population, the growth rate-dependent treatment delays an eventual relapse compared to the growth rate-independent treatment. As a downside, however, we observe a refuge effect where slower-growing subpopulations are less affected by the growth rate-dependent treatment, which may decrease the likelihood of successful therapy. We find that navigating along this trade-off may be achieved by sequentially combining both treatment types, which agrees qualitatively with current clinical practice. Interestingly, even rather large intervals between treatment changes allow for close-to-optimal treatment results, which again hints towards a practical applicability.

Recent Advances in Managing Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is characterized by chromosomal translocations and somatic mutations that lead to leukemogenesis. The incorporation of pediatric-type regimens has improved survival in young adults, and the incorporation of tyrosine kinase inhibitors for patients with Philadelphia chromosome-positive disease has led to further improvements in outcomes. However, older patients often have poor-risk biology and reduced tolerance to chemotherapy, leading to lower remission rates and overall survival. Regardless of age, patients with relapsed or refractory ALL have extremely poor outcomes. The advent of next-generation sequencing has facilitated the revolution in understanding the genetics of ALL. New genetic risk stratification together with the ability to measure minimal residual disease, leukemic blasts left behind after cytotoxic chemotherapy, has led to better tools to guide postremission approaches-that is, consolidation chemotherapy or allogeneic stem cell transplantation. In this article, we discuss the evolving and complex genetic landscape of ALL and the emerging therapeutic options for patients with relapsed/refractory ALL and older patients with ALL.

How to Combine the Two Landmark Treatment Methods-Allogeneic Hematopoietic Stem Cell Transplantation and Chimeric Antigen Receptor T Cell Therapy Together to Cure High-Risk B Cell Acute Lymphoblastic Leukemia?

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has made tremendous progress in the last few decades and is increasingly being used worldwide. The success of haploidentical HSCT has made it possible to have "a donor for everyone". Patients who received transplantation in remission may have a favorable outcome, while those who were transplanted in advanced stages of disease have a poor prognosis. Although chimeric antigen receptor T (CAR-T) cell therapy is currently a milestone in the immunotherapy of relapsed or refractory (R/R) B cell acute lymphoblastic leukemia (B-ALL) and has demonstrated high remission rates in patients previously treated in multiple lines, the relatively high relapse rate remains a barrier to CAR-T cell therapy becoming an excellent cure option. Therefore, combining these two approaches (allo-HSCT and CAR-T cell therapy) is an attractive area of research to further improve the prognosis of R/R B-ALL. In this review, we will discuss the current clinical practices of combining allo-HSCT with CAR-T cell therapy based on available data, including CAR-T cells as a bridge to allo-HSCT for R/R B-ALL and CAR-T cell infusion for post-transplant relapse. We will further explore not only other possible ways to combine the two approaches, including CAR-T cell therapy to clear minimal residual disease peri-transplantation and incorporation of CAR technology to treat graft-versus-host disease, but also the potential of CAR-T cells as a part of allo-HSCT.

Value of flow cytometry for MRD-based relapse prediction in B-cell precursor ALL in a multicenter setting

PCR of TCR/Ig gene rearrangements is considered the method of choice for minimal residual disease (MRD) quantification in BCP-ALL, but flow cytometry analysis of leukemia-associated immunophenotypes (FCM-MRD) is faster and biologically more informative. FCM-MRD performed in 18 laboratories across seven countries was used for risk stratification of 1487 patients with BCP-ALL enrolled in the NOPHO ALL2008 protocol. When no informative FCM-marker was available, risk stratification was based on real-time quantitative PCR. An informative FCM-marker was found in 96.2% and only two patients (0.14%) had non-informative FCM and non-informative PCR-markers. The overall 5-year event-free survival was 86.1% with a cumulative incidence of relapse (CIR_5y) of 9.5%. FCM-MRD levels on days 15 (HzR 4.0, p < 0.0001), 29 (HzR 2.7, p < 0.0001), and 79 (HzR 3.5, p < 0.0001) associated with hazard of relapse adjusted for age, cytogenetics, and WBC. The early (day 15) response associated with CIR_5y adjusted for day 29 FCM-MRD, with higher levels in adults (median 2.4 × 10⁻² versus 5.2 × 10⁻³, p < 0.0001). Undetectable FCM- and/or PCR-MRD on day 29 identified patients with a very good outcome (CIR_5y = 3.2%). For patients who did not undergo transplantation, day 79 FCM-MRD > 10⁻⁴ associated with a CIR_5y = 22.1%. In conclusion, FCM-MRD performed in a multicenter setting is a clinically useful method for MRD-based treatment stratification in BCP-ALL.

Impact of Novel Targeted Therapies and Cytogenetic Risk Groups on Outcome After Allogeneic Transplantation for Adult ALL

Novel high-risk groups have recently been identified in adult acute lymphoblastic leukemia (ALL), including Philadelphia-like, therapy-related, and measurable residual disease after induction therapy. Furthermore, modern targeted therapies have recently been incorporated into ALL management; rituximab for CD20-positive and blinatumomab for measurable residual disease after induction therapy or relapsed or refractory disease. Allogeneic hematopoietic cell transplantation (allo-HCT) is recommended as consolidation therapy for high-risk ALL; however, its relative benefit for these high-risk groups and after novel therapies is unclear. We performed an analysis of posttransplantation outcomes in a cohort of 261 consecutive patients who underwent allo-HCT for ALL at the 3-site Mayo Clinic Cancer Center (January 1, 2008-December 31, 2018). With a median (range) follow-up of 22.4 months (0.5-135.0), the 100-day and 5-year cumulative incidences of nonrelapse mortality rates were 6.5% and 26.7%, respectively. The 5-year cumulative incidences of relapse and death were 22.6% and 46.2%, respectively. The 1-year estimate of the composite endpoint of graft-versus-host disease/relapse-free survival was 39.3%. We observed no associations of novel high-risk groups or modern targeted therapies with overall survival, nonrelapse mortality, or relapse in multivariable analysis. An increased risk of relapse was observed with T-ALL (hazard ratio, 2.16; 95% confidence interval, 1.14-4.09; P = .02) and hypodiploidy/near-triploidy (hazard ratio, 2.84; 95% confidence interval, 1.06-7.62; P = .04). Our analysis suggests that novel high-risk groups derive a similar benefit from allo-HCT as traditional high-risk adult ALL and that novel targeted therapies do not seem to independently predict for posttransplantation outcomes. It also calls for further exploration of maintenance strategies after Allo-HCT to prevent relapse in high-risk subgroups.

New approaches to the treatment of older adults with acute lymphoblastic leukemia

Outcomes for older adults (defined here as ≥55-65 years old) with acute lymphoblastic leukemia (ALL) are poor, with long-term survival less than 20%. Pediatric chemotherapy regimens produce long-term cure rates of 80% to 90% in children and 60% to 70% in adolescents and young adults with Ph-negative ALL, however, tolerability of intensive chemotherapy becomes problematic with advanced age due to comorbidities and reduced tolerability of chemotherapy leading to high rates of treatment-related mortality. For older adults with Ph-positive ALL, BCR-ABL1-directed tyrosine kinase inhibitors in combination with corticosteroids or chemotherapy produce deep remissions with low treatment-related toxicity but optimal postremission therapy is not known. New therapeutic approaches for older adults with ALL involve integration of the novel targeted agents including monoclonal antibody-based therapy with blinatumomab and inotuzumab ozogamicin in the frontline. Ongoing studies will ideally define optimal combinations and sequencing of novel agents with or without chemotherapy, tyrosine kinase inhibitors, and/or corticosteroids to maximize efficacy while avoiding treatment-related death. Anti-CD19 chimeric antigen receptor modified T cells are a promising modality, with high rates of remission and minimal residual disease negativity achieved in early phase trials for adults with relapsed/refractory B-cell ALL but the tolerability of chimeric antigen receptor modified T cell therapies in older adults is yet to be well defined. Advances in minimal residual disease detection have helped to effectively stratify adults in complete response in terms of relapse risk and predicted relative benefit for allogeneic hematopoietic cell transplant. For older adults with ALL in complete response at high risk for relapse for whom myeloablative conditioning is predicted to result in excessive transplant-related mortality, reduced-intensity conditioning allogeneic hematopoietic cell transplant is a less toxic approach for providing a graft-versus-leukemia effect and long-term disease control.

Measurable Residual Disease Assessment and Allogeneic Transplantation as Consolidation Therapy in Adult Acute Lymphoblastic Leukemia in Colombia

INTRODUCTION

Detectable minimal residual disease (MRD) after therapy for acute lymphoblastic leukemia (ALL) is the strongest predictor of hematologic relapse. The objective of the study was to assess disease-free survival (DFS) and overall survival (OS) of patients with ALL according with MRD status at the end of induction therapy in a Colombian population.

PATIENTS AND METHODS

We assessed a retrospective cohort to compare DFS and OS in adults with de novo ALL according to MRD status at the end of induction chemotherapy, and the type of postinduction consolidation strategy used.

RESULTS

A total of 165 adults with ALL were included in the MRD part of the study, 73 patients in the MRD-negative group and 92 in the MRD-positive group. Median DFS for the MRD-positive group was 11 months (95% confidence interval, 11.7-22.2) and was not reached for the MRD-negative group (P < .001). At 3 years, DFS was 18% and 55%, respectively (P < .001). The median OS for MRD-positive patients was 16 months (95% confidence interval, 8.8-23.15) and was not reached in the MRD-negative group. At 3 years, OS was 26% and 51% for the former and latter group, respectively. Among subjects who did not receive a transplant, median DFS was 21 months for MRD-negative patients and 9 months for MRD-positive patients (P < .001). The median DFS was not reached in either group, whereas 3-year DFS was 64% for MRD-negative and 70% for MRD-positive patients who underwent transplantation in first remission (P = .861).

CONCLUSION

MRD status at the end of induction is an independent prognostic factor for DFS and OS in adult ALL. Allogeneic transplantation in first remission could overcome the adverse prognostic impact of MRD.

Updated risk-oriented strategy for acute lymphoblastic leukemia in adult patients 18-65 years: NILG ALL 10/07

An updated strategy combining pediatric-based chemotherapy with risk-oriented allogeneic hematopoietic cell transplantation (HCT) was evaluated in Philadelphia chromosome-negative acute lymphoblastic leukemia (Ph- ALL) and compared with a published control series. Following induction-consolidation chemotherapy, responsive patients were assigned to receive maintenance chemotherapy or undergo early HCT according to the risk stratification criteria and minimal residual disease (MRD) status. Of the 203 study patients (median age 41 years, range 17-67), 140/161 with Ph- ALL achieved complete remission (86.9%; 91.6% ≤55 years, P = 0.0002), with complete MRD clearing in 68/109; 55 patients were assigned to maintenance chemotherapy, and 85 to HCT due to very high-risk characteristics (hyperleukocytosis, adverse genetics, early/mature T-precursor ALL, and MRD persistence). The 5-year relapse incidence was 36%, and the treatment-related mortality rate was 18%. Median overall and relapse-free survival were 7.4 and 6.2 years, with rates of 54 and 53% at 5 years, respectively, which were significantly better than those obtained with the historical protocol (P = 0.001 and P = 0.005, respectively), without significant differences between maintenance and HCT cohorts. In prognostic analysis, MRD negativity and age ≤55 years were the most favorable independent prognostic factors. A reduction in treatment toxicity and further improvements in the risk definitions and risk-oriented design are the focuses of this ongoing research.

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.

Outcome predictors after retransplantation in relapsed acute lymphoblastic leukemia: a multicenter, retrospective study

Retransplantation is the only curative treatment option for patients with acute lymphoblastic leukemia (ALL) that has relapsed after allogeneic hematopoietic cell transplantation (allo-HCT); however, data in this setting remain scant. Hence, this multicenter, retrospective study aims to determine outcome predictors after retransplantation in relapsed ALL. We examined 55 recipients who underwent multiple allo-HCTs during 2006-2018. The 2-year overall survival (OS), progression-free survival (PFS), and non-relapse mortality rates were 35.9%, 29.1%, and 23.6%, respectively. We observed a trend of better outcome in Ph + ALL (n = 22) patients compared with non-Ph ALL (n = 33) patients; the 2-year PFS was 40.9% versus 21.2%, indicating a beneficial effect of more potent second- or third-generation tyrosine kinase inhibitors. Univariate analysis revealed that late relapse after the previous transplant was the only significant predictor of better transplant outcome among Ph + ALL patients, whereas factors related to prolonged OS/PFS in non-Ph ALL patients were late relapse after the previous transplant, longer duration from disease relapse/progression to second or more allo-HCT, disease status at the transplantation, and good performance status. Nevertheless, further investigations are warranted to determine whether novel molecular-targeted agents with higher efficacy and fewer toxicities could exceed conventional chemotherapies as a bridging strategy to next allo-HCT and improve the outcomes of non-Ph ALL patients.

Evaluating Blinatumomab for the Treatment of Relapsed/Refractory ALL: Design, Development, and Place in Therapy

Although adults with B-cell acute lymphoblastic leukemia (B-ALL) achieve high complete remission (CR) rates following treatment with intensive multi-agent chemotherapy regimens, up to two-thirds of these patients eventually relapse. Unfortunately, adults with relapsed or refractory (R/R) B-ALL have a poor prognosis, with variable responses to salvage chemotherapy regimens and allogeneic stem cell transplant. As such, the need to develop effective and well-tolerated treatments for this patient population has been of paramount importance over the past decade. In this regard, treatment options for R/R B-ALL patients have expanded considerably over a relatively short period of time, with the approvals of blinatumomab, inotuzumab ozogamicin and tisagenlecleucel occurring within only the past six years. Blinatumomab, a CD19 x CD3 bispecific T-cell engager (BiTE) was the first of these immune therapies to receive approval, and for many patients, is used as first-line salvage therapy. A number of large clinical trials have demonstrated improved progression-free survival and overall survival for R/R B-ALL patients receiving blinatumomab as compared to those receiving conventional salvage chemotherapy. In addition to being approved for both Philadelphia chromosome-negative and Philadelphia chromosome-positive R/R B-ALL, blinatumomab is also the only ALL therapy that carries approval for the treatment of measurable residual disease (MRD). Although blinatumomab has changed the therapeutic landscape for adults with R/R B-ALL, a number of important clinical considerations and questions remain, including the potential role of blinatumomab in the frontline setting, mechanisms of resistance, optimal goal MRD level, the role of transplant following MRD clearance, the optimal place for blinatumomab in the context of other recently approved immune-mediated therapies, and real world outcomes for patients treated outside the context of clinical trials. These issues are the focus of ongoing studies, which will hopefully inform future clinical practice regarding the utility of blinatumomab in the treatment of B-ALL patients.

Prognostic factors for survival after allogeneic transplantation in acute lymphoblastic leukemia

Allogeneic stem cell transplantation (allo-SCT) offers a curative option in adult patients with acute lymphoblastic leukemia (ALL). Prognostic factors for survival after allo-SCT have not been sufficiently defined: pheno-/genotype, patients´ age, conditioning regimens and remission at allo-SCT are under discussion. We analyzed the outcome of 180 consecutive adult ALL-patients undergoing allo-SCT at our center between 1995 and 2018 to identify specific prognostic factors. In our cohort 19% were older than 55 years, 28% had Philadelphia-positive B-ALL, 24% T-ALL. 54% were transplanted in first complete remission (CR1), 13% in CR2 after salvage therapy, 31% reached no remission (8% within first-line, 23% within salvage therapy). In 66% conditioning contained total body irradiation (TBI). With a median follow-up of 10 years, we observed an overall survival of 33% at 10 years, and a progression free survival of 31%. The cumulative incidence of relapse was 41% at 10 years, the cumulative incidence of non-relapse mortality 28%. Acute graft-versus-host disease (GvHD) II°-IV° occurred in 31%, moderate/severe chronic GvHD in 27%. Survival was better in patients reaching CR before allo-SCT and in those receiving TBI. No difference between patients younger/older than 55 years and between different phenotypes was observed. Survival after allo-SCT improved considerably over the last decades.

Treatment and outcome of Philadelphia chromosome-positive acute lymphoblastic leukemia in adults after relapse

INTRODUCTION

Despite the significant progress that has been made over the last years in the front-line treatment of Philadelphia (Ph) chromosome-positive acute lymphoblastic leukemia (ALL), relapses are frequent and their treatment remains a challenge, especially among patients with resistant BCR-ABL1 mutations.

AREAS COVERED

This manuscript reviews available data for the treatment of adult patients with relapsed/refractory Ph-positive ALL, with a focus on the role of tyrosine kinase inhibitors (TKIs), monoclonal antibodies, and immunotherapy.

EXPERT OPINION

Although a majority of patients with first relapsed Ph-positive ALL respond to subsequent salvage chemotherapy plus TKI combination, their outcomes remain poor. The main predictor of survival is the achievement of major molecular response anytime during the morphological response. More treatment strategies to improve survival are under investigation. Monoclonal antibodies and bispecific antibody constructs hold considerable promise in improving the outcomes of patients with relapsed ALL including Ph-positive ALL.

Bispecific antibodies in acute lymphoblastic leukemia therapy

INTRODUCTION

Blinatumomab, first in a class of bispecific T-cell engagers, revolutionized treatment paradigm of B-cell precursor relapsed/refractory or minimal residual disease positive acute lymphoblastic leukemia (ALL) in adults and children, inducing deep remissions in a proportion of patients. However, significant numbers of patients do not respond or eventually relapse. Strategies for improvement of treatment outcomes are required.

AREAS COVERED

This review discusses the main structural and functional features of blinatumomab, and its place in the treatment of ALL. Furthermore, prospects to increase the efficacy of blinatumomab are addressed. The developments in the field of bispecific antibodies and their possible implications for treatment of ALL are reviewed.

EXPERT OPINION

Better understanding the mechanisms of response and resistance to blinatumomab might help us to identify the group of patients benefiting most from treatment and to spare potentially toxic subsequent treatment strategies. Data emerging from ongoing clinical trials might change the treatment landscape of ALL and beyond. Early use of blinatumomab in frontline protocols with more advantageous treatment sequences and in combination with other targeted therapies might reduce the failure rates. Exponentially increasing number of novel treatment options and their possible combinations might complicate treatment decision-making without data from randomized trials.

Managing toxicities with asparaginase-based therapies in adult ALL: summary of an ESMO Open-Cancer Horizons roundtable discussion

With recent prospective clinical trials that used paediatric regimens with multiple doses of pegylated form of asparaginase (PEG asparaginase) in adults reporting significantly improved survival compared with historical data with regimens that used less asparaginase, PEG asparaginase is increasingly being used in the treatment of adult acute lymphoblastic leukaemia (ALL). However, administering asparaginase still comes with its challenges, especially in adult patients. Therefore, it is important to understand how to manage its toxicities properly. An expert group met in November 2019 in London to discuss recent data of paediatric as well as adult studies using paediatric regimens with regard to the best management of several key toxicities that can occur in adults treated with asparaginase including hepatotoxicity, pancreatitis, hypertriglyceridaemia, thrombosis and hypersensitivity. Several recommendations were made for each one of these toxicities, with the goal of safe administration of the drug and to educate clinicians when the drug can be continued despite side effects.

[ALL in adult patients: Contribution and limits of pediatric management]

For two decades, the prognostic of adult patients with ALL was improved based on pediatric-inspired protocols. These approaches based on less myelosuppressive drugs have led to improved response rates, decreased relapse rates, with a benefit in survival observed in patients aged up to 50-60-years-old. Therapeutic intensification came with a decrease in the use of allogeneic hematopoietic stem cell transplantation, with current indications mainly based on the level of measurable residual disease. Pediatric approaches are however limited in older patients or in patients with comorbidities, who are at greater risk to develop adverse effects especially to asparaginase. Future progresses will arise from personalized medicine including targeted therapy in some ALL oncogenic subgroups and immunotherapy. Monoclonal antibodies, bispecific antibodies, antibody drug conjugates and CAR-T cells have shown encouraging results in relapsed/refractory diseases. These strategies are now evaluated frontline in children and adults to further increase the quality of response, to limit the toxicity of treatments including allogeneic transplant. The objective of this review is to discuss the benefit and the limits of pediatric therapeutic strategies in adults and the perspectives offered by new approaches including immunotherapies.

Who Should Receive an Allogeneic Transplant in First Complete Remission?

The decision to incorporate allogeneic hematopoietic stem cell transplant (allo-HSCT) into front-line therapy in adult acute lymphoblastic leukemia (ALL) should be primarily guided by measurable residual disease (MRD) status and the ALL regimen utilized. While there is no doubt that allo-HSCT benefits patients with poor MRD response after induction or consolidation, the indication of allo-HSCT in cases of good MRD clearance is not clear. As targeted immunotherapies result in high MRD-negative CR rates, early incorporation of these therapies may also prove valuable in reducing the need for HCT in the front-line setting. This review discusses the data and controversies related to allo-HSCT in the front-line therapy of Philadelphia chromosome-negative and -positive ALL.

Optimal approach to the treatment of young adults with acute lymphoblastic leukemia in 2020

Akin to the introduction of tyrosine kinase inhibitors to Philadelphia chromosome-positive acute lymphoblastic leukemia (ALL), pediatric-based asparaginase-heavy approaches have revolutionized the treatment of young adults with the Philadelphia chromosome-negative subset the past decades. Once again, we are approaching a new era. An era of precision medicine with immunotherapy and other molecularly targeted treatments that offers unique opportunities to customize treatment intensity with or without hematopoietic stem cell transplantation, reduce the burden of toxicities, and combat persistent residual disease. Recently approved agents for refractory/relapsed B-cell precursor ALL include the chimeric antigen receptor-modified T-cells, the anti-CD22 monoclonal antibody-drug conjugate, inotuzumab ozogamicin, and the bispecific anti-CD19 T-cell engager, blinatumomab. These agents are expected to move widely into the frontline setting along with the proteasome inhibitors, bortezomib and carfilzomib, as well as tyrosine kinase inhibitors for Philadelphia-like rearrangements that are especially frequent among young adults. To this add the BH3 mimetics, venetoclax and navitoclax, which are being widely explored in refractory/relapsed as well as frontline settings for B- and T-cell ALL. The promising anti-CD38 monoclonal antibody, daratumumab, is entering the scene of refractory/relapsed T-ALL, whereas the old purine analogue, nelarabine, is being evaluated in a new upfront setting. This review focuses on 2 main questions: How do we optimize frontline as well as salvage ALL treatment of young adults in the 2020s? Not least, how do we address the current burden of serious toxicities unique to young adults?

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.

Role of Allogeneic HCT as Postremission Therapy for Transplant-Eligible Adult Lymphoblastic Leukemia/Lymphoma After Frontline Hyper-CVAD

BACKGROUND

Hyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone alternating with cytarabine and methotrexate (hyper-CVAD) is a commonly used regimen in adults with acute lymphoblastic leukemia (ALL)/lymphoblastic lymphoma (LBL). Adult patients fit for pediatric-inspired protocols have an excellent outcome with chemotherapy alone. However, it is unclear whether patients receiving hyper-CVAD should undergo allogeneic hematopoietic cell transplantation (HCT) as postremission therapy. Our aim was to examine the role of HCT at first complete remission (CR1) in adult ALL/LBL after hyper-CVAD.

PATIENTS AND METHODS

Adult patients with newly diagnosed ALL/LBL receiving frontline hyper-CVAD from 2008 to 2018 were identified and records retrospectively extracted.

RESULTS

A total of 85 patients were identified and included for further analysis. The median (range) age was 23 (14-68) years, and 56 (66%) were male. A total of 24 (28%) had adverse cytogenetics, and 48 (56%) had at least one risk factor. All patients received hyper-CVAD as induction; induction failure was seen in 10 (12%). A total of 38 patients continued the hyper-CVAD course, while the remaining 47 received HCT in CR1. Three-year event-free survival (EFS) and overall survival for the entire cohort were 51.4% and 61.6%, respectively. Median follow-up of alive patients was 39.9 (3.8-123.8) months. At multivariable analysis for EFS, induction failure was associated with worse outcome (hazard ratio [HR], 4.8; 95% confidence interval [CI] 1.7-13.7; P = .003), whereas HCT in CR1 improved outcome (HR, 0.42; 95% CI 0.18-0.97; P = .044). Furthermore, HCT in CR1 was the only prognostic factor for overall survival (HR, 0.3; 95% CI 0.11-0.85; P = .023).

CONCLUSION

HCT at CR1 resulted in a favorable EFS and overall survival in ALL/LBL patients after hyper-CVAD frontline therapy. Given that hyper-CVAD is a widely used protocol for adult patients, further examination of this observation is warranted.

MiR-7 Functions as a Tumor Suppressor by Targeting the Oncogenes TAL1 in T-Cell Acute Lymphoblastic Leukemia

BACKGROUND

T-cell acute lymphoblastic leukemia is a hematologic malignancy characterized by T-cell proliferation, and in many cases, the ectopic expression of the oncogenic transcription factor T-cell acute lymphocytic leukemia protein 1 (TAL1). MicroRNA-7 has been shown to play a critical role in proliferation, migration, and treatment sensitivity in a diverse array of cancers. In this study, we sought to establish a novel link between microRNA-7 and T-cell acute lymphoblastic leukemia oncogenesis.

MATERIAL AND METHOD

To do so, we characterized gene expression of microRNA-7 as well as TAL1 in both T-cell acute lymphoblastic leukemia patient-derived tissue and cell lines, as well as performing functional luciferase assays to assess microRNA-7 binding to the TAL1 3'-untranslated region. We also performed growth, apoptosis, and migration experiments using 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide, Annexin V, and transwell assays in the context of microRNA-7 overexpression.

RESULTS

We found that microRNA-7 expression is attenuated and inversely correlated with TAL1 expression in TAL1 + T-cell acute lymphoblastic leukemia cells. Additionally, microRNA-7 directly targets and suppresses TAL1 levels. Finally, microRNA-7 overexpression reduces growth, motility, and migration while inducing apoptosis in T-cell acute lymphoblastic leukemia cells, phenotypes that can be rescued by concomitant overexpression of TAL1.

CONCLUSIONS

These results indicate that microRNA-7 functions as a potent tumor suppressor by inhibiting the oncogene TAL1 and suggest microRNA-7 could function as a prognostic biomarker and possible therapeutic in the clinical management of T-cell acute lymphoblastic leukemia.

Curative outcomes following blinatumomab in adults with minimal residual disease B-cell precursor acute lymphoblastic leukemia

Minimal residual disease (MRD) is the strongest predictor of relapse in B-cell precursor acute lymphoblastic leukemia (BCP-ALL). In BLAST study (NCT01207388), adults with BCP-ALL in remission with MRD after chemotherapy received blinatumomab, a CD19 BiTE^® immuno-oncotherapy, 15 µg/m²/day for up to four 6-week cycles (4 weeks continuous infusion, 2 weeks off). Survival was evaluated for 110 patients, including 74 who received HSCT in continuous complete remission. With a median follow-up of 59·8 months, median survival (months) was 36·5 (95% CI: 22.0-not reached [NR]). Median survival was NR (29.5-NR) for complete MRD responders (n = 84) and 14.4 (3.8-32.3) for MRD non-responders (n = 23; p = 0.002); after blinatumomab and HSCT, median survival was NR (25.7-NR) (n = 61) and 16.5 (1.1-NR) (n = 10; p = 0.065), respectively. This final analysis suggests complete MRD response during blinatumomab treatment is curative. Post-hoc analysis of study data suggests while post blinatumomab HSCT may be beneficial in appropriate patients, long-term survival without HSCT is also possible.

Monitoring MRD in ALL: Methodologies, technical aspects and optimal time points for measurement

The accurate determination of minimal or measurable residual disease (MRD) during the early months of therapy in acute lymphoblastic leukemia is well established as the most important independent prognostic biomarker, predicting response to combination chemotherapy. Stratification based on MRD maximizes treatment effectiveness while minimizing adverse effects. Allele-specific real-time quantitative PCR of clone-defining immunoglobin/T-cell receptor gene rearrangements in the patients' leukemic clones and/or multiparametric flow cytometric tracking of leukemia-associated immunophenotypes are considered standard of care. Following recent advances in high throughput sequencing (HTS; next generation sequencing), much attention has been devoted to the development of HTS-based MRD assays, which can increase sensitivity; theoretically only limited by the number of cells input into the assay. Knowledge of the methods and limitations of each technology, along with awareness of the sensitivity and specificity of MRD at particular treatment time points is important in interpretation of the MRD value. MRD negativity at pre-established protocol-appropriate time points guides continuance with consolidation/maintenance chemotherapy, whereas positivity leads to a change to a biological therapy such as blinatumomab and intensification of therapy to allogeneic stem cell transplant. Positivity after maintenance may herald impending relapse enabling treatment intervention. MRD has been integral to the introduction of novel agents and cellular therapies into clinical trials and standard of care, but the long-term predictive value of MRD on outcome of novel therapies is not yet established. Integration of somatic genetics with MRD may further improve accurate identification of patients with the lowest and highest risk of relapse.

Measurable residual disease after the first consolidation predicts the outcomes of patients with acute promyelocytic leukemia treated with all-trans retinoic acid and chemotherapy

We stratified patients with newly diagnosed acute promyelocytic leukemia (APL) according to a white blood cell (WBC) count of ≥ 3 × 10⁹/L (high risk) or < 3 × 10⁹/L (low risk) before administering risk-adapted chemotherapy in combination with all-trans retinoic acid (ATRA). In total, 27 low-risk and 23 high-risk patients were assigned to receive induction and three courses of consolidation with ATRA and anthracycline, followed by 2-year maintenance regimen. High-risk group additionally received cytarabine during 1st consolidation and another one-shot idarubicin treatment during 3rd consolidation. We prospectively monitored measurable residual disease (MRD) after induction and each consolidation. In the low-risk and high-risk groups, 5-year disease-free survival (DFS) rates were 86.5% and 81.2% (p = 0.862), and 5-year overall survival rates were 100% and 84.8% (p = 0.062), respectively. In the MRD-negative and MRD-positive groups, 5-year DFS rates were 91.7% and 78.4% (p = 0.402) and 84.7% and 60.0% (p = 0.102) after induction and 1st consolidation, respectively. Relapse rates were 8.3% and 13.3% (p = 0.570) and 9.0% and 40.0% (p = 0.076) after induction and 1st consolidation, respectively. Achieving MRD-negativity after 1st consolidation, rather than after induction, was a potential predictor of relapse and DFS in patients with APL treated with ATRA + chemotherapy.

Evolving therapy of adult acute lymphoblastic leukemia: state-of-the-art treatment and future directions

Recent years have witnessed major advances that have improved outcome of adults with acute lymphoblastic leukemia (ALL). The emergence of the concept of measurable residual disease has fine-tuned our prognostic models and guided our treatment decisions. The treatment paradigms of ALL have been revolutionized with the advent of tyrosine kinase inhibitors targeting BCR-ABL1, monoclonal antibodies targeting CD20 (rituximab), antibody-drug conjugates targeting CD22 (inotuzumab ozogamicin), bispecific antibodies (blinatumomab), and CD19 chimeric antigen receptor T cell therapy (tisagenlecleucel). These highly effective new agents are allowing for novel approaches that reduce reliance on intensive cytotoxic chemotherapy and hematopoietic stem cell transplantation in first remission. This comprehensive review will focus on the recent advances and future directions in novel therapeutic strategies in adult ALL.

A review of current induction strategies and emerging prognostic factors in the management of children and adolescents with acute lymphoblastic leukemia

INTRODUCTION

Acute lymphoblastic leukemia is the most frequent hematologic malignancy in children. Almost 95% of children potentially achieve a complete remission after the induction treatment, but over the last years, new insights in the genomic disease profile and in minimal residual disease detection techniques have led to an improvement in the prognostic stratification, identifying selected patients' subgroups with peculiar therapeutic needs.

AREAS COVERED

According to a comprehensive search of peer-review literature performed in Pubmed, in this review we summarize the recent evidences on the induction treatment strategies comprised in the children acute lymphoblastic leukemia scenario, focusing on the role of key drugs such as corticosteroids and asparaginase and discussing the crucial significance of the genomic characterization at baseline which may drive the proper induction treatment choice.

EXPERT OPINION

Current induction strategies already produce durable remissions in a significant proportion of standard-risk children with acute lymphoblastic leukemia. A broader knowledge of the biologic features related to acute lymphoblastic leukemia subtypes with worse prognosis, and an optimization of targeted drugs now available, might lead to the achievement of long-term molecular remissions in this setting.

Biology and Treatment Paradigms in T Cell Acute Lymphoblastic Leukemia in Older Adolescents and Adults

OPINION STATEMENT

T cell acute lymphoblastic leukemia (T-ALL) occurs in approximately 25-30% of adult ALL diagnoses. Historically, B cell ALL (B-ALL) and T-ALL have been treated in the same fashion despite differences in the biology of disease. Outcomes in the adolescent/young adult (AYA) population have improved significantly with the utilization of pediatric-based regimens. In addition, there may now be a role for the addition of nelarabine to frontline treatment in the AYA population. In older adults, choices in which regimen to pursue should account for the potential toxicities associated with pediatric-based regimens. Measurable residual disease (MRD) has taken on increasing prognostic value in T-ALL and may help to identify which patients should receive an allogeneic stem cell transplant. T cell lymphoblastic lymphoma (T-LBL) has traditionally been treated similarly to T-ALL, but additional management questions must be considered. Mediastinal irradiation does not seem to clearly improve outcomes, and there is considerable heterogeneity in the central nervous system (CNS) prophylaxis strategy used in prospective trials. CNS prophylaxis in AYA patients with T-ALL, on the other hand, can be safely achieved with intrathecal chemotherapy alone. Prospective data regarding CNS prophylaxis strategies in older adults are currently not available. Nelarabine-based regimens currently remain the standard in relapsed/refractory T-ALL; however, novel therapies targeting molecular aberrations in T-ALL are actively being investigated.

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.

Pre-transplant MRD negativity predicts favorable outcomes of CAR-T therapy followed by haploidentical HSCT for relapsed/refractory acute lymphoblastic leukemia: a multi-center retrospective study

BACKGROUND

Consolidative allogeneic hematopoietic stem cell transplantation is a controversial option for patients with relapsed/refractory acute lymphoblastic leukemia after chimeric antigen receptor T cell (CAR-T) therapy. We performed a multicenter retrospective study to assess whether patients can benefit from haploidentical hematopoietic stem cell transplantation after CAR-T therapy.

METHODS

A total of 122 patients after CAR-T therapy were enrolled, including 67 patients without subsequent transplantation (non-transplant group) and 55 patients with subsequent haploidentical hematopoietic stem cell transplantation (transplant group). Long-term outcome was assessed, as was its association with baseline patient characteristics.

RESULTS

Compared with the non-transplant group, transplantation recipients had a higher 2-year overall survival (OS; 77.0% versus 36.4%; P < 0.001) and leukemia-free survival (LFS; 65.6% versus 32.8%; P < 0.001). Multivariate analysis showed that minimal residual disease (MRD) positivity at transplantation is an independent factor associated with poor LFS (P = 0.005), OS (P = 0.035), and high cumulative incidence rate of relapse (P = 0.045). Pre-transplant MRD-negative recipients (MRD- group) had a lower cumulative incidence of relapse (17.3%) than those in the non-transplant group (67.2%; P < 0.001) and pre-transplant MRD-positive recipients (MRD+ group) (65.8%; P = 0.006). The cumulative incidence of relapse in MRD+ and non-transplant groups did not differ significantly (P = 0.139). The 2-year LFS in the non-transplant, MRD+, and MRD- groups was 32.8%, 27.6%, and 76.1%, respectively. The MRD- group had a higher LFS than the non-transplantation group (P < 0.001) and MRD+ group (P = 0.007), whereas the LFS in the MRD+ and non-transplant groups did not differ significantly (P = 0.305). The 2-year OS of the MRD- group was higher than that of the non-transplant group (83.3% versus 36.4%; P < 0.001) but did not differ from that of the MRD+ group (83.3% versus 62.7%; P = 0.069). The OS in the non-transplant and MRD+ groups did not differ significantly (P = 0.231).

CONCLUSION

Haploidentical hematopoietic stem cell transplantation with pre-transplant MRD negativity after CAR-T therapy could greatly improve LFS and OS in patients with relapsed/refractory acute lymphoblastic leukemia.

TRIAL REGISTRATION

The study was registered in the Chinese clinical trial registry (ChiCTR1900023957).

Hematopoietic Cell Transplantation for Philadelphia Chromosome Negative Adult Acute Lymphoblastic Leukemia in the Modern Era of Immune Therapy

PURPOSE OF REVIEW

This review will discuss the data and controversies related to HCT in the front-line and relapsed/refractory setting in the context of newly available targeted immunotherapies.

RECENT FINDINGS

Recent studies in adult Ph-negative ALL support the use of measurable residual disease (MRD) response to front-line therapy to guide consolidation. As such, most MRD-negative patients do not require front-line HCT. Blinatumomab benefits patients with B-ALL with MRD+ complete response (CR) and can be used as a bridge to HCT; whether HCT is still required in this setting is an area of ongoing inquiry. Blinatumomab and inotuzumab result in high rates of MRD negative CR in adults with relapsed/refractory ALL and allow more patients with relapsed disease to receive HCT. Chimeric antigen receptor T cell (CAR-T) therapies may serve as a bridge to HCT or as a stand-alone therapy for relapsed/refractory patients; data suggests there may be greater benefit to consolidating CAR-T with HCT in HCT-naïve adults. The decision to incorporate consolidative allogeneic HCT into front-line therapy should be primarily guided by MRD status and the ALL regimen utilized. Targeted immunotherapies result in high MRD-negative CR rates, allowing more adults with relapsed/refractory ALL to be successfully bridged to HCT; early incorporation of these therapies may also prove valuable in reducing the need for HCT in the front-line setting by increasing MRD negative CR rates.

Efficacy and safety of humanized anti-CD19-CAR-T therapy following intensive lymphodepleting chemotherapy for refractory/relapsed B acute lymphoblastic leukaemia

We studied the efficacy and safety of humanized CAR-T therapy following intensive chemotherapy for refractory/relapsed (R/R) acute lymphoblastic leukaemia (B-ALL). Twenty-three patients with R/R B-ALL were pretreated with intensive chemotherapy (fludarabine combined with medium-dose cytarabine) 12 days before CAR-T therapy. Adverse events (AEs), curative effects, infection indicators and cytokine release syndrome (CRS) were monitored. Each of the 23 patients received a dose of 1·0 × 10⁶ cells/kg CAR-T cell infusion on day 0. After 14 days, 19 patients (82·61%) achieved complete response (CR) or CR with incomplete count recovery. No survival benefit was achieved with consolidative haematopoietic stem-cell transplantation (HSCT), with a median follow-up of 14·0 months (range, 1·5-21·0 months). The notable AEs were grade 1-2 CRS in 18 patients, while the other five patients were grade 3 CRS. No patients died of CRS. Only one patient died of respiratory failure due to cytomegalovirus infection 24 days after infusion. The proportion of leukaemic cells in bone marrow on infusion day and the peaks of IL-6, TNF-α and IL-8 levels were correlated with CRS levels. A lower disease burden was achieved by intensive lymphodepleting chemotherapy, and the subsequent CAR-T therapy had a high response and manageable toxicity. Trial registration: The patients were enrolled in a clinical trial of ChiCTR-ONN-16009862, and ChiCTR1800019622.

Management of patients with acute lymphoblastic leukemia in routine clinical practice: Minimal residual disease testing, treatment patterns and clinical outcomes in Belgium, Greece and Switzerland

OBJECTIVES

To describe real-world management and clinical and economic outcomes of patients with B-cell precursor acute lymphoblastic leukemia (ALL) in Belgium, Greece and Switzerland.

METHODS

This descriptive, retrospective medical chart review collected patient-level data in 2018 from adults with ≥1 minimal residual disease (MRD) test during front-line ALL treatment. Data were stratified by MRD status.

RESULTS

Eighty-two patients were included (median age 44 years, 23 % Philadelphia chromosome-positive; MRD-positive: n = 17, MRD-negative: n = 50, MRD result unknown: n = 15). HyperCVAD (32 %) and HOVON (26 %) were the most frequently used front-line treatment protocols; 22 % of patients received stem cell transplantation. Overall, 76 % of ALL patients were hospitalized (mean 1.1 hospitalization/month). Complete hematological response (CRh) occurred in 66/82 patients (80 %). Median relapse-free survival from CRh was 32.7 months (MRD-positive: 11.7 months; MRD-negative: 33.3 months). Median overall survival from diagnosis was 28.9 months (MRD-positive: 15.3 months; MRD-negative: not reached). Most patients (88 %) were MRD tested during induction; testing rates considerably decreased thereafter (39 % during consolidation).

CONCLUSIONS

B-cell precursor ALL represents a clinical burden and impacts healthcare resources; MRD-positive patients have worse prognosis than MRD-negative patients. Efforts should be made to adhere to recommendations for MRD testing in clinical guidelines.

Evaluation and management of measurable residual disease in acute lymphoblastic leukemia

With standard chemotherapy regimens for adults with acute lymphoblastic leukemia, approximately 90% of patients achieve complete remission. However, up to half of patients have persistent minimal/measurable residual disease (MRD) not recognized by routine microscopy, which constitutes the leading determinant of relapse. Many studies in pediatric and adult populations have demonstrated that achievement of MRD negativity after induction chemotherapy or during consolidation is associated with significantly better long-term outcomes, and MRD status constitutes an independently prognostic marker, often superseding other conventional risk factors. Persistence of MRD after intensive chemotherapy is indicative of treatment refractoriness and warrants alternative therapeutic approaches including allogeneic stem cell transplantation, blinatumomab, or investigational therapies such as inotuzumab ozogamicin or chimeric antigen receptor T cells. Furthermore, the incorporation of novel monoclonal antibodies or potent BCR-ABL1 tyrosine kinase inhibitors, such as ponatinib into frontline treatment may have the advantage of achieving higher rates of MRD negativity while minimizing chemotherapy-related toxicities. Many studies are therefore ongoing to determine whether this strategy can improve cure rates without the need for allogeneic stem cell transplantation.

Hematopoietic stem cell transplantation for blood cancers in the era of precision medicine and immunotherapy

Hematopoietic stem cell transplantation (HCT) has been an integral component in the treatment of many hematologic malignancies. Since the development of HCT nearly 50 years ago, the role of this modality has evolved as newer treatment approaches have been developed and integrated into the standard of care. In the last decade, novel and highly active targeted therapies and immunotherapies have been approved for many hematologic malignancies, raising the question of whether HCT continues to retain its prominent role in the treatment paradigms of various hematologic malignancies. In this review, the authors have described the current role of autologous and allogeneic HCT in the treatment of patients with acute leukemias, aggressive B-cell lymphomas, and multiple myeloma and discussed how novel targeted therapies and immunotherapies have changed the potential need, timing, and goal of HCT in patients with these diseases.

Practical guidance for the management of acute lymphoblastic leukemia in the adolescent and young adult population

The outstanding therapeutic progress achieved with modern pediatric regimens in childhood acute lymphoblastic leukemia (ALL) led efforts to explore whether a similar treatment approach could be equally effective and safe in older patients, starting initially with older adolescents and young adults (AYA), variably defined in different studies by an age between 15–18 and 25–39 years. Several comparative and noncomparative trials of this type have been carried out during the last two decades, enrolling thousands of patients. Almost without exception, the new strategy improved patients’ outcomes compared with traditional adult treatments in B-lineage and T-lineage Philadelphia (Ph) chromosome-negative B-ALL, while the use of tyrosine kinase inhibitors (TKI) led to comparative progress in Ph+ ALL, a former high-risk subset more typically observed in older age groups. At present, highly effective pediatric-based regimens warrant 5-year survival rates of 60–70% in AYA patients. In view of these data, the same approach was progressively extended to older patients, improving the results up to 55 years of age. Issues of treatment compliance and drug-related toxicity have thus far prevented a comparable therapeutic advancement in patients aged >55 years. This critical review updates and summarizes with pertinent examples this global, positive therapeutic change, and examines how to promote further progress with new targeted therapies that include novel immuno-therapeutics and other agents developed against the many molecular dysfunctions detectable in various ALL subsets. Substantial progress is expected to occur soon, bringing AYA survival figures very close to that of children, and also to improve the outcome of ALL at all ages.

The early achievement of measurable residual disease negativity in the treatment of adults with Philadelphia-negative B-cell acute lymphoblastic leukemia is a strong predictor for survival

The minimal or measurable residual disease (MRD) status following induction/consolidation chemotherapy is an important prognostic endpoint in adult patients with newly diagnosed acute lymphoblastic leukemia (ALL). However, the optimal time-point (TP) of MRD assessment and its impact on outcome remains unclear. We analyzed 215 patients with newly diagnosed Philadelphia negative B-cell ALL who received intensive chemotherapy, and had available MRD assessment by multicolor flow cytometry at two separate TPs. The median time to first TP (1TP) and second TP (2TP) were 24 and 110 days, respectively. At 1TP, 148 patients (68%) were MRD negative and 67 (32%) were positive. Of the 148 patients with negative MRD at 1TP, 147 (99%) maintained it through 2TP. Patients who were MRD negative at both TPs, early MRD responders, had the 3-year event-free survival (EFS), and overall survival (OS) rates of 65% and 76%, respectively. Patients with improved MRD status from positive to negative, late MRD responders, had lower 3-year EFS and OS rates, 42% and 58%, respectively (P = .001). Multivariate analysis showed that KMT2A (MLL) rearrangement and MRD positivity at 1TP were the only factors correlated with worse OS. In conclusion, the earlier achievement of MRD negative remission is a stronger prognostic factor for survival.

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.