Minimal Residual Disease and Childhood Leukemia: Standard of Care Recommendations From the Pediatric Oncology Group of Ontario MRD Working Group

Muramyl dipeptide CD10 monoclonal antibody immunoconjugates inhibited acute leukemia in nude mice

Minimal residual disease (MRD) is one of the causes of leukemia recurrence. Previously, we developed anti-CD10 mAb conjugated to muramyl dipeptide immunoconjugate (MDP-Ab) for immune enhancement. The present study aimed to investigate anti-leukemia effect of MDP-Ab administered via different methods in leukemia ectopic graft nude mouse model. BALB/c nude mice were injected with Nalm-6 cells subcutaneously to establish leukemia xenografts in nude mice as a model. MDP-Ab or/and human lymphocytes (LYM) was injected into different sites of the nude mice. Immunohistochemistry staining of CDs in the bone marrow, liver and spleen was performed. IFN-γ was detected by ELISA. We detected the metastasis of leukemia cells to the liver, spleen and bone marrow in nude mouse leukemia model. MDP-Ab and LYM inhibited the growth of tumors, and simultaneous injection of MDP-Ab and LYM into the tumor inhibited the growth of tumors. IFN-γ levels in MDP-Ab (ca) + h-LYM (ca) group, MDP-Ab (ca) + h-LYM (ip) group, MDP-Ab (iv) + h-LYM (ip) group and PBS (ca) + h-LYM (ca) group were significantly higher than those in control group, while IFN-γ level in MDP-Ab (ca) + h-LYM (ca) group was the highest. Moreover, MDP-Ab and h-LYM promoted the expression of hCD4 and hCD8, with the highest expression in MDP-Ab (ca) + h-LYM (ca) group. In conclusion, MDP-Ab effectively promoted the production of IFN-γ, enhanced the antitumor immunity of T lymphocytes and inhibited leukemia.

Impact of minimal residual disease on relapse in childhood acute lymphoblastic leukemia: Lessons learnt from a tertiary cancer center in India

Prognostic predictive value of end of induction minimal residual disease (EOI-MRD) is well established in acute lymphoblastic leukemia (ALL). We evaluated the factors likely to affect EOI-MRD positivity (>0.01%) by flow cytometry and relapse in different BFM-95 (Berlin-Frankfurt-Munich) risk groups among children and adolescents. In this retrospective study, data of 223 newly diagnosed patients with ALL was analyzed. Association between demographic and pretreatment characteristics with EOI-MRD was assessed. Risk factors for relapse were analyzed using univariate and multivariate Cox regression. Proportion of the SR (standard risk), MR (moderate risk), and HR (high risk) patients was 18.8%, 60.9%, 20.3%, respectively. Positive EOI-MRD among these risk groups was observed in 11.9%, 18.3%, and 55.5% patients respectively (p value <.01%). MRD positivity was more likely to be associated with older age (>10 years) and BFM-HR patients (p value .0008 and <.0001). Thirty-four (15.2%) patients relapsed in the whole cohort. On univariate analysis, statistically significant factors for RFS (relapse-free survival) included hyperleukocytosis, high-risk cytogenetics, NCI (National Cancer Institute) high risk, poor day-8 prednisolone response, BFM-HR and positive EOI-MRD status. Of all these only EOI-MRD retained its impact by multivariate analysis. Positive EOI-MRD significantly predicted relapse in BFM-MR with 5-year RFS of 88.0% and 68.4% (p value .02). Five-year RFS of EOI-MRD negative and positive groups were 86.4% and 65.5%, respectively (p value .004). EOI-MRD is a powerful tool to predict relapse in children and adolescent with ALL especially in BFM-MR. Application of MRD in HR patients needs to be redefined in conjunction with other variables.

Laboratory Aspects of Minimal / Measurable Residual Disease Testing in B-Lymphoblastic Leukemia

Minimal residual disease detection provides critical prognostic predictor of treatment outcome and is the standard of care for B lymphoblastic leukemia. Flow cytometry-based minimal residual disease detection is the most common test modality and has high sensitivity (0.01%) and a rapid turnaround time (24 hours). This article details the leukemia associated immunophenotype analysis approach for flow cytometry-based minimal residual disease detection used at St. Jude Children's Research Hospital and importance of using guide gates and back-gating.

Phase 1b study of carfilzomib with induction chemotherapy in pediatric relapsed/refractory acute lymphoblastic leukemia

BACKGROUND

Acute lymphoblastic leukemia (ALL) is the most common cancer diagnosed in childhood. Survival for patients following relapse remains poor, and achieving complete remission (CR) after relapse is the first critical step to cure. Carfilzomib is a proteasome inhibitor with an acceptable safety profile and clinical activity in adults with multiple myeloma but has not been assessed in children. The primary objective of this phase 1b study was to assess the safety and tolerability of carfilzomib combined with vincristine, dexamethasone, asparaginase, and daunorubicin (VXLD) in children with relapsed and/or refractory ALL.

METHODS

Patients aged 1-21 years (n = 24) received 4-week induction therapy with carfilzomib at dose levels of 27 mg/m² (n = 3), 36 mg/m² (n = 7), 45 mg/m² (n = 4), and 56 mg/m² (n = 10) in combination with VXLD. Patients achieving stable disease were offered further consolidation chemotherapy. Analyses were based on the safety evaluable population.

RESULTS

Following dose escalation of carfilzomib, the recommended phase 2 carfilzomib dose was identified as 56 mg/m² . Grade ≥3 hematological adverse events were common (83%, 20/24 patients), and serious treatment-emergent adverse events occurred in 58% (14/24) of patients. At the end of induction, CR/CR with incomplete platelet recovery (CRp)/CR with incomplete blood count recovery (CRi) was identified in 50% of patients (n = 12/24). By the end of consolidation, cumulative CR/CRp/CRi was identified in 58% of patients (n = 14/24).

CONCLUSION

These data support the use of carfilzomib in pediatric patients with relapsed and/or refractory ALL.

Leukemia Stem Cell Frequency at Diagnosis Correlates With Measurable/Minimal Residual Disease and Impacts Survival in Adult Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a heterogenous disease in which the initiation and maintenance of the malignant clone is blamed on a rare population of leukemia stem cells (LSCs). The persistence of such a malignant population is referred to as measurable/minimal residual disease (MRD). Evaluation of MRD is the gold standard for follow-up of therapy and constitutes an independent prognostic parameter. As LSCs are the main contributor to the persistence of MRD, then MRD should correlate with the bulk of LSCs at the individual case level. MRD is measured at defined time points during therapy. However, LSCs can be evaluated at diagnosis, which ensures the advantage of early prediction of high-risk patients and allows for early therapeutic decisions. Using two simple four-color monoclonal antibody combinations (CD38/CD123/CD34/CD45 and CD90/CD133/CD45/CD33) and the prism function of the Coulter Navios flow cytometer, the frequency of LSC subsets was evaluated in 84 newly diagnosed adult AML patients. For each panel, 16 possible combinations were detected. Our results showed that there was extreme variability in the percentage of the LSC fraction between different cases, as well as at the individual case level. For each LSC subset, the median value was used to divide cases into low and high expressors. LSC subsets that showed an impact on overall survival (OS) and disease-free survival (DFS) included CD123+, CD 123+/CD34-, CD34-/CD38+/CD123+, CD34+/CD38-/CD123+, CD133+, and CD133+/CD33-. On multivariate analysis, only CD123 (p ≤ 0.001, SE = 0.266, HR = 2.8, 95% CI = 1.74.7) and CD133+/CD33- (p = 0.017, SE = 0.263, HR = 1.9, 95% CI = 1.1–3.1) retained their significance for OS. Likewise, only CD34+/CD38-/CD123+ (p ≤ 0.001, HR 2.3, SE: 0.499, 95% CI: 2.4–17.4) and CD133 (p = 0.015, HR 2.3, SE 0.34, 95% CI: 1.2–4.4) retained their statistical significance for DFS. The LSC frequency at diagnosis showed a moderate to strong correlation with MRD status at day 14 and day 28. In conclusion, the level of LSCs at diagnosis correlated with MRD status at day 14 and day 28 in AML patients and had a deleterious impact on OS and DFS. It may be used as an early marker for high-risk patients allowing for early therapeutic decisions.

Efficacy and toxicity of high-risk therapy of the Dutch Childhood Oncology Group in childhood acute lymphoblastic leukemia

BACKGROUND

Children with acute lymphoblastic leukemia (ALL) and high-risk (HR) features have a poor outcome and are treated with HR blocks, often followed by allogenic stem cell transplantation (SCT).

PROCEDURE

This article analyses the outcomes of children treated with HR blocks between 2004 and 2017 according to DCOG ALL10/11 protocols. 1297 patients with newly diagnosed ALL were consecutively enrolled, of which 107 met the HR criteria (no complete remission; minimal residual disease (MRD) > 10^-3 after consolidation; "MLL-AF4" translocation and in ALL-10 also poor prednisone response). Patients were treated with one induction and consolidation course followed by three HR chemotherapy blocks, after which they received either SCT or further chemotherapy. MRD levels were measured at end of induction, consolidation, and after each HR block.

RESULTS

At five years, the event-free survival was 72.8% (95% CI, 64.6-82.0), and the cumulative incidence of relapse was 13.0% (95% CI, 6.3-19.8). Patients with only negative or low-positive MRD levels during HR blocks had a significantly lower five-year cumulative incidence of relapse (CIR) of 2.2% (95% CI, 0-6.6) compared with patients with one or more high-positive MRD levels (CIR 15.4%; 95% CI, 3.9-26.9). During the entire treatment protocol, 11.2% of patients died due to toxicity.

CONCLUSIONS

The high survival with HR blocks seems favorable compared with other studies. However, the limit of treatment intensification might have been reached as the number of patients dying from leukemia relapse is about equal as the number of patients dying from toxicity. Patients with negative or low MRD levels during HR blocks have lower relapse rates.

The methods and advances of adaptive immune receptors repertoire sequencing

The adaptive immune response is a powerful tool, capable of recognizing, binding to, and neutralizing a vast number of internal and external threats via T or B lymphatic receptors with widespread sets of antigen specificities. The emergence of high-throughput sequencing technology and bioinformatics provides opportunities for research in the fields of life sciences and medicine. The analysis and annotation for immune repertoire data can reveal biologically meaningful information, including immune prediction, target antigens, and effective evaluation. Continuous improvements of the immunological repertoire sequencing methods and analysis tools will help to minimize the experimental and calculation errors and realize the immunological information to meet the clinical requirements. That said, the clinical application of adaptive immune repertoire sequencing requires appropriate experimental methods and standard analytical tools. At the population cell level, we can acquire the overview of cell groups, but the information about a single cell is not obtained accurately. The information that is ignored may be crucial for understanding the heterogeneity of each cell, gene expression and drug response. The combination of high-throughput sequencing and single-cell technology allows us to obtain single-cell information with low-cost and high-throughput. In this review, we summarized the current methods and progress in this area.

Laboratory Aspects of Minimal / Measurable Residual Disease Testing in B-Lymphoblastic Leukemia

Minimal residual disease detection provides critical prognostic predictor of treatment outcome and is the standard of care for B lymphoblastic leukemia. Flow cytometry-based minimal residual disease detection is the most common test modality and has high sensitivity (0.01%) and a rapid turnaround time (24 hours). This article details the leukemia associated immunophenotype analysis approach for flow cytometry-based minimal residual disease detection used at St. Jude Children's Research Hospital and importance of using guide gates and back-gating.

Caloric and nutrient restriction to augment chemotherapy efficacy for acute lymphoblastic leukemia: the IDEAL trial

Being overweight or obese (OW/OB) during B-cell acute lymphoblastic leukemia (B-ALL) induction is associated with chemoresistance as quantified by minimal residual disease (MRD). We hypothesized that caloric and nutrient restriction from diet/exercise could lessen gains in fat mass (FM) and reduce postinduction MRD. The Improving Diet and Exercise in ALL (IDEAL) trial enrolled patients 10 to 21 years old, newly diagnosed with B-ALL (n = 40), in comparison with a recent historical control (n = 80). Designed to achieve caloric deficits ≥20% during induction, reduce fat intake/glycemic load, and increase activity, IDEAL's end points were FM gain (primary), MRD ≥0.01%, and adherence/feasibility. Integrated biology explored biomarkers of OW/OB physiology. IDEAL intervention did not significantly reduce median FM change from baseline overall (+5.1% [interquartile range [IQR], 15.8] vs +10.7% [IQR, 16.0]; P = .13), but stratified analysis showed benefit in those OW/OB (+1.5% [IQR, 6.6] vs +9.7% [IQR, 11.1]; P = .02). After accounting for prognostic factors, IDEAL intervention significantly reduced MRD risk (odds ratio, 0.30; 95% confidence interval, 0.09-0.92; P = .02). The trial exceeded its adherence (≥75% of overall diet) and feasibility (≥80% completed visits) thresholds. Integrated biology found the IDEAL intervention increased circulating adiponectin and reduced insulin resistance. The IDEAL intervention was feasible, decreased fat gain in those OW/OB, and reduced MRD. This is the first study in any hematologic malignancy to demonstrate potential benefit from caloric restriction via diet/exercise to augment chemotherapy efficacy and improve disease response. A prospective, randomized trial is warranted for validation. These trials were registered at www.clinicaltrials.gov as #NCT02708108 (IDEAL trial) and #NCT01317940 (historical control).

Complete Peripheral Blast Clearance is Superior to the Conventional Cut-Off of 1000/µL in Predicting Relapse in Pediatric Pre-B Acute Lymphoblastic Leukemia

Risk-stratification has contributed to a dramatic improvement in survival in pediatric acute lymphoblastic leukemia (ALL). This study evaluated the utility of prephase response and day 15 bone marrow when a minimal residual disease (MRD) assessment was available. A file review of children aged ≤ 15 years diagnosed with precursor-B ALL from 2014 to 2019 was performed. The protocol used for risk stratification and treatment was based on a UKALL-2003 backbone. All patients received one week of prephase therapy comprised of intravenous dexamethasone in the first 48 h followed by oral prednisolone. The median age of the 255 patients in the study was 5 years. Following the prephase, the peripheral blood absolute blast count was 0 and ≥ 1000/µL blasts in 141 (56%) and 29 (11%), respectively. Ten of 199 (5%) patients with an evaluable day 15 bone marrow had M3 status. At the end of induction, 30 (12%), 127 (50%) and 98 (38%) patients belonged to the standard-risk, intermediate-risk and high-risk (HR) groups, respectively. An M3 day15 bone marrow was the sole reason for escalation in three (3%) of the patients in the HR group. A lack of complete clearance of peripheral blood blasts post-prephase [HR: 2.45 (1.04-5.75), p = 0.040] and a positive MRD [HR: 3.00 (1.28-7.02), p = 0.011] independently predicted risk of relapse. Complete blast clearance is superior to the traditional cut-off of 1000/µL in predicting relapse. The role of a day 15 bone marrow morphology is diminished when an end of induction MRD is available.

Statistics and measurable residual disease (MRD) testing: uses and abuses in hematopoietic cell transplantation

SERIES EDITORS' NOTE

The decision whether to recommend a transplant to someone with acute leukemia in first remission is complex and challenging. Diverse, often confounded co-variates interact to influence one's recommendation. Briefly, the decision metric can be viewed in three spheres: (1) subject-; (2) transplant-; and (3) disease-related co-variates. Subject-related co-variates include items such as age and comorbidities. Transplant-related co-variates include items such as donor-types, graft source, proposed conditioning and pre- and post-transplant immune suppression.But what of disease-related variables? Previously haematologists relied on co-variates such as WBC at diagnosis, chemotherapy cycles to achieve first remission, cytogenetics and most recently, mutation topography. However, these co-variates have largely been replaced by results of measurable residual disease (MRD)-testing. Many chemotherapy-only and transplant studies report strong correlations between results of MRD-testing on therapy outcomes such as cumulative incidence of relapse (CIR), leukemia-free survival (LFS) or survival. (CIR makes biological sense in a transplant context whereas LFS and survival do not give competing causes of death such as transplant-related mortality (TRM), graft-versus-host disease and interstitial pneumonia unrelated to relapse probability).This raises the question of how useful results are of MRD-testing in predicting CIR after transplants. Elsewhere we discussed accuracy and precision of MRD-testing in predicting outcomes of therapy of acute myeloid leukemia (Estey E, Gale RP. Leukemia 31:1255-1258, 2017; Hourigan CS, Gale RP, Gormley NJ, Ossenkoppele GJ, Walter RB. Leukemia 31:1482-1490, 2017). Briefly put, not terribly good. Although results of MRD-testing are often the most powerful predictor of CIR in multivariable analyses, the C-statistic (a measure of prediction accuracy) is often only about 0.75. This is much better than flipping a fair coin but far from ideal.In the typescript which follows, Othus and colleagues discuss statistical issues underlying MRD-testing in the context of haematopoietic cell transplants. We hope readers, especially haematologists who often need to make transplant recommendations to people with acute leukemia in first remission, will read it carefully and critically. The bottom line is MRD-test data are useful but considerable uncertainty is unavoidable with substantial false-positive and -negative rates. We need to acknowledge this uncertainty to ourselves and to the people we counsel. The authors quote Voltaire who said: Doubt is not a pleasant condition, but certainty is an absurd one. Sadly so, but we do the best we can. Robert Peter Gale, Imperial College London, and Mei-Jie Zhang, Medical College of Wisconsin and CIBMTR.

[Prognostic significance and risk factors of minimal residual disease ≥1% on 19th day of induction chemotherapy in children with acute lymphoblastic leukemia]

OBJECTIVE

To assess the prognostic value of minimal residual disease on 19th day of induction chemotherapy (D19 MRD) and the risk factors of D19 MRD ≥ 1% in children with acute lymphoblastic leukemia (ALL) treated following the Chinese Children's Cancer Group ALL protocol.

METHODS

We retrospectively analyzed the data of 243 children with ALL diagnosed between January 1, 2015 and December 31, 2018 in the Department of Pediatrics of Nanfang Hospital (Guangzhou China). Kaplan Meier-survival analysis was performed to compare the survival time between the patients with D19 MRD < 1% and those with D19 MRD ≥ 1%; logistic regression analyisis and Chi-square test were used to identify the risk factors of D19 MRD ≥ 1%.

RESULTS

Compared with those with D19 MRD ≥ 1%, the children with D19 MRD < 1% had significantly better 3-year overall survival (100% vs 90.2%, P=0.004) and event-free survival (97.6% vs 71.6%, P < 0.001). Univariate analysis showed that the odds ratio (OR) for mediastinal invasion, T-cell immunophenotype, TEL/AML1 fusion gene and the presence of blasts in peripheral blood on the 5th day were 4.47 (95%CI: 0.275-72.968, P=0.034), 5.250 (95%CI: 1.950-14.133, P=0.02), 0.330 (95%CI: 0.112-0.970, P=0.036) and 4.407 (95%CI: 1.782-10.895, P=0.01), respectively. The initial risk stratification (P < 0.001), white blood cell grades (P=0.018) and its counts (P=0.027), and the number of blasts on the 5th day (P < 0.001) were significantly different between the two groups. Multivariate analysis showed that initial risk stratification as intermediate and high risks (OR=2.889, 95% CI: 1.193-6.996) and the presence of blasts in peripheral blood on the 5th day (OR=4.477, 95% CI: 1.692-11.843) were independent risk factors for poor early treatment response.

CONCLUSIONS

D19 MRD ≥ 1% is a predictor of poor prognosis in children with ALL. Mediastinal invasion, T-cell immunophenotype and the presence of blasts in peripheral blood on the 5th day are all risk factors for poor early treatment response, while TEL/AML1 fusion gene is a protective factor; the initial risk stratification as intermediate to high risk and the presence of blasts in peripheral blood on the 5th day are independent risk factors for poor early treatment response of the patients.

Tracing Leukemia Stem Cells and Their Influence on Clinical Course of Adult Acute Myeloid Leukemia

BACKGROUND

Acute myeloid leukemia (AML) evolves from neoplastic transformation of stem cell disease termed "leukemia stem cells" (LSCs). An unsatisfactory response to AML therapy is determined by the presence of minimal residual disease (MRD). The predominance of LSCs might anticipate sustained MRD results. The present study aimed to demonstrate the effect of LSCs on MRD at induction days 14 and 28 on overall survival (OS) and disease-free survival (DFS) and to compare LSC expression with MRD status.

PATIENTS AND METHODS

A total of 84 patients with de novo adult AML underwent testing using LSC panels for CD38/CD123/CD34/CD45 and CD90/CD133/CD45/CD33 and different regular MRD panels.

RESULTS

At day 14 after induction, the high expression of CD123 and CD133 had adverse effects on both OS and DFS (P = .004 and P ≤ .001 and P ≤ .001 and P ≤ .001, respectively). Greater expression of CD34⁺/CD38^-/CD123⁺ resulted in unfavorable OS and DFS (P ≤ .001 for both). Both CD34⁺/CD38^-/CD123⁺ and CD34^-/CD38⁺/CD123⁺ expression at day 14 after induction had an adverse effect on DFS only (P < .001 and P = .029, respectively). On multivariate analysis, CD133 expression and MRD status were independent prognostic parameters (hazard ratio [HR], 2.3; 95% confidence interval [CI], 1.2-4.4; P = .015; and HR, 2.9; 95% CI, 1.0-7.9; P = .041). At day 28 after induction, MRD and increased CD123⁺/CD34^-, CD34⁺/CD38^-/CD123⁺, CD133⁺/CD33^- expression were associated with inferior OS (P = .016, P = .0035, P = .0.002, and P = .002, respectively). MRD and high expression of CD34⁺CD123⁺, CD133⁺/CD33^-, CD34⁺/CD38^-/CD123⁺ were associated with inferior DFS (P < .001, P = .002, P < .001, P < .001, respectively). On multivariate analysis, only CD133⁺/CD33^- expression was the independent prognostic factor (HR, 3.1; 95% CI, 1.5-6.7; P = .003).

CONCLUSIONS

Estimation of LSC expression is a sensitive indicator of the response to therapy in adult patients with AML and might be a better prognosticator than the findings from regular MRD panels.

[Clinical effect of CCLG-ALL2008 regimen in treatment of children and adolescents aged >10 years with acute lymphoblastic leukemia]

OBJECTIVE

To study the long-term clinical effect of CCLG-ALL2008 regimen in the treatment of children and adolescents, aged >10 years, with newly diagnosed acute lymphoblastic leukemia (ALL).

METHODS

A retrospective analysis was performed for the clinical data of 150 ALL children and adolescents aged >10 years who were treated with CCLG-ALL2008 regimen from April 2008 to April 2015. The Kaplan-Meier method was used to analyze overall survival (OS) rate and event-free survival (EFS) rate.

RESULTS

Among the 150 children and adolescents, there were 87 (58.0%) boys and 63 (42.0%) girls, with a median age of 11 years (range 10-15 years). Of the 150 children and adolescents, 84 (56.0%) had intermediate risk and 66 (44.0%) had high risk; 122 (81.3%) had B-lineage acute lymphoblastic leukemia (B-ALL) and 28 (18.7%) had T-lineage acute lymphoblastic leukemia (T-ALL). The fusion gene test yielded positive results in 51 children and adolescents (34.0%), among whom 16 (31%) had positive BCR-ABL, 11 (22%) had positive TEL-AML1, 8 (16%) had positive E2A-PBX1, and 16 (31%) were positive for other fusion genes. The complete remission rate was 96.0% (144/150) after one course of treatment with CCLG-ALL2008 regimen. The median follow-up time was 52 months (range 3-122 months). The 5-year OS rate was 79.0%±3.5%, and the 5-year EFS rate was 67.3%±4.1%. There were no significant differences in 5-year OS and EFS rates between the children with intermediate or high risk, as well as between the children with B-ALL or T-ALL (P>0.05). The children and adolescents who achieved complete remission of bone marrow at the end of induction therapy had significantly higher 5-year OS and EFS rates than those who did not achieve complete remission (P<0.05).

CONCLUSIONS

In ALL children and adolescents aged >10 years, CCLG-ALL2008 regimen can help to achieve high complete remission rate, 5-year OS rate and 5-year EFS rate. The children and adolescents failing to achieve complete remission at the end of induction therapy tend to have a poor prognosis.

Monozygotic twins diagnosed simultaneously with RAM immunophenotype acute myeloid leukemia

AML with the RAM immunophenotype is associated with extremely poor prognosis. We report a rare case of monozygotic twins presenting simultaneously at the age of 2 years with RAM AML. Each twin underwent a myeloablative 7/10 unrelated umbilical cord blood transplant. Pretransplant Twin A's bone marrow was negative for MRD by flow cytometry (<0.01%) unlike Twin B's bone marrow (0.07%). Twin A is alive in remission 3 years from transplant. Twin B developed primary graft failure, but subsequently rescued with a haploidentical stem cell transplant. However, she relapsed and died 13 months from diagnosis. The twins' clinical courses demonstrate that upfront intensive chemotherapy to achieve negative MRD, followed by allogeneic hematopoietic stem cell transplant as postremission intensification strategy, should be considered in this high-risk AML.

Considerations for monitoring minimal residual disease using immunoglobulin clonality in patients with precursor B-cell lymphoblastic leukemia

BACKGROUND

Minimal residual disease (MRD) monitoring is a powerful tool to predict the risk of relapse. Herein, we present an MRD monitoring strategy for B-cell lymphoblastic leukemia (B-ALL) using high-throughput sequencing (HTS) of immunoglobulin (Ig) clonality before implementation into routine practice.

METHODS

We selected 74 bone marrow (BM) specimens from 47 patients who were diagnosed with B-ALL. Ig clonality was analyzed using both fragment analysis and HTS. The performance of Ig clonality was evaluated through comparison of the results from real-time quantitative polymerase chain reaction (qPCR) of leukemia-specific fusion transcripts and flow cytometry.

RESULTS

IGH clonality was observed in all patients, and the sum of clonal burden varied (9.47%-96.77%). IGK clonality was identified in 70% of patients and availed in cases with low IGH clonal burden. The total IGH clonal burden was significantly correlated with the proportion of leukemic blasts, leukemia-specific fusion transcripts, and flow cytometry. We recognized the different responses of each clone and emerging clones originating from the trace of Ig rearrangement presented in the initial specimen. IGH clonal burden after chemotherapy represented patient outcomes well. IGH assay also provided information of repertoire diversity of IGH rearrangement.

CONCLUSION

The Ig clonality assay via HTS will be a promising tool for MRD monitoring of B-ALL through an adequate strategy to identify and monitor individual clones and determine repertoire diversity.

Outcome of children with newly diagnosed acute lymphoblastic leukemia treated with CCLG-ALL 2008: The first nation-wide prospective multicenter study in China

Acute lymphoblastic leukemia (ALL) is the most common malignancy among children. The trial Chinese Children Leukemia Group (CCLG)-ALL 2008 was a prospective clinical trial designed to improve treatment outcome of childhood ALL through the first nation-wide collaborative study in China. Totally 2231 patients were recruited from ten tertiary hospitals in eight cities. The patients were stratified according to clinical-biological characteristics and early treatment response. Standard risk (SR) and intermediate risk (IR) groups were treated with a modified BFM based protocol, and there was 25%-50% dose reduction during intensification phases in the SR group. Patients in high risk (HR) group received a more intensive maintenance treatment. Minimal residual disease (MRD) monitoring with treatment adjustment was performed in two hospitals (the MRD group). Complete remission (CR) was achieved in 2100 patients (94.1%). At five years, the estimate for overall survival (OS) and event-free survival (EFS) of the whole group was 85.3% and 79.9%, respectively. The cumulative incidence of relapse (CIR) was 15.3% at five years. The OS, EFS and CIR for the SR group were 91.5%, 87.9%, and 9.7%, respectively. The outcome of the MRD group is better than the non-MRD group (5y-EFS: 82.4% vs 78.3%, P = .038; 5y-CIR: 10.7% vs 18.0%, P < .001). Our results demonstrated that the large-scale multicenter trial for pediatric ALL was feasible in China. Dose reduction in the SR group could achieve high EFS. MRD-based risk stratification might improve the treatment outcome for childhood ALL.

[Clinical application of minimal residual disease detection in childhood acute leukemia]

In recent years, great progress has been made in the treatment outcome of childhood acute leukemia with the improvement of chemotherapy regimens and the introduction of risk-stratified therapy; however, minimal residual disease (MRD) is still a difficult problem which affects the prognosis of acute leukemia. MRD influences the selection of chemotherapy regimens and recurrence risk stratification, and meanwhile, it can be used for prognostic prediction. At present, flow cytometry and polymerase chain reaction are mainly used for MRD detection. The next-generation sequencing also plays an important role in MRD detection, especially in MRD detection after stem cell transplantation. This article reviews the methodology and significance of MRD detection in childhood acute leukemia.