Impact of pretransplant minimal residual disease after cord blood transplantation for childhood acute lymphoblastic leukemia in remission: an Eurocord, PDWP–EBMT analysis

Engineering the best transplant outcome for high-risk acute myeloid leukemia: the donor, the graft and beyond

Allogeneic hemopoietic cell transplantation remains the goal of therapy for high-risk acute myeloid leukemia (AML). However, treatment failure in the form of leukemia relapse or severe graft-versus-host disease remains a critical area of unmet need. Recently, significant progress has been made in the cell therapy-based interventions both before and after transplant. In this review, the Stem Cell Engineering Committee of the International Society for Cell and Gene Therapy summarizes the literature regarding the identification of high risk in AML, treatment approaches before transplant, optimal transplant platforms and measures that may be taken after transplant to ideally prevent, or, if need be, treat AML relapse. Although some strategies remain in the early phases of clinical investigation, they are built on progress in pre-clinical research and cellular engineering techniques that are already improving outcomes for children and adults with high-risk malignancies.

A predictive model combining clinical characteristics and nutritional risk factors for overall survival after umbilical cord blood transplantation

BACKGROUND

Umbilical cord blood transplantation (UCBT) is a curable therapy for hematological disease; however, the impact of nutritional status on UCBT outcomes remains controversial. To evaluate the joint effect of clinical characteristics and nutritional status on the prognosis of patients who underwent UCBT, we screened various factors to establish a predictive model of overall survival (OS) after UCBT.

METHODS

We performed an integrated clinical characteristic and nutritional risk factor analysis and established a predictive model that could be used to identify UCBT recipients with poor OS. Internal validation was performed by using the bootstrap method with 500 repetitions.

RESULTS

Four factors, including disease status, conditioning regimen, calf skinfold thickness and albumin level, were identified and used to develop a risk score for OS, which showed a positive predictive value of 84.0%. A high-risk score (≥ 2.225) was associated with inferior 3-year OS post-UCBT [67.5% (95% CI 51.1-79.4%), P = 0.001]. Then, we built a nomogram based on the four factors that showed good discrimination with a C-index of 0.833 (95% CI 0.743-0.922). The optimism-corrected C-index value of the bootstrapping was 0.804. Multivariate analysis suggested that a high calf skinfold thickness (≥ 20.5 mm) and a low albumin level (< 33.6 g/L) conferred poor disease-free survival (DFS).

CONCLUSION

The predictive model combining clinical and nutritional factors could be used to predict OS in UCBT recipients, thereby promoting preemptive treatment.

Efficacy and safety of blinatumomab in children with relapsed/refractory B cell acute lymphoblastic leukemia: A systematic review and meta-analysis

Objectives: Several clinical trials have been conducted to evaluate the effects of blinatumomab in childhood B cell acute lymphoblastic leukemia (B-ALL). We conducted this meta-analysis to validate the efficacy and safety of blinatumomab in pediatric patients with relapsed/refractory B-ALL (R/R B-ALL). Methods: We searched and investigated all relevant studies in the PubMed, Web of Science, Embase, and Cochrane Library databases. The primary outcomes were complete response (CR), overall survival (OS), event free survival (EFS), minimal residual disease (MRD) response, allogeneic hematopoietic stem cell transplantation (allo-HSCT) and were calculated separately for randomized controlled trials (RCTs) and single-arm studies. The secondary end points were adverse effects (AEs) and the relapse rate. The Cochrane, bias assessment tool, was used to assess the risk of bias in RCTs. The methodological quality of single-arm studies was assessed using the methodological index for non-randomized studies (MINORS) tool. Results: The meta-analysis included two RCTs and 10 single-arm studies, including 652 patients in total. Our study showed that in the single-arm studies, the combined CR rate was 0.56 (95% confidence interval (CI): 0.45 -0.68), the odds ratios (ORs) of OS was 0.43 (95% CI 0.32 -0.54), the EFS rate was 0.30 (95% CI: 0.20 -0.40), the MRD response was 0.51 (95% CI: 0.34 -0.68), allo-HSCT rate was 0.62 (95% CI: 0.50 -.74), the AE rate was 0.65 (95% CI: 0.54 -0.76) and the relapse rate was 0.32 (95% CI: 0.27 -0.38). In the RCTs, the blinatumomab-treated group compared with the chemotherapy group had a combined OS rate of 0.12 (95% CI: 0.05 -0.19) and an EFS rate of 2.16 (95% CI: 1.54 -3.03). The pooled MRD response rate was 4.71 (95% CI:2.84 -7.81), allo-HSCT was 3.24 (95% CI: 1.96 -5.35), the AE rate was 0.31 (95% CI: 0.16 -0.60), and the relapse rate was 0 .69 (95% CI: 0.43 -1.09). Conclusion: According to this meta-analysis, blinatumomab shows potent therapeutic efficacy and limited AEs in children with R/R B- ALL. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/, identifier CRD42022361914.

Blinatumomab overcomes poor prognostic impact of measurable residual disease in pediatric high-risk first relapse B-cell precursor acute lymphoblastic leukemia

BACKGROUND

Blinatumomab, a CD3/CD19 BiTE^® (bispecific T cell engager) molecule, was superior to high-risk third course consolidation chemotherapy (HC3) in prolonging event-free survival (EFS) in children with high-risk first relapse B-cell precursor acute lymphoblastic leukemia (B-ALL). Here, we report results from a post hoc measurable residual disease (MRD) analysis of this phase 3 study (NCT02393859).

PROCEDURE

Children >28 days and <18 years with high-risk first-relapse B-ALL in cytomorphological complete remission (M1 marrow, <5% blasts) or with M2 marrow (≥5% and <25% blasts) after induction and two cycles of high-risk consolidation chemotherapy (baseline) were enrolled in this trial. Patients received one cycle of blinatumomab (15 μg/m² /day, 4 weeks, continuous intravenous infusion) or HC3. The primary endpoint was EFS. In this post hoc analysis, patients with MRD <10^-4 by PCR were grouped as having positive but not quantifiable (pbnq) or undetectable disease.

RESULTS

A higher proportion of patients with MRD <10^-4 had undetectable versus pbnq disease after blinatumomab (day 29) than after HC3 (p = 0.0367). Of the 22 patients with MRD ≥10^-4 at baseline who achieved MRD remission after blinatumomab, 20 (91%) achieved MRD <10^-4 remission by day 15. Patients treated with blinatumomab had improved EFS and overall survival compared with those treated with HC3 independent of end-of-induction or baseline (end-of-second consolidation) MRD levels.

CONCLUSIONS

Blinatumomab was more efficacious than HC3 regardless of MRD status before treatment. These data support the role of blinatumomab in inducing deep MRD remission, negating the poor prognostic value of MRD.

Blinatumomab in pediatric relapsed/refractory B-cell acute lymphoblastic leukemia: RIALTO expanded access study final analysis

The safety and efficacy of blinatumomab, a CD3/CD19-directed bispecific molecule, were examined in an open-label, single-arm, expanded access study (RIALTO). Children (>28 days and <18 years) with CD19+ relapsed/refractory B-cell precursor acute lymphoblastic leukemia (R/R B-ALL) received up to 5 cycles of blinatumomab by continuous infusion (cycle: 4 weeks on/2 weeks off). The primary end point was incidence of adverse events. Secondary end points included complete response (CR) and measurable residual disease (MRD) response within the first 2 cycles and relapse-free survival (RFS), overall survival (OS), and allogeneic hematopoietic stem cell transplant (alloHSCT) after treatment. At final data cutoff (10 January 2020), 110 patients were enrolled (median age, 8.5 years; 88% had ≥5% baseline blasts). A low incidence of grade 3 or 4 cytokine release syndrome (n = 2; 1.8%) and neurologic events (n = 4; 3.6%) was reported; no blinatumomab-related fatal adverse events were recorded. The probability of response was not affected by the presence of cytogenetic/molecular abnormalities. Median OS was 14.6 months (95% confidence interval [CI]: 11.0-not estimable) and was significantly better for MRD responders vs MRD nonresponders (not estimable vs 9.3; hazard ratio, 0.18; 95% CI: 0.08-0.39). Of patients achieving CR after 2 cycles, 73.5% (95% CI: 61.4%-83.5%) proceeded to alloHSCT. One-year OS probability was higher for patients who received alloHSCT vs without alloHSCT after blinatumomab (87% vs 29%). These findings support the use of blinatumomab as a safe and efficacious treatment of pediatric R/R B-ALL. This trial was registered at www.clinicaltrials.gov as #NCT02187354.

The Role of Allogeneic Hematopoietic Stem Cell Transplantation in Pediatric Leukemia

Allogeneic hematopoietic stem cell transplantation (HSCT) offers potentially curative treatment for many children with high-risk or relapsed acute leukemia (AL), thanks to the combination of intense preparative radio/chemotherapy and the graft-versus-leukemia (GvL) effect. Over the years, progress in high-resolution donor typing, choice of conditioning regimen, graft-versus-host disease (GvHD) prophylaxis and supportive care measures have continuously improved overall transplant outcome, and recent successes using alternative donors have extended the potential application of allotransplantation to most patients. In addition, the importance of minimal residual disease (MRD) before and after transplantation is being increasingly clarified and MRD-directed interventions may be employed to further ameliorate leukemia-free survival after allogeneic HSCT. These advances have occurred in parallel with continuous refinements in chemotherapy protocols and the development of targeted therapies, which may redefine the indications for HSCT in the coming years. This review discusses the role of HSCT in childhood AL by analysing transplant indications in both acute lymphoblastic and acute myeloid leukemia, together with current and most promising strategies to further improve transplant outcome, including optimization of conditioning regimen and MRD-directed interventions.

Effect of Blinatumomab vs Chemotherapy on Event-Free Survival Among Children With High-risk First-Relapse B-Cell Acute Lymphoblastic Leukemia: A Randomized Clinical Trial

IMPORTANCE

Blinatumomab is a CD3/CD19-directed bispecific T-cell engager molecule with efficacy in children with relapsed or refractory B-cell acute lymphoblastic leukemia (B-ALL).

OBJECTIVE

To evaluate event-free survival in children with high-risk first-relapse B-ALL after a third consolidation course with blinatumomab vs consolidation chemotherapy before allogeneic hematopoietic stem cell transplant.

DESIGN, SETTING, AND PARTICIPANTS

In this randomized phase 3 clinical trial, patients were enrolled November 2015 to July 2019 (data cutoff, July 17, 2019). Investigators at 47 centers in 13 countries enrolled children older than 28 days and younger than 18 years with high-risk first-relapse B-ALL in morphologic complete remission (M1 marrow, <5% blasts) or with M2 marrow (blasts ≥5% and <25%) at randomization.

INTERVENTION

Patients were randomized to receive 1 cycle of blinatumomab (n = 54; 15 μg/m2/d for 4 weeks, continuous intravenous infusion) or chemotherapy (n = 54) for the third consolidation.

MAIN OUTCOMES AND MEASURES

The primary end point was event-free survival (events: relapse, death, second malignancy, or failure to achieve complete remission). The key secondary efficacy end point was overall survival. Other secondary end points included minimal residual disease remission and incidence of adverse events.

RESULTS

A total of 108 patients were randomized (median age, 5.0 years [interquartile range {IQR}, 4.0-10.5]; 51.9% girls; 97.2% M1 marrow) and all patients were included in the analysis. Enrollment was terminated early for benefit of blinatumomab in accordance with a prespecified stopping rule. After a median of 22.4 months of follow-up (IQR, 8.1-34.2), the incidence of events in the blinatumomab vs consolidation chemotherapy groups was 31% vs 57% (log-rank P < .001; hazard ratio [HR], 0.33 [95% CI, 0.18-0.61]). Deaths occurred in 8 patients (14.8%) in the blinatumomab group and 16 (29.6%) in the consolidation chemotherapy group. The overall survival HR was 0.43 (95% CI, 0.18-1.01). Minimal residual disease remission was observed in more patients in the blinatumomab vs consolidation chemotherapy group (90% [44/49] vs 54% [26/48]; difference, 35.6% [95% CI, 15.6%-52.5%]). No fatal adverse events were reported. In the blinatumomab vs consolidation chemotherapy group, the incidence of serious adverse events was 24.1% vs 43.1%, respectively, and the incidence of adverse events greater than or equal to grade 3 was 57.4% vs 82.4%. Adverse events leading to treatment discontinuation were reported in 2 patients in the blinatumomab group.

CONCLUSIONS AND RELEVANCE

Among children with high-risk first-relapse B-ALL, treatment with 1 cycle of blinatumomab compared with standard intensive multidrug chemotherapy before allogeneic hematopoietic stem cell transplant resulted in an improved event-free survival at a median of 22.4 months of follow-up.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02393859.

Cord blood transplantation for acute leukemia

INTRODUCTION

Umbilical cord blood transplantation (UCBT) is a suitable alternative for patients with acute leukemia (AL) in need of an allograft and who lack an HLA-matched donor. Single-institution and registry studies have shown that, in both children and adults with AL, the outcome of UCBT is comparable to that of matched unrelated donor. At the same time, these studies have highlighted some limitations of UCBT, such as increased early mortality and delayed recovery of both hematopoietic and immune compartment, which hamper a more widespread adoption of this approach.

AREAS COVERED

In this review, we will analyze the current results of UCBT in children and adults with AL, including comparisons with other hematopoietic stem cell sources and transplant strategies. We will also discuss important factors to be considered when selecting UCB units, as well as future strategies to further improve the outcome of UCBT recipients.

EXPERT OPINION

The utilization of UCBT for the treatment of AL patients has decreased in recent years. However, recent clinical data suggesting that UCBT might offer better results in patients with minimal residual disease, as well as innovative strategies to facilitate engraftment, reduce transplant-related mortality, and optimize anti-leukemic activity, may pave the way toward a second youth for use of UCB cells.

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.

Optimizing cord blood selection

Nowadays a donor can be found for virtually all patients in need of an allogeneic stem cell transplantation, and the decision whether to use a matched or mismatched unrelated donor, an unrelated donor for umbilical cord blood transplantation (UCBT), or a haploidentical donor depends not only on the availability of the donor but also on patient-, disease-, and center-related factors. This paper summarizes the recent criteria in the selection of cord blood unit, including the cell dose requirement and the HLA typing for the optimal donor choice. The main strategies to optimize the results of UCBT, the conditioning regimens, and the use of antithymocyte globulin and the other platforms of graft-versus-host disease prophylaxis are discussed. The paper describes the results of UCBT in children and adults with malignant and nonmalignant diseases and the comparative analysis with other donor type and stem cell sources. Emerging strategies, focusing on the different platforms of ex vivo expansion and the new applications using cord blood stem cell, are also examined.

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.

Advances in hematopoietic cell transplant for the treatment of hematologic malignancies

PURPOSE OF REVIEW

Incorporation of minimal residual disease (MRD) testing in acute lymphoblastic leukemia (ALL) and acute myeloblastic leukemia (AML) has transformed the landscape of hematopoietic cell transplantation (HCT). Pre-HCT MRD has allowed prognostication of HCT outcomes for high-risk leukemia patients, whereas the detection of post-HCT MRD has allowed for interventions to decrease relapse.

RECENT FINDINGS

In this review, we emphasize studies from the past two decades that highlight the critical role of MRD in HCT in pediatric ALL and AML. Advances in MRD detection methodology, using next-generation sequencing, have improved the sensitivity of MRD testing allowing for more accurate predictions of HCT outcomes for patients with relapsed and refractory ALL and AML. In addition, novel pre-HCT therapies, especially immunotherapy in ALL, have dramatically increased the number of patients who achieve MRD-negative remissions pre-HCT, resulting in improved HCT outcomes. Post-HCT MRD remains a challenge and new therapeutic interventions are needed to reduce post-HCT relapse.

SUMMARY

As immunotherapy increases pre-HCT MRD-negative remissions, and next-generation sequencing-MRD is incorporated to improve the sensitivity of MRD detection, future clinical studies will investigate less toxic HCT approaches to reduce long-term sequelae and to identify which patients may benefit most from early post-HCT intervention to reduce relapse.

Methods and role of minimal residual disease after stem cell transplantation

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

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

BACKGROUND

This meta-analysis was performed to explore the impact of minimal residual disease (MRD) prior to transplantation on the prognosis for patients with acute lymphoblastic leukemia (ALL).

METHODS

A systematic search of PubMed, Embase, and the Cochrane Library was conducted for relevant studies from database inception to March 2016. A total of 21 studies were included.

RESULTS

Patients with positive MRD prior to allogeneic stem cell transplantation (allo-SCT) had a significantly higher rate of relapse compared with those with negative MRD (HR = 3.26; P <  0.05). Pre-transplantation positive MRD was a significant negative predictor of relapse-free survival (RFS) (HR = 2.53; P <  0.05), event-free survival (EFS) (HR = 4.77; P < 0.05), and overall survival (OS) (HR = 1.98; P < 0.05). However, positive MRD prior to transplantation was not associated with a higher rate of nonrelapse mortality.

CONCLUSIONS

Positive MRD before allo-SCT was a predictor of poor prognosis after transplantation in ALL.

TRIAL REGISTRATION

Not applicable.

Factors Associated with Long-Term Risk of Relapse after Unrelated Cord Blood Transplantation in Children with Acute Lymphoblastic Leukemia in Remission

For pediatric patients with acute lymphoblastic leukemia (ALL), relapse is an important cause of treatment failure after unrelated cord blood transplant (UCBT). Compared with other donor sources, relapse is similar or even reduced after UCBT despite less graft-versus-host disease (GVHD). We performed a retrospective analysis to identify risk factors associated with the 5-year cumulative incidence of relapse after UCBT. In this retrospective, registry-based study, we examined the outcomes of 640 children (<18 years) with ALL in first complete remission (CR1; n = 257, 40%) or second complete remission (CR2; n = 383, 60%) who received myeloablative conditioning followed by a single-unit UCBT from 2000 to 2012. Most received antithymocyte globulin (88%) or total body irradiation (TBI; 69%), and cord blood grafts were primarily mismatched at 1 (50%) or 2+ (34%) HLA loci. Considering patients in CR1, the rates of 5-year overall survival (OS), leukemia-free survival (LFS), and relapse were 59%, 52%, and 23%, respectively. In multivariate analysis (MVA), acute GVHD (grades II to IV) and TBI protected against relapse. In patients in CR2, rates of 5-year OS, LFS, and the cumulative incidence of relapse were 46%, 44%, and 28%, respectively. In MVA, longer duration from diagnosis to UCBT (≥30 months) and TBI were associated with decreased relapse risk. Importantly, receiving a fully HLA matched graft was a strong risk factor for increased relapse in MVA. An exploratory analysis of all 640 patients supported the important association between the presence of acute GVHD and less relapse but also demonstrated an increased risk of nonrelapse mortality. In conclusion, the impact of GVHD as a graft-versus-leukemia marker is evident in pediatric ALL after UCBT. Strategies that promote graft-versus-leukemia while harnessing GVHD should be further investigated.

When Less Is Good, Is None Better? The Prognostic and Therapeutic Significance of Peri-Transplant Minimal Residual Disease Assessment in Pediatric Acute Lymphoblastic Leukemia

The measurement of minimal residual disease (MRD) in pediatric acute lymphoblastic leukemia (ALL) has become the most important prognostic tool of, and the backbone to, upfront risk stratification. While MRD assessment is the standard of care for assessing response and predicting outcomes for pediatric patients with ALL receiving chemotherapy, its use in allogeneic hematopoietic stem cell transplant (HSCT) has been less clearly defined. Herein, we discuss the importance of MRD assessment during the peri-HSCT period and its role in prognostication and management.

Nonmyeloablative Haploidentical Bone Marrow Transplantation with Post-Transplantation Cyclophosphamide for Pediatric and Young Adult Patients with High-Risk Hematologic Malignancies

Lower-intensity conditioning regimens for haploidentical blood or marrow transplantation (BMT) are safe and efficacious for adult patients with hematologic malignancies. We report data for pediatric/young adult patients with high-risk hematologic malignancies (n = 40) treated with nonmyeloablative haploidentical BMT with post-transplantation cyclophosphamide from 2003 to 2015. Patients received a preparative regimen of fludarabine, cyclophosphamide, and total body irradiation. Post-transplantation immunosuppression consisted of cyclophosphamide, mycophenolate mofetil, and tacrolimus. Donor engraftment occurred in 29 of 32 (91%), with median time to engraftment of neutrophils >500/µL of 16 days (range, 13 to 22) and for platelets >20,000/µL without transfusion of 18 days (range, 12 to 62). Cumulative incidences of acute graft-versus-host disease (GVHD) grades II to IV and grades III and IV at day 100 were 33% and 5%, respectively. The cumulative incidence of chronic GVHD was 23%, with 7% moderate-to-severe chronic GVHD, according to National Institutes of Health consensus criteria. Transplantation-related mortality (TRM) at 1 year was 13%. The cumulative incidence of relapse at 2 years was 52%. With a median follow-up of 20 months (range, 3 to 148), 1-year actuarial overall and event-free survival were 56% and 43%, respectively. Thus, we demonstrate excellent rates of engraftment, GVHD, and TRM in pediatric/young adult patients treated with this regimen. This approach is a widely available, safe, and feasible option for pediatric and young adult patients with high-risk hematologic malignancies, including those with a prior history of myeloablative BMT and/or those with comorbidities or organ dysfunction that preclude eligibility for myeloablative BMT.

The impact of minimal residual disease prior to unmanipulated haploidentical hematopoietic stem cell transplantation in patients with acute myeloid leukemia in complete remission

The minimal residual disease (MRD) before and after a haploidentical hematopoietic stem cell transplantation (HSCT) of 86 patients with acute myeloid leukemia (AML) in complete remission (CR) was measured using flow cytometry (FCM) and Wilms tumor 1 (WT1). In all, 18 patients met the criteria of pre-MRD + before HSCT. The FCM + (p = .028) and the combinative criteria for positive MRD (MRDco+) (p = .022) post-transplantation were significantly correlated to relapse in univariate analysis. A multivariate analysis showed that only MRDco + post-transplantation was an independent risk factor of leukemia relapse (p = .022, HR = 4.653, 95% CI: 1.249-17.334). A significant difference in the cumulative incidence of relapse between patients with or without post-transplant MRDco + was observed (p < .001). However, the results suggested that the MRD status before transplantation might not affect leukemia relapse of patients with AML in CR after haploidentical HSCT. These types of patients might not need to receive further intensive chemotherapy or active intervention concerning HSCT.

Improvement of the Outcome of Relapsed or Refractory Acute Lymphoblastic Leukemia in Children Using a Risk-Based Treatment Strategy

Relapsed/refractory acute lymphoblastic leukemia (ALL) is a leading cause of death by cancer in children. Our institution has switched relapse treatment strategy to improve survival. We reviewed records of first relapse/refractory childhood ALL between 1996 and 2012. Based on length of first remission, relapse site and immunophenotype, patients were classified into two groups: standard-risk relapse (SRR) and high-risk relapse and refractory (HRRR). Before 2007, all patients were uniformly treated with the same induction as at presentation, followed by hematopoietic stem cell transplantation (HSCT). Since 2007, treatment was given according to risk of failure: SRR were mostly treated with chemotherapy; HRRR patients underwent HSCT after intensive chemotherapy, aiming reduction of pre-transplant disease burden. Sixty-four patients were included. Thirty (47%) were SRR and 34 (53%) HRRR, including 11 with refractory ALL. Five-years overall survival (OS) and event-free survival (EFS) were similar for SRR, but were significantly higher with new risk-based strategy for HRRR: 56% versus 17% (P = 0.03) for OS, and 56% vs 11% for EFS (P = 0.008), respectively. In multivariate analysis, treatment strategy was significantly associated with survival. In conclusion, change for a risk-based strategy in our institution increased survival of high-risk patients to levels similar of those of standard-risk patients.

Cord-Blood Transplantation in Patients with Minimal Residual Disease

BACKGROUND

The majority of patients in need of a hematopoietic-cell transplant do not have a matched related donor. Data are needed to inform the choice among various alternative donor-cell sources.

METHODS

In this retrospective analysis, we compared outcomes in 582 consecutive patients with acute leukemia or the myelodysplastic syndrome who received a first myeloablative hematopoietic-cell transplant from an unrelated cord-blood donor (140 patients), an HLA-matched unrelated donor (344), or an HLA-mismatched unrelated donor (98).

RESULTS

The relative risks of death and relapse between the cord-blood group and the two other unrelated-donor groups appeared to vary according to the presence of minimal residual disease status before transplantation. Among patients with minimal residual disease, the risk of death was higher in the HLA-mismatched group than in the cord-blood group (hazard ratio, 2.92; 95% confidence interval [CI], 1.52 to 5.63; P=0.001); the risk was also higher in the HLA-matched group than in the cord-blood group but not significantly so (hazard ratio, 1.69; 95% CI, 0.94 to 3.02; P=0.08). Among patients without minimal residual disease, the hazard ratios were lower (hazard ratio in the HLA-mismatched group, 1.36; 95% CI, 0.76 to 2.46; P=0.30; hazard ratio in the HLA-matched group, 0.78; 95% CI, 0.48 to 1.28; P=0.33). The risk of relapse among patients with minimal residual disease was significantly higher in the two unrelated-donor groups than in the cord-blood group (hazard ratio in the HLA-mismatched group, 3.01; 95% CI, 1.22 to 7.38; P=0.02; hazard ratio in the HLA-matched group, 2.92; 95% CI, 1.34 to 6.35; P=0.007). Among patients without minimal residual disease, the magnitude of these associations was lower (hazard ratio in the HLA-mismatched group, 1.28; 95% CI, 0.51 to 3.25; P=0.60; hazard ratio in the HLA-matched group, 1.30; 95% CI, 0.65 to 2.58; P=0.46).

CONCLUSIONS

Our data suggest that among patients with pretransplantation minimal residual disease, the probability of overall survival after receipt of a transplant from a cord-blood donor was at least as favorable as that after receipt of a transplant from an HLA-matched unrelated donor and was significantly higher than the probability after receipt of a transplant from an HLA-mismatched unrelated donor. Furthermore, the probability of relapse was lower in the cord-blood group than in either of the other groups.

Umbilical cord blood cells from unrelated donor as an alternative source of hematopoietic stem cells for transplantation in children and adults

Umbilical cord blood (CB) is an alternative source of hematopoietic stem cells (HSC) for patients requiring allogeneic HSC transplantation but lacking a suitable human leukocyte antigen (HLA)-matched donor. Using CB has many advantages, including lower HLA-matching requirements, increased donor availability, and low rates of graft-versus-host disease. Furthermore, with over 630,000 cryopreserved volunteer CB units currently stored in international CB banks worldwide, CB is rapidly available for those patients requiring urgent transplantation. However, concern remains over the low HSC doses available in CB grafts, resulting in delayed engraftment and poor immune reconstitution. This article reviews the current use and future developments of unrelated allogeneic CB transplantation (CBT). An overview of the encouraging results of CBT and the comparisons with other HSC sources and transplant strategies both in children and adults with malignant and non-malignant diseases are shown. We will discuss important factors that need to be considered when selecting CB units for transplantation to further improve the results of CBT.

Impact of pretransplant minimal residual disease on the post-transplant outcome of pediatric acute lymphoblastic leukemia

There are few reports on the clinical significance of MRD before HSCT in pediatric ALL. We retrospectively analyzed the clinical significance of FCM-based detection of MRD (FCM-MRD) before allogeneic HSCT in pediatric ALL. Of 38 pediatric patients who underwent allogeneic HSCT for the first time between 1998 and 2014, 33 patients were in CR and five patients were in non-CR. The CR group was further divided into two groups based on the pretransplant FCM-MRD level: the MRD(neg) (<0.01%; 30 patients) group and the MRD(pos) (≥0.01%; three patients) group. There were significant differences in the three-yr event-free survival rates between the CR and non-CR group, and between the MRD(neg) and MRD(pos) group. The three-yr cumulative RI in the MRD(neg) group were 27.3% ± 8.8%, whereas two of the three patients in the MRD(pos) group relapsed within one yr after HSCT. The clinical outcome of the MRD(pos) group was as poor as that of the non-CR group in pediatric ALL. Therefore, an improvement in pretransplant treatment that aims to achieve a more profound remission would contribute to reducing the risk of relapse.

Alternative donors: cord blood for adults

Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative treatment for patients with hematological diseases. The probability of finding a human leukocyte antigen (HLA)- identical donor among family members is around 25% and 30% that of having a full matched unrelated donor in the registry. Patients in need may also benefit of a HLA-mismatched HSCT either from an haploidentical donors or from umbilical cord blood (UCB). Much has been learned about UCB transplant (UCBT) since the first human UCBT was performed back in 1988. Cord blood banks have been established worldwide for the collection, cryopreservation, and distribution of UCB for HSCT. Today, a global network of cord blood banks and transplant centers has been established with a large common inventory of more than 650,000 UCB units available, allowing for more than 40,000 UCBT worldwide in children and adults with severe hematological diseases. Several studies have been published on UCBT, assessing risk factors such as cell dose and HLA mismatch. Outcomes of several retrospective comparative studies showed similar results using other stem cell sources both in pediatric and adult setting. New strategies are ongoing to facilitate engraftment and reduce transplant-related mortality. In this issue, we review the current results of UCBT in adults with hematological malignancies and the clinical studies comparing UCBT with other transplant strategies. We provide guidelines for donor algorithm selection in UCBT setting.

Refractory acute lymphoblastic leukemia in Chinese children: bridging to stem cell transplantation with clofarabine, cyclophosphamide and etoposide

Refractory or relapsed acute lymphoblastic leukemia (r/r ALL) represents the leading cause of cancer mortality in children. Clofarabine is effective in inducing remission thus enabling bridging to hematopoietic stem cell transplantation (HSCT). We report the results in treating Hong Kong Chinese pediatric patients with r/rALL by clofarabine/cyclophosphamide/etoposide (CLO-218) combination therapy. A retrospective review of patients treated between January 2009 and December 2014 in the two tertiary referral pediatric oncology units in Hong Kong. Thirteen patients were identified. All were Chinese and seven were male. Median age at clofarabine treatment was 8 years and the median duration of follow-up was 10 months. Nine patients had B-ALL and four had T-ALL. All were refractory to the preceding regimen(s). The median number of prior treatment regimens was 2; two patients had previous HSCT. Complete remission (CR) was achieved in five patients, Complete remission with incomplete counts (CRi) in two, PR in two, and non-remission (NR) in two. All four patients with T-ALL responded with three patients achieving CR. Eight out of nine patients who responded could be bridged to HSCT. Among those who were transplanted, four remained alive and in remission, three relapsed post-HSCT, and one died from transplant-related mortality. Treatment toxicities were common including febrile neutropenia in all subjects and culture-proven bacteremia in five patients. Hepatotoxicity was mild and reversible with no case of veno-occlusive disease. The clofarabine-based regimen is a promising strategy to induce disease remission in r/rALL and bridge to HSCT. Septic complications are, however, frequent necessitating prompt management with adequate supportive care in specialized centers.

Impact of minimal residual disease on outcomes after umbilical cord blood transplantation for adults with Philadelphia-positive acute lymphoblastic leukaemia: an analysis on behalf of Eurocord, Cord Blood Committee and the Acute Leukaemia working party of the European group for Blood and Marrow Transplantation

The status of umbilical cord blood transplantation (UCBT) in adults with Philadelphia-positive acute lymphoblastic leukaemia (Ph+ALL) and the impact of minimal residual disease (MRD) before transplant are not well established. We analysed 98 patients receiving UCBT for Ph+ALL in first (CR1) or second (CR2) complete remission (CR1, n = 79; CR2, n = 19) with MRD available before UCBT (92% analysed by reverse transcription polymerase chain reaction). Median age was 38 years and median follow-up was 36 months; 63% of patients received myeloablative conditioning and 42% received double-unit UCBT. Eighty-three patients were treated with at least one tyrosine kinase inhibitor before UCBT. MRD was negative (-) in 39 and positive (+) in 59 patients. Three-year cumulative incidence of relapse was 34%; 45% in MRD+ and 16% in MRD- patients (P =0·013). Three-year cumulative incidence of non-relapse mortality was 31%; it was increased in patients older than 35 years (P = 0·02). Leukaemia-free survival (LFS) at 3 years was 36%; 27% in MRD+ and 49% in MRD- patients (P = 0·05), and 41% for CR1 and 14% for CR2 (P = 0·008). Multivariate analysis identified only CR1 as being associated with improved LFS. In conclusion, MRD+ before UCBT is associated with increased relapse. Strategies to decrease relapse in UCBT recipients with Ph+ALL and MRD+ are needed.

Minimal residual disease before and after transplantation for childhood acute lymphoblastic leukaemia: is there any room for intervention?

Eighty-two children and adolescents who underwent allogeneic transplantation for acute lymphoblastic leukaemia in remission (period 2001-2011, median follow-up 4·9 years) had been assessed for minimal residual disease (MRD) by real-time quantitative polymerase chain reaction before and at 1, 3, 6, 9 and 12 months after transplantation. Five-year event-free survival (EFS) and cumulative incidence of relapse were 77·7% [standard error (SE) 5·7] and 11·4% (SE 4·4), respectively, for patients with pre-transplant MRD <1 × 10(-4) (68%), versus 30·8% (SE 9·1; P < 0·001) and 61·5% (SE 9·5; P < 0·001), respectively, for those with MRD ≥1 × 10(-4) (32%). Pre-transplant MRD ≥1 × 10(-4) was associated with a 9·2-fold risk of relapse [95% confidence interval (CI) 3·54-23·88; P < 0·001] compared with patients with MRD <1 × 10(-4). Patients who received additional chemotherapy pre-transplant to reduce MRD had a fivefold reduction of risk of failure (hazard ratio 0·19, CI 0·05-0·70, P = 0·01). Patients who experienced MRD positivity post-transplant did not necessarily relapse (5-year EFS 40·3%, SE 9·3), but had a 2·5-fold risk of failure (CI 1·05-5·75; P = 0·04) if any MRD was detected in the first 100 d, which increased to 7·8-fold (CI 2·2-27·78; P = 0·002) if detected after 6 months. Anticipated immunosuppression-tapering according to MRD may have improved outcome, nevertheless all patients with post-transplant MRD ≥1 × 10(-3) ultimately relapsed, regardless of immunosuppression discontinuation or donor-lymphocyte-infusion. In conclusion, MRD before transplantation had the strongest impact on relapse and MRD positivity after transplantation, mostly if detected early and at low levels, did not necessarily imply relapse. Additional intensified chemotherapy and modulation of immunosuppression may reduce relapse risk and improve ultimate outcome.

Transplantation of CD3/CD19 depleted allografts from haploidentical family donors in paediatric leukaemia

Transplantation of T- and B-cell depleted allografts from haploidentical family donors was evaluated within a prospective phase II trial in children with acute lymphoblastic leukaemia, acute myeloid leukaemia and advanced myelodysplastic syndrome (n = 46). 20 patients had active disease; 19 patients received a second or third stem cell transplantation (SCT). Toxicity-reduced conditioning regimens consisted of fludarabine or clofarabine (in active disease only), thiotepa, melphalan and serotherapy. Graft manipulation was carried out with immunomagnetic microbeads. Primary engraftment occurred in 88%, with a median time to reach >1·0 × 10⁹/l leucocytes, >20 × 10⁹/l platelets and >0·1 × 10⁹/l T-cells of 10, 11 and 50 days, respectively. After retransplantation, engraftment occurred in 100%. Acute graft-versus-host disease (GvHD) grade II and III-IV occurred in 20% and 7%, chronic GvHD occurred in 21%. Both conditioning regimens had comparable toxicity. Transplant-related mortality (TRM) was 8% at one year and 20% at 5 years. Event-free survival at 3 years was: 25% (whole group), 46% (first, second or third complete remission [CR], first SCT) vs. 8% (active disease, first SCT) and 20% (second or third SCT, any disease status). This approach allows first or subsequent haploidentical SCTs to be performed with low TRM. Patients in CR may benefit from SCT, whereas the results in patients with active disease were poor.

A clofarabine-based bridging regimen in patients with relapsed ALL and persistent minimal residual disease (MRD)

In patients with relapsed ALL, minimal residual disease (MRD) identified prior to allogeneic hematopoietic cell transplantation (HCT) is a strong predictor of relapse. We report our experience using a combination of reduced-dosing clofarabine, CY and etoposide as a 'bridge' to HCT in eight patients with high risk or relapsed ALL and pre-HCT MRD. All patients had detectable MRD (>0.01%, flow cytometry) at the start of therapy with all eight achieving MRD reduction following one cycle. The regimen was well tolerated with seven grade 3/4 toxicities occurring among four of the eight patients. Five patients (62.5%) are alive, one died from relapse (12.5%) and two from transplant-related mortality (25%). The combination of reduced-dose clofarabine, CY and etoposide as bridging therapy appears to be well tolerated in patients with relapsed ALL and is effective in reducing pre-HCT MRD.

Hematopoietic stem cell transplantation for children with high-risk acute lymphoblastic leukemia in first complete remission: a report from the AIEOP registry

Children with high-risk acute lymphoblastic leukemia in first complete remission can benefit from allogeneic hematopoietic stem cell transplantation. We analyzed the outcome of 211 children with high-risk acute lymphoblastic leukemia in first complete remission who were given an allogeneic transplant between 1990 and 2008; the outcome of patients who, despite having an indication for transplantation and a suitable donor, did not receive the allograft for different reasons in the same time period was not analyzed. Sixty-nine patients (33%) were transplanted between 1990 and 1999, 58 (27%) between 2000 and 2005, and 84 (40%) between 2005 and 2008. A matched family donor was employed in 138 patients (65%) and an unrelated donor in 73 (35%). The 10-year probabilities of overall and disease-free survival were 63.4% and 61%, respectively. The 10-year cumulative incidences of transplantation-related mortality and relapse were 15% and 24%, respectively. After 1999, no differences in either disease-free survival or transplant-related mortality were observed in patients transplanted from unrelated or matched family donors. In multivariate analysis, grade IV acute graft-versus-host disease was an independent factor associated with worse disease-free survival. By contrast, grade I acute graft-versus-host disease and age at diagnosis between 1 and 9 years were favorable prognostic variables. Our study, not intended to evaluate whether transplantation is superior to chemotherapy for children with acute lymphoblastic leukemia in first complete remission and high-risk features, shows that the allograft cured more than 60% of these patients; in the most recent period, the outcome of recipients of grafts from matched family and unrelated donors was comparable.

Prognostic and therapeutic implications of minimal residual disease at the time of transplantation in acute leukemia

Relapse remains the major cause of treatment failure after hematopoietic cell transplantation (HCT) in acute leukemia, even in patients transplanted in morphologic CR. Various techniques now enable the sensitive quantification of 'minimal' amounts of residual disease (MRD) in patients with acute leukemia in remission. Numerous studies convincingly demonstrate that MRD at the time of transplantation is a powerful, independent predictor of subsequent relapse, with current detection levels of one leukemic cell in 10(5)-10(6) normal cells being prognostically relevant. This recognition provides the rationale to assign patients with detectable MRD (that is, 'MRD(+)' patients) to intensified therapies before, during, or after transplantation, although data supporting these strategies are still sparse. Limited evidence from observational studies suggests that outcomes with autologous HCT are so poor that MRD(+) patients should preferentially be assigned to allogeneic HCT, which can cure a subgroup of these patients, particularly if unmanipulated (T-cell replete) grafts and/or minimized immunosuppression are used to optimize the graft-vs-leukemia effect. Emerging data suggest that additional therapy with non-cross-resistant agents to decrease residual tumor burden before transplantation in MRD(+) patients might be beneficial. Further, other studies hint at immunotherapy (for example, rapid withdrawal of immunosuppression and/or donor lymphocyte infusions) as a means to prevent overt relapse if patients remain, or become, MRD(+) after HCT. Ultimately, controlled clinical studies are needed to define the value of MRD-directed therapies, and patients should be encouraged to enter such trials.