Minimal residual disease monitoring in childhood acute lymphoblastic leukemia:

Flow cytometric signature of CD371-positive B-cell acute lymphoblastic leukemia

OBJECTIVES

Multiparametric flow cytometry (MFC) aids in the diagnosis and management of B-cell acute lymphoblastic leukemia (B-ALL) by establishing a baseline immunophenotype for leukemic cells and measuring minimal residual disease (MRD) throughout the course of treatment. Aberrant expression patterns of myeloid markers in B-ALL are also examined during long-term surveillance. Here, we investigated the utility of the newly described myeloid marker cluster of differentiation (CD)371 in MRD surveillance via MFC in patients with CD371-positive B-ALL.

METHODS

Eight-color MFC with standard panels (including CD371) was used to evaluate 238 patients with newly diagnosed B-ALL. Expression levels of key markers were retrospectively assessed at diagnosis, as well as days 15 and 33 of therapy.

RESULTS

CD371 was expressed in 8.4% of patients with B-ALL. CD371 positivity was associated with older age at diagnosis, higher expression levels of CD34 and CD38, and lower expression levels of CD10 and CD20. Residual leukemic cells demonstrated decreased CD10 expression and increased CD45 expression after therapy, whereas CD371 expression remained stable.

CONCLUSIONS

Patients with CD371-positive B-ALL exhibit a specific signature that merits further analysis, particularly because it has been associated with DUX4 rearrangement.

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

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

Absence of terminal deoxynucleotidyl transferase expression in T-ALL/LBL accumulates chromosomal abnormalities to induce drug resistance

T-acute lymphoblastic leukemia/lymphoma (T-ALL/LBL) is a malignant neoplasm of immature lymphoblasts. Terminal deoxynucleotidyl transferase (TDT) is a template-independent DNA polymerase that plays an essential role in generating diversity for immunoglobulin genes. T-ALL/LBL patients with TDT^- have a worse prognosis. However, how TDT^- promotes the disease progression of T-ALL/LBL remains unknown. Here we analyzed the prognosis of T-ALL/LBL patients in Shanghai Children's Medical Center (SCMC) and confirmed that TDT^- patients had a higher rate of recurrence and remission failure and worse outcomes. Cellular experiments demonstrated that TDT was involved in DNA damage repair. TDT knockout delayed DNA repair, arrested the cell cycle and decreased apoptosis to induce the accumulation of chromosomal abnormalities and tolerance to abnormal karyotypes. Our study demonstrated that the poor outcomes in TDT^- T-ALL/LBL might be due to the drug resistance (VP16 and MTX) induced by chromosomal abnormalities. Our findings revealed novel functions and mechanisms of TDT in T-ALL/LBL and supported that hematopoietic stem cell transplantation (HSCT) might be a better choice for these patients.

The kinetics of blast clearance are associated with copy number alterations in childhood B-cell acute lymphoblastic leukemia

We analyzed the pattern of whole-genome copy number alterations (CNAs) and their association with the kinetics of blast clearance during the induction treatment among 195 pediatric patients with B-cell precursor acute lymphoblastic leukemia (BCP-ALL) who displayed intermediate or high levels of minimal residual disease (MRD). Using unsupervised hierarchical clustering of CNAs > 5 Mbp, we dissected three clusters of leukemic samples with distinct kinetics of blast clearance [A - early slow responders (n=105), B - patients with persistent leukemia (n=24), C - fast responders with the low but detectable disease at the end of induction (n=66)] that corresponded with the patients' clinical features, the microdeletion profile,the presence of gene fusions and patients survival. Low incidence of large CNAs and chromosomal numerical aberrations occurred in cluster A which included ALL samples showing recurrent microdeletions within the genes encoding transcription factors (i.e., IKZF1, PAX5, ETV6, and ERG), DNA repair genes (XRCC3 and TOX), or harboring chromothriptic pattern of CNAs. Low hyperdiploid karyotype with trisomy 8 or hypodiploidy was predominantly observed in cluster B. Whereas cluster C included almost exclusively high-hyperdiploid ALL samples with concomitant mutations in RAS pathway genes. The pattern of CNAs influences the kinetics of leukemic cell clearance and selected aberrations affecting DNA repair genes may contribute to BCP-ALL chemoresistance.

Minimal residual disease detection by multicolor flow cytometry in cryopreserved ovarian tissue from leukemia patients

Background

Cryopreservation of ovarian tissue is a fertility-preservation option for women before gonadotoxic treatments. However, cryopreserved ovarian tissue transplantation must be performed with caution in women with malignancies that may metastasize to the ovaries. For this purpose, detecting minimal residual disease (MRD) in the ovarian cortex using sensitive methods is a crucial step. We developed an automated ovarian tissue dissociation method to obtain ovarian cell suspensions.

Results

We assessed MRD by multicolor flow cytometry (MFC) in cryopreserved ovarian cortex of 15 leukemia patients: 6 with B-cell acute lymphoblastic leukemia (B-ALL), 2 with T-cell acute lymphoblastic leukemia (T-ALL) and 7 with acute myeloid leukemia (AML). Ovarian MRD was positive in 5 of the 15 leukemia patients (one T-ALL and 4 AML). No B-ALL patient was positive by MFC. Quantitative reverse-transcribed polymerase chain reaction was performed when a molecular marker was available, and confirmed the MFC results for 3 patients tested. Xenografts into immunodeficient mice were also performed with ovarian cortical tissue from 10 leukemia patients, with no evidence of leukemic cells after the 6-month grafting period.

Conclusions

In conclusion, this is the first study using MFC to detect MRD in ovarian cortical tissue from acute leukemia patients. MFC has been accepted in clinical practice for its ease of use, the large number of parameters available simultaneously, and high throughput analysis. We demonstrate here that MFC is a reliable method to detect MRD in cryopreserved ovarian tissue, with a view to controlling the oncological risk before ovarian tissue transplantation in leukemia patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13048-021-00936-4.

Prognostic Observational Analysis of BMI, Leptin, and Adiponectin in Children With Acute Lymphocytic Leukemia Undergoing Remission-Induction Chemotherapy

BACKGROUND

The survival rate of children and adolescents with acute lymphoblastic leukemia (ALL) has progressively improved. However, ALL survivors often have adverse effects after treatment, such as an increased risk of obesity. Obesity has been associated with reduced survival.

OBJECTIVE

We investigated the relationship between obesity, adipocytokine levels, and ALL short-term outcomes.

METHODS

Weight and height were measured, and body mass index (BMI) was calculated at patient diagnosis and discharge. Leptin and Adiponectin levels and Minimal Residual Disease (MRD) were measured before therapy, at days 19 of remission-induction therapy, and at the end of remission-induction therapy (days 46). The relationship between BMI, adipocytokine levels, and MRD was then determined.

RESULTS

Compared to the normal BMI group, children with an abnormal increase in BMI had an increase in MRD at day 19 and 46 (P = 0.04 and P = 0.008), and showed a positive correlation (P = 0.014). In addition, we found a positive correlation between weight, hip circumference at diagnosis and at day 19, and MRD at day 46. Both BMI and fat concentric distribution affected the outcome of ALL children. A higher BMI was also associated with a significant increase in Leptin levels at diagnosis. Leptin resistance should be considered in ALL children with high BMI.

CONCLUSION

BMI affects the outcome of ALL patients. Early interventions such as regular weight, height monitoring, and dietary assessments should be preferably initiated during remission-induction chemotherapy.

Utilizing the prognostic impact of minimal residual disease in treatment decisions for pediatric acute lymphoblastic leukemia

INTRODUCTION

Acute lymphoblastic leukemia (ALL) is the first pediatric cancer where the assessment of early response to therapy by minimal residual disease (MRD) monitoring has demonstrated its importance to improve risk-based treatment approaches. The most standardized tools to study MRD in ALL are multiparametric flow cytometry and realtime-quantitative polymerase chain reaction amplification-based methods. In recent years, MRD measurement has reached greater levels of sensitivity and standardization through international laboratory networks collaboration.

AREAS COVERED

We herewith describe how to assess and apply the prognostic impact of MRD in treatment decisions, with specific focus on pediatric ALL. We also highlight the role of MRD monitoring in the context of genetically homogeneous subgroups of pediatric ALL. However, some queries remain to be addressed and emerging technologies hold the promise of improving MRD detection in ALL patients.

EXPERT OPINION

Emerging technologies, like next generation flow cytometry, droplet digital PCR, and next generation sequencing appear to be important methods for assessing MRD in pediatric ALL. These more specific and/or sensitive MRD monitoring methods may help to predict relapse with greater accuracy, and are currently being used in clinical trials to improve pediatric ALL outcome by optimizing patient stratification and earlier MRD-based interventional therapy.

Reduced-intensity therapy for pediatric lymphoblastic leukemia: impact of residual disease early in remission induction

Legacy data show that ∼40% of children with acute lymphoblastic leukemia (ALL) were cured with limited antimetabolite-based chemotherapy regimens. However, identifying patients with very-low-risk (VLR) ALL remains imprecise. Patients selected based on a combination of presenting features and a minimal residual disease (MRD) level <0.01% on day 19 of induction therapy had excellent outcomes with low-intensity treatment. We investigated the impact of MRD levels between 0.001% and <0.01% early in remission induction on the outcome of VLR ALL treated with a low-intensity regimen. Between October of 2011 and September of 2015, 200 consecutive patients with B-precursor ALL with favorable clinicopathologic features and MRD levels <0.01%, as assessed by flow cytometry in the bone marrow on day 19 and at the end of induction therapy, received reduced-intensity therapy. The 5-year event-free survival was 89.5% (± 2.2% standard error [SE]), and the overall survival was 95.5% (± 1.5% SE). The 5-year cumulative incidence of relapse (CIR) was 7% (95% confidence interval, 4-11%). MRD levels were between 0.001% and <0.01% on day 19 in 29 patients. These patients had a 5-year CIR that was significantly higher than that of patients with undetectable residual leukemia (17.2% ± 7.2% vs 5.3% ± 1.7%, respectively; P = .02). Our study shows that children with VLR ALL can be treated successfully with decreased-intensity therapy, and it suggests that the classification criteria for VLR can be further refined by using a more sensitive MRD assay.

Combined use of peripheral blood blast count and platelet count during and after induction therapy to predict prognosis in children with acute lymphoblastic leukemia

Several studies have reported an association between the rapidity of reduction in peripheral blood blast count or recovery of normal hematopoiesis and treatment outcome during therapy in children with acute lymphoblastic leukemia (ALL). However, little is known about the impact of both of these aspects on prognosis in pediatric ALL. Accordingly, the purpose of this study was to evaluate whether the combined use of blood blast count and platelet count could predict event-free survival (EFS) and overall survival (OS) when minimal residual disease (MRD) detection was not available.A total of 419 patients aged 0 to 14 years diagnosed and treated for ALL between 2011 and 2015 were enrolled.Patients with a blast count ≥0.1 × 109/L on day 8 exhibited significantly lower survival rates than that in those with blast counts <0.1 × 109/L. The EFS and OS in patients with platelet count ≥100 × 109/L on day 33 were significantly higher than those with platelet counts <100 × 109/L. In univariate and multivariate analyses, patients with low blast count on day 8 and high platelet count on day 33 were significantly associated with better EFS and OS. The combination of blast cell count on day 8 and platelet count on day 33 demonstrated a strong association with MRD-based risk stratification.Complete blood count is an inexpensive, easy to perform, and reliable measurement in children with ALL. The combination of blast count and platelet count during and after induction chemotherapy was a significant and independent prognostic factor for treatment outcome in pediatric ALL.

Clinical features and outcome of pediatric acute lymphoblastic leukemia with low peripheral blood blast cell count at diagnosis

Peripheral blood (PB) blast cell count on day 8 of prednisone therapy has been considered one of the strongest predictors of outcome in children with acute lymphoblastic leukemia (ALL). However, little is known about the clinical features and prognostic impact of PB blast cell count at diagnosis in these patients. The aim of this study was to evaluate the relationship between initial PB blast cell count and clinical prognosis of pediatric ALL.The study comprised 367 patients with ALL, aged 0 to 14 years, enrolled and treated using the Chinese Children's Leukemia Group-ALL 2008 protocol between 2011 and 2015. The majority (91.6%) of patients were B-cell precursor ALL (BCP ALL), and 8.4% were T-cell ALL (T-ALL).Patients with BCP ALL in the low PB blast cell count group (<1 × 109/L) had significantly superior survival rates to those in the high count group (≥30 × 109/L). In T-ALL, the low count group showed significantly inferior survival rates compared to both the intermediate count group (1-29.9 × 109/L) and high count group. Multivariate analysis revealed that the initial white blood cell count and minimal residual disease at the end of induction therapy were independently predictive of BCP ALL outcome, while risk stratification was shown to be an independent prognostic factor for T-ALL outcome.These results indicated that low blast cell count in PB at diagnosis was associated with different clinical outcomes in patients with BCP ALL and T-ALL, although it was not an independent outcome predictor by multivariate analysis.

Clinical Significance of Minimal Residual Disease at the End of Remission Induction Therapy in Childhood Acute Lymphoblastic Leukemia

BACKGROUND

Detection of minimal residual disease (MRD) in the early phase of therapy is the most powerful predictor of relapse risk in children with acute lymphoblastic leukaemia (ALL).

AIM

We aimed to determine the significance of MRD at the end of remission induction therapy in the prediction of treatment outcome in children with ALL.

METHODS

Sixty-four consecutive patients aged 1-14 years with newly diagnosed ALL were enrolled in this study from January 2010 to October 2017. All patients were treated according to the ALL IC BFM 2002 protocol. MRD was detected at the end of remission induction therapy (day 33) by multiparameter 6-colour flow cytometry performed on bone marrow specimens with a sensitivity of 0.01%.

RESULTS

Overall, 42.2% of patients had detectable MRD on day 33 of therapy. MRD measurements were not significantly related to presenting characteristics but were associated with a poorer blast clearance on day 8 and 15 of remission induction therapy. Patients with negative MRD status on day 33 had a 5-year event-free survival of 94.6% compared with 76.1% for those with positive MRD status (P = 0.044).

CONCLUSION

MRD levels at the end of remission induction therapy measured by multiparameter flow cytometry have clinical significance in childhood ALL. High levels of MRD are strongly related to poor treatment outcome.

Comparison between flow cytometry and standard PCR in the evaluation of MRD in children with acute lymphoblastic leukemia treated with the GBTLI LLA - 2009 protocol

Minimal residual disease (MRD) monitoring is of prognostic importance in childhood acute lymphoblastic leukemia (ALL). The detection of immunoglobulin and T-cell receptor gene rearrangements by real-time quantitative PCR (RT-PCR) is considered the gold standard for this evaluation. However, more accessible methods also show satisfactory performance. This study aimed to compare MRD analysis by four-color flow cytometry (FC) and qualitative standard PCR on days 35 and 78 of chemotherapy and to correlate these data with patients' clinical characteristics. Forty-two children with a recent diagnosis of ALL, admitted to a public hospital in Brazil for treatment in accordance with the Brazilian Childhood Cooperative Group for ALL Treatment (GBTLI LLA-2009), were included. Bone marrow samples collected at diagnosis and on days 35 and 78 of treatment were analyzed for the immunophenotypic characterization of blasts by FC and for the detection of clonal rearrangements by standard PCR. Paired analyses were performed in 61/68 (89.7%) follow-up samples, with a general agreement of 88.5%. Disagreements were resolved by RT-PCR, which evidenced one false-negative and four false-positive results in FC, as well as two false-negative results in PCR. Among the prognostic factors, a significant association was found only between T-cell lineage and MRD by standard PCR. These results show that FC and standard PCR produce similar results in MRD detection of childhood ALL and that both methodologies may be useful in the monitoring of disease treatment, especially in regions with limited financial resources.

Clinical benefit of a high-throughput sequencing approach for minimal residual disease in acute lymphoblastic leukemia

The molecular detection of minimal residual disease (MRD) is standard of care in acute lymphoblastic leukemia to personalize the stratification of patients to appropriate intensity chemotherapy regimens. High-throughput sequencing (HTS) techniques are driving changes to MRD methodologies. Our study demonstrates HTS can identify suitable diagnostic markers, even in cases where traditional screening has been unsuccessful. Markers identified by HTS were used to track MRD using standard real-time quantitative PCR. We show, with six patient examples, clinical benefits of utilizing HTS to screen diagnostic samples and its necessity when traditional screening techniques fail. This is practical evidence that current MRD diagnostic marker screening should be replaced by an HTS approach.

Reassessment of the Risk-stratified GD-2008 ALL Protocol

OBJECTIVE

To explore the clinical features and outcomes of relapsed childhood acute lymphoblastic leukemia (ALL) at our center, achieve the early detection of risk factors for recurrence and assess the risk-stratified Guangdong (GD)-2008 ALL protocol.

MATERIALS AND METHODS

In total, 59 Chinese childhood ALL patients treated with the GD-2008 ALL protocol who relapsed between July 2008 and March 2015 were enrolled in this study. Their clinical features and outcomes were retrospectively analyzed and compared with those of 218 patients who achieved continuous complete remission.

RESULTS

Of the 285 study participants, 8 died of treatment-related infections or other complications before remission, 218 achieved continuous complete remission, and 59 patients relapsed, yielding a relapse rate of 20.7%. The number of relapsed patients in the standard-risk, intermediate-risk, and high-risk groups were 15 (17.0%), 27 (19.7%), and 17 (32.7%), respectively. Risk factors included age 10 years and above at first diagnosis, white blood cell (WBC) count ≥50×10/L, poor prednisone response, failure to achieve bone marrow complete remission at day 15 of induction chemotherapy. High-risk stratification and a high level (≥0.1%) of minimal residual disease at day 33 were the risk factors for relapse. Multivariate analysis showed that a high WBC at first diagnosis was an independent risk factor for relapse (P=0.000).

CONCLUSION

For the GD-2008 ALL risk stratification based on age and initial WBC, 10 years of age and WBC 50×10/L can be used as cut-offs. Patients at high risk benefited from the GD-2008 ALL protocol. In addition, the impact of minimal residual disease on prognosis should be considered.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Differential expression of CD73, CD86 and CD304 in normal vs. leukemic B-cell precursors and their utility as stable minimal residual disease markers in childhood B-cell precursor acute lymphoblastic leukemia

BACKGROUND

Optimal discrimination between leukemic blasts and normal B-cell precursors (BCP) is critical for treatment monitoring in BCP acute lymphoblastic leukemia (ALL); thus identification of markers differentially expressed on normal BCP and leukemic blasts is required.

METHODS

Multicenter analysis of CD73, CD86 and CD304 expression levels was performed in 282 pediatric BCP-ALL patients vs. normal bone marrow BCP, using normalized median fluorescence intensity (nMFI) values.

RESULTS

CD73 was expressed at abnormally higher levels (vs. pooled normal BCP) at diagnosis in 71/108 BCP-ALL patients (66%), whereas CD304 and CD86 in 119/202 (59%) and 58/100 (58%) patients, respectively. Expression of CD304 was detected at similar percentages in common-ALL and pre-B-ALL, while found at significantly lower frequencies in pro-B-ALL. A significant association (p = 0.009) was found between CD304 expression and the presence of the ETV6-RUNX1 fusion gene. In contrast, CD304 showed an inverse association with MLL gene rearrangements (p = 0.01). The expression levels of CD73, CD86 and CD304 at day 15 after starting therapy (MRD15) were stable or higher than at diagnosis in 35/37 (95%), 40/56 (71%) and 19/41 (46%) cases investigated, respectively. This was also associated with an increased mean nMFI at MRD15 vs. diagnosis of +24 and +3 nMFI units for CD73 and CD86, respectively. In addition, gain of expression of CD73 and CD86 at MRD15 for cases that were originally negative for these markers at diagnosis was observed in 16% and 18% of cases, respectively. Of note, CD304 remained aberrantly positive in 63% of patients, despite its levels of expression decreased at follow-up in 54% of cases.

CONCLUSIONS

Here we show that CD73, CD86 and CD304 are aberrantly (over)expressed in a substantial percentage of BCP-ALL patients and that their expression profile remains relatively stable early after starting therapy, supporting their potential contribution to improved MRD analysis by flow cytometry.

No prognostic significance of immunophenotypic changes at the end of remission induction therapy in children with B-lineage acute lymphoblastic leukemia

Detection of aberrant antigen expression in acute lymphoblastic leukemia (ALL) by flow cytometric is proposed for the quantification of minimal residual disease (MRD). There are few studies that investigate the stability of the antigen expression in children with B lineage ALL at the end of remission induction therapy and determine its prognostic impact. Between 2010 and 2015, 691 bone marrow specimens of childhood ALL were sent at diagnosis for immunophenotypic characterization, and follow-up samples for MRD were analyzed on day 33. Of these, 155 patients with MRD more than or equal to 0.01% were eligible for the study. Immunophenotypic studies were performed by multiparametric flow cytometry using four-colour monoclonal antibody combinations. Overall, 86 of 155 (55.5%) cases showed phenotype shifts at least one marker. CD19 was the most stable markers. By contrast, CD20 was significantly different between diagnosis and day 33 in nearly one third of the cases. Shifts of antigen expression was not significantly associated with EFS, RFS or OS (P > 0.05). Multivariate analysis showed that WBC and BCR-ABL have independent prognostic value in childhood ALL. Changes in antigen expressions were commonly occurred at the end of induction and not associated with prognostic value in patients whose MRD were positive on day 33.

Immunophenotypic Characterization of Cytogenetic Subgroups in Egyptian Pediatric Patients With B-Cell Acute Lymphoblastic Leukemia

BACKGROUND

Identification of prognostic factors in acute lymphoblastic leukemia (ALL) patients is important for stratifying patients into risk groups and tailoring treatment accordingly. Molecular and cytogenetic abnormalities are the most important prognostic factors. Minimal residual disease (MRD) is also an important predictor of relapse in ALL. However, the correlation of both prognostic variables has not been thoroughly studied.

METHODS

We investigated the correlation between defined cytogenetic abnormalities and selected new MRD markers (CD79b, CD123, and CD200) in 56 newly diagnosed Egyptian pediatric B-cell ALL patients.

RESULTS

CD123 found to be expressed in 45% of patients, CD200 in 80.3%, and CD79b in 67.9%. MRD analysis during treatment showed stable expression patterns of CD200. There was significant association of CD123 expression with the hyperdiploid ALL group (P = .017). Another association (P = .029) was found between CD79b negativity and the t(12;21) group. CD200 was widely expressed in all groups.

CONCLUSION

There is a significant correlation between some markers, and certain ALL recurrent cytogenetic subgroups (CD123 and hyperdiploidy, CD79b negativity, and ETV-RUNX1 group) have good prognostic value. CD200 can be used as MRD markers in ALL patients and can also can serve as therapy targets.

Outcome and Minimal Residual Disease Monitoring in Patients with t(16;21) Acute Myelogenous Leukemia Undergoing Allogeneic Hematopoietic Stem Cell Transplantation

Patients with t(16;21) acute myelogenous leukemia (AML) who receive chemotherapy have poor outcomes. The treatment efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT) must be identified, and the usefulness of minimal residual disease (MRD) monitoring requires evaluation. Fourteen consecutive patients with t(16;21) AML undergoing allo-HSCT at our institution were included in this study. Translocation liposarcoma- ETS-related gene (TLS-ERG) transcript levels were serially monitored for a median of 15 months (range, 3-51 months) after allo-HSCT. Eight patients relapsed, 7 patients died from relapse-related causes, and 1 patient died from a non-relapse-related cause. The 2-year cumulative incidence rates of relapse, disease-free survival, and overall survival after HSCT were 66.2%, 30.8%, and 46.2%, respectively. Of the 3 patients who received an HLA-matched sibling transplant, 2 relapsed, and 1 (33.3%) was in hematologic complete remission (CR) but died of nonrelapse mortality, whereas 5 of 11 patients (45.5%) who received haploidentical transplantation were in CR and were alive. Two of 6 patients with undetectable TLS-ERG at the time of allo-HSCT relapsed, at 14 and 15 months, and 3 of 4 PCR-positive patients relapsed, at a median of 10 months after HSCT. Four patients with continually low post-HSCT TLS-ERG levels (mostly <.01%) remained alive and in CR. The TLS-ERG levels of all 8 patients who relapsed were significantly increased before the relapse, exceeding 1.0% in all 7 patients who experienced hematologic relapse. In total, 7 patients received modified donor lymphocyte infusion (DLI), and 1 patient received IFN-α. All 7 patients with a TLS-ERG level >5.0% at the time of intervention experienced an increase or a brief decrease in TLS-ERG level, followed by an increase, and 6 relapsed, whereas the TLS-ERG level of 1 patient with a TLS-ERG level <1.0% at intervention decreased to undetectable. Therefore, t(16;21) AML is an indication for allo-HSCT. Among the HSCT recipients, 30.8% responded to treatment with CR. TLS-ERG transcript levels reflect MRD and might predict relapse and guide effective intervention.

Detection of minimal residual disease in childhood B-acute lymphoblastic leukemia by 4-color flowcytometry

Monitoring of minimal residual disease (MRD) is currently considered the most powerful predictor of outcome in acute lymphoblastic leukemia (ALL). Achievement of a negative MRD state assessed by multicolor flowcytometry (MFC) is an important predictor of disease-free survival (DFS) and overall survival (OS) in ALL patients. We sought to determine whether panels of antibodies combination are more suitable for detection of MRD in Childhood ALL. Eighty-four (84) patients with ALL (B-lineage subtype) were enrolled in this study. Normal template for B cell precursors was established in 15 control participants using 4-four panels of monoclonal Antibodies (Mo Abs),{CD22, CD45, CD58 and CD97 in combination with CD10, CD19, CD34}. At diagnosis, CD22 exhibited the lowest incidence of expression in only 50% of all patients, while CD45, CD58, and CD97 were expressed in 80.9, 59.5 and 92.8%, respectively. Analysis of MRD was performed for each Mo Abs combination at day 0 and day 14 post-induction of chemotherapy by 4-color (FCM). The incidence of MRD was 61.9, 70.6, 60.0 and 55.1% for CD22, CD45, CD58 and CD97, respectively. In B-ALL patients, (CD10/CD19/CD34/CD45) + (CD10/CD19/CD34/CD97) represented the highest incidence of expression of leukemic cells markers with a significant correlation with blasts count, suggesting that these are more specific for MRD detection. Also FCM is relatively cost effective for detection of MRD in ALL patients and its applicability in routine leukemia lab is valuable. MRD evaluation at the end of the induction therapy (i.e. day 35 or 42 according to the different schedules) is advised. Also, Ig/T cell receptor gene rearrangements and gene fusions analyzed by polymerase chain reaction (PCR) are preferred.

Influence of Musculoskeletal Manifestations as the Only Presenting Symptom in B-Cell Acute Lymphoblastic Leukemia

OBJECTIVE

To evaluate the clinical and prognostic impact of musculoskeletal manifestations as the only initial presenting symptom in childhood acute lymphoblastic leukemia (ALL).

STUDY DESIGN

We retrospectively reviewed 158 children with precursor B-cell type ALL who were followed up for >2 years. The patients were assigned to the groups musculoskeletal manifestations (n = 24) or nonmusculoskeletal manifestations (n = 134) based on initial presenting symptom. The symptom duration (regarding any initial presenting symptom) and the leukemic symptom duration (regarding symptoms of systemic manifestation, such as fever, bleeding, or pallor) were assessed, along with other clinical characteristics.

RESULTS

The musculoskeletal manifestations group exhibited a longer symptom duration than the nonmusculoskeletal manifestations group (43 days vs 22 days, P = .006), but overall survival did not significantly differ between the groups. Multivariate analysis indicated that a longer symptom duration did not affect prognosis but that a longer leukemic symptom duration was associated with a poorer prognosis (hazard ratio, 7.720; P = .048).

CONCLUSION

Musculoskeletal manifestations are associated significantly with diagnostic delay, but this delay does not affect the prognosis. Diagnostic delay after the onset of leukemic symptoms, however, does appear to affect the prognosis. Intensive evaluations for hematologic malignancies may be unnecessary in children who complain of limb pain without any definite cause, unless they also present with accompanying leukemic symptoms.

The effect of central nervous system involvement and irradiation in childhood acute lymphoblastic leukemia: Lessons from the NOPHO ALL-92 and ALL-2000 protocols

BACKGROUND

Central nervous system irradiation (CNS-RT) has played a central role in the cure of acute lymphoblastic leukemia (ALL), but due to the risk of long-term toxicity, it is now considered a less-favorable method of CNS-directed therapy.

PROCEDURES

Retrospectively, we estimated the effect of CNS involvement and CNS-RT on events and overall survival (OS) in 835 children treated for high-risk ALL in the Nordic Society of Paediatric Haematology and Oncology (NOPHO) ALL-92 and ALL-2000 trials.

RESULTS

We did not observe a statistically significant difference in the OS or event-free survival (EFS) in patients with CNS involvement at diagnosis, but the risk of isolated CNS relapse was higher (hazard ratio [HR] 7.09, P < 0.001). CNS-RT was given to 169 of the 783 patients in first complete remission, of which 16 had CNS involvement at diagnosis. In general, CNS-RT improved EFS (HR 0.58, P < 0.05) but not OS (HR 0.69, P = n.s.). The adjusted HRs for all relapses, isolated bone marrow relapse, CNS-involving relapse, and isolated CNS relapse, were 0.47 (P < 0.01), 0.50 (P < 0.05), 0.34 (P < 0.01), and 0.12 (P < 0.01), respectively, in irradiated patients.

CONCLUSIONS

CNS-RT was associated with an advantage in EFS by decreasing the risk of relapse but without improving OS.

Immunophenotypic Modulation of the Blast Cells in Childhood Acute Lymphoblastic Leukemia Minimal Residual Disease Detection

Early clearance of leukemic cells during induction therapy of childhood acute lymphoblastic leukemia (ALL) is a basis for treatment optimization. Currently, the most widely used methods for the detection of minute residual malignant cells in the bone marrow and/or peripheral blood, minimal residual disease (MRD), are PCR and flow cytometry (FCM). Immunophenotypic modulation (IM) is a well known factor that can hamper the accurate FCM analysis.

AIM

To report the IM detected by 8-color FCM during the BFM-type remission induction in 24 consecutive MRD-positive samples of children with B-cell precursor ALL and the possible implications for MRD detection.

PATIENTS AND METHODS

Between 2010 and 2012 we prospectively followed up the MRD on days 15 and 33 of induction treatment in bone marrow (BM) samples and on day 8 in peripheral blood (PB). The IM was assessed by comparative analyses of the changes in the mean fluorescence intensity of 7 highly relevant antigens expressed by the leukemic cells and normal B-lymphocytes.

RESULTS

IM occurred, to different extents, in all analyzed day 15 BM and in most day 33 BM samples. Statistically significant changes in the MFI-levels of four CDs expressed by the leukemic blasts were observed: downmodulation of CD10, CD19 and CD34 and upmodulation of CD20. No changes in the expression of CD38, CD58 and CD45 were noticed.

CONCLUSIONS

Measuring the MRD by standardized 8-color flow cytometry helps improve the monitoring of the disease, leading to better therapeutic results. However, the IM of the different antigens expressed by the leukemic blasts should be taken into consideration and cautiously analyzed.

Clinical impact of minimal residual disease in children with different subtypes of acute lymphoblastic leukemia treated with Response-Adapted therapy

To determine the clinical significance of minimal residual disease (MRD) in patients with prognostically relevant subtypes of childhood acute lymphoblastic leukemia (ALL), we analyzed data from 488 patients treated in St Jude Total Therapy Study XV with treatment intensity based mainly on MRD levels measured during remission induction. MRD levels on day 19 predicted treatment outcome for patients with hyperdiploid >50 ALL, National Cancer Institute (NCI) standard-risk B-ALL or T-cell ALL, while MRD levels on day 46 were prognostic for patients with NCI standard-risk or high-risk B-ALL. Patients with t(12;21)/(ETV6-RUNX1) or hyperdiploidy >50 ALL had the best prognosis; those with a negative MRD on day 19 had a particularly low risk of relapse: 1.9% and 3.8%, respectively. Patients with NCI high-risk B-ALL or T-cell ALL had an inferior outcome; even with undetectable MRD on day 46, cumulative risk of relapse was 12.7% and 15.5%, respectively. Among patients with NCI standard-risk B-ALL, the outcome was intermediate overall but was poor if MRD was ⩾1% on day 19 or MRD was detectable at any level on day 46. Our results indicate that the clinical impact of MRD on treatment outcome in childhood ALL varies considerably according to leukemia subtype and time of measurement.

Prognostic significance of day 14 bone marrow evaluation in adults with Philadelphia chromosome-negative acute lymphoblastic leukemia

BACKGROUND

The role of day 14 (D14) bone marrow (BM) assessment in detecting increased blasts in patients undergoing induction for acute lymphoblastic leukemia (ALL) is not well defined.

METHODS

This study evaluated 389 adolescent and adult patients with previously untreated Philadelphia chromosome-negative ALL who received frontline induction chemotherapy and for whom a D14 BM assessment was performed.

RESULTS

A D14 BM blast proportion < 10% (including blast-free aplastic BM) was observed in 319 patients (82%), 10% to 29% was observed in 31 patients (8%), and ≥30% was observed in 39 patients (10%). The composite complete remission (CR)/complete remission with inadequate platelet recovery (CRp) rates for these groups were 99.7%, 87%, and 79%, respectively. The median event-free survival (EFS) was 49, 33, and 9 months, respectively (P < .001). The median overall survival (OS) was 88, 37, and 21 months, respectively (P < .001). The D14 BM blast group was the only factor predictive for the achievement of CR/CRp (P < .001). According to a multivariate analysis, the D14 BM blast group was independently prognostic for both EFS (hazard ratio [HR], 1.44; 95% confidence interval [CI], 1.12-1.85; P = .004) and OS (HR, 1.45; 95% CI, 1.14-1.85; P = .003). However, when minimal residual disease (MRD) assessment at the time of CR was added to the model, the D14 BM blast group was no longer prognostic for EFS or OS.

CONCLUSIONS

An assessment of residual D14 BM blasts in patients with ALL is highly predictive of the achievement of CR with induction chemotherapy and of EFS and OS. However, the D14 BM blast assessment is less prognostic of long-term outcomes when an MRD assessment is also available. Cancer 2016;122:3812-3820. © 2016 American Cancer Society.

Advanced lymphoblastic clones detection in T-cell leukemia

T cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignant neoplasm of the lymphocyte precursors that suffered malignant transformation arresting the lymphoid cell differentiation. Clinical studies revealed monoor, more rarely, oligoclonal nature of the disease. A precise identification of malignant clone markers is both the crucial stage of early diagnostics and the essential prognostic factor for therapeutic treatment. Here we present an improved system for unbiased detection of lymphoblastic clones in bone marrow aspirates of T-ALL patients. The system based on multiplex PCR of rearranged T-cell receptor locus (TRB) and straightforward sequencing of the resulted PCR fragments. Testing of the system on genomic DNA from Jurkat cell line and four clinical bone marrow aspirates revealed a set of unique TRB rearrangements that precisely characterize each of tested samples. Therefore, the outcome of the system produces highly informative molecular genetic markers for further monitoring of minimal residual disease in T-ALL patients.

Accurate Sample Assignment in a Multiplexed, Ultrasensitive, High-Throughput Sequencing Assay for Minimal Residual Disease

High-throughput sequencing (HTS) (next-generation sequencing) of the rearranged Ig and T-cell receptor genes promises to be less expensive and more sensitive than current methods of monitoring minimal residual disease (MRD) in patients with acute lymphoblastic leukemia. However, the adoption of new approaches by clinical laboratories requires careful evaluation of all potential sources of error and the development of strategies to ensure the highest accuracy. Timely and efficient clinical use of HTS platforms will depend on combining multiple samples (multiplexing) in each sequencing run. Here we examine the Ig heavy-chain gene HTS on the Illumina MiSeq platform for MRD. We identify errors associated with multiplexing that could potentially impact the accuracy of MRD analysis. We optimize a strategy that combines high-purity, sequence-optimized oligonucleotides, dual indexing, and an error-aware demultiplexing approach to minimize errors and maximize sensitivity. We present a probability-based, demultiplexing pipeline Error-Aware Demultiplexer that is suitable for all MiSeq strategies and accurately assigns samples to the correct identifier without excessive loss of data. Finally, using controls quantified by digital PCR, we show that HTS-MRD can accurately detect as few as 1 in 10(6) copies of specific leukemic MRD.

Excellent outcome of minimal residual disease-defined low-risk patients is sustained with more than 10 years follow-up: results of UK paediatric acute lymphoblastic leukaemia trials 1997-2003

BACKGROUND

Minimal residual disease (MRD) is defined as the presence of sub-microscopic levels of leukaemia. Measurement of MRD from bone marrow at the end of induction chemotherapy (day 28) for childhood acute lymphoblastic leukaemia (ALL) can highlight a large group of patients (>40%) with an excellent (>90%) short-term event-free survival (EFS). However, follow-up in recent published trials is relatively short, raising concerns about using this result to infer the safety of further therapy reduction in the future.

METHODS

We examined MRD data on 225 patients treated on one of three UKALL trials between 1997 and 2003 to assess the long-term (>10 years follow-up) outcome of those patients who had low-risk MRD (<0.01%) at day 28.

RESULTS

Our pilot data define a cohort of 53% of children with MRD <0.01% at day 28 who have an EFS of 91% and long-term overall survival of 97%. Of 120 patients with day-28 MRD <0.01% and extended follow-up, there was one death due to treatment-related toxicity, one infectious death while in complete remission, and four relapse deaths.

CONCLUSIONS

The excellent outcome for childhood ALL in patients with MRD <0.01% after induction chemotherapy is sustained for more than 10 years from diagnosis. This supports the potential exploration of further reduction of therapy in this group, in an attempt to reduce treatment-related mortality and late effects.

Current Strategies for the Detection of Minimal Residual Disease in Childhood Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is the most common cancer in children. Current treatment strategies for childhood ALL result in long-term remission for approximately 90% of patients. However, the therapeutic response is worse among those who relapse. Several risk stratification approaches based on clinical and biological aspects have been proposed to intensify treatment in patients with high risk of relapse and reduce toxicity on those with a greater probability of cure.

The detection of residual leukemic cells (minimal residual disease, MRD) is the most important prognostic factor to identify high-risk patients, allowing redefinition of chemotherapy. In the last decades, several standardized research protocols evaluated MRD using immunophenotyping by flow cytometry and/or real-time quantitative polymerase chain reaction at different time points during treatment. Both methods are highly sensitive (10⁻³ a 10⁻⁵), but expensive, complex, and, because of that, require qualified staff and frequently are restricted to reference centers.

The aim of this article was to review technical aspects of immunophenotyping by flow cytometry and real-time quantitative polymerase chain reaction to evaluate MRD in ALL.

Stanniocalcin1 gene expression in patients with acute leukemia: impact on response to therapy and disease outcome

INTRODUCTION

Stanniocalcin1 (STC1) is a hormone that regulates cell growth and survival; this study aimed to evaluate the STC1 gene expression in patients with acute leukemia and assess its prognostic significance.

METHODS

Seventy-six patients with acute leukemia were enrolled for determination of mRNA STC1 by real-time quantitative polymerase chain reaction at diagnosis and at day 28.

RESULTS

Median STC1 gene expression was 16.2 and 4.43 in patients with acute myeloid leukemia and 9.67 and 2.37 in patients with acute lymphoblastic leukemia on days 0 and 28, respectively. A cutoff level for STC1 gene expression was established subdividing patients into high- and low-STC1 gene expression groups. Median STC1 gene expression at days 0 and 28 was significantly higher among patients who were nonresponders to therapy than among those who were therapy responders in both groups. Patients achieving complete remission had significantly lower baseline STC1 gene expression than those in relapse. High STC1 gene expression was associated with shorter overall and disease-free survival times.

CONCLUSION

STC1 gene expression at diagnosis might be a useful prognostic marker for clinical outcome and monitoring therapeutic response in patients with acute leukemia.

Major impact of an early bone marrow checkpoint (day 21) for minimal residual disease in flow cytometry in childhood acute lymphoblastic leukemia

The early persistence of minimal residual disease (MRD) is considered a poor prognostic factor indicative of chemoresistance in acute lymphoblastic leukemia. In French children, chemosensitivity is assessed at day 21 post-induction by cytomorphology. Here, it was investigated whether a more precise evaluation could be obtained at this time point with multiparameter flow cytometry (MFC). This study enrolled 123 children with de novo acute lymphoblastic leukemia. MRD0 was investigated at day 21 in MFC with a combination of antibodies based on the immunophenotype of diagnosis. It was also evaluated at day 35 by immunoglobulin/T-cell receptor quantitative real-time polymerase chain reaction (MRD1). Three risk groups could be delineated based on MRD0. Patients with MFC/MRD0 levels >10^-2 (n = 25) were considered high risk, those with levels between 10^-2 and 10^-4 (n = 46) intermediate risk, and those <10^-4 (n = 50) low risk. Overall survival (p = 0.048) and event-free survival (EFS, p = 0.00017) were significantly different between these three groups. EFS of the 14 corticoresistant patients strongly depended on their MRD0 level (p = 0.004). Similarly, both EFS (p = 0.0004) and overall survival (p = 0.02) were significantly different in the 109 chemosensitive patients, according to MRD0 levels. MRD0 and MRD1 levels, compared with 112 patients, were consistent (-/- or +/+) in 57.2% of the cases. Both MRD0+/MRD1+ and MRD0+/MRD1- patients had a significantly worse EFS (p = 0.0001) than those with undetectable MRD at both MRD0 and MRD1. This study confirms the usefulness and superiority of an early point of MRD detection by MFC. In addition, MRD0 in MFC identifies a subgroup of patients with poorer prognosis (MRD0+/MRD1-). Copyright © 2015 John Wiley & Sons, Ltd.

Proposal for the standardization of flow cytometry protocols to detect minimal residual disease in acute lymphoblastic leukemia

Minimal residual disease is the most powerful predictor of outcome in acute leukemia and is useful in therapeutic stratification for acute lymphoblastic leukemia protocols. Nowadays, the most reliable methods for studying minimal residual disease in acute lymphoblastic leukemia are multiparametric flow cytometry and polymerase chain reaction. Both provide similar results at a minimal residual disease level of 0.01% of normal cells, that is, detection of one leukemic cell in up to 10,000 normal nucleated cells. Currently, therapeutic protocols establish the minimal residual disease threshold value at the most informative time points according to the appropriate methodology employed. The expertise of the laboratory in a cancer center or a cooperative group could be the most important factor in determining which method should be used. In Brazil, multiparametric flow cytometry laboratories are available in most leukemia treatment centers, but multiparametric flow cytometry processes must be standardized for minimal residual disease investigations in order to offer reliable and reproducible results that ensure quality in the clinical application of the method. The Minimal Residual Disease Working Group of the Brazilian Society of Bone Marrow Transplantation (SBTMO) was created with that aim. This paper presents recommendations for the detection of minimal residual disease in acute lymphoblastic leukemia based on the literature and expertise of the laboratories who participated in this consensus, including pre-analytical and analytical methods. This paper also recommends that both multiparametric flow cytometry and polymerase chain reaction are complementary methods, and so more laboratories with expertise in immunoglobulin/T cell receptor (Ig/TCR) gene assays are necessary in Brazil.

Minimal residual disease analysis by eight-color flow cytometry in relapsed childhood acute lymphoblastic leukemia

Multiparametric flow cytometry is an alternative approach to the polymerase chain reaction method for evaluating minimal residual disease in treatment protocols for primary acute lymphoblastic leukemia. Given considerable differences between primary and relapsed acute lymphoblastic leukemia treatment regimens, flow cytometric assessment of minimal residual disease in relapsed leukemia requires an independent comprehensive investigation. In the present study we addressed evaluation of minimal residual disease by flow cytometry in the clinical trial for childhood relapsed acute lymphoblastic leukemia using eight-color flow cytometry. The major challenge of the study was to reliably identify low amounts of residual leukemic cells against the complex background of regeneration, characteristic of follow-up samples during relapse treatment. In a prospective study of 263 follow-up bone marrow samples from 122 patients with B-cell precursor acute lymphoblastic leukemia, we tested various B-cell markers, adapted the antibody panel to the treatment protocol, and evaluated its performance by a blinded parallel comparison with the polymerase chain reaction data. The resulting eight-color single-tube panel showed a consistently high overall concordance (P<0.001) and, under optimal conditions, sensitivity similar to that of the reference polymerase chain reaction method. Overall, evaluation of minimal residual disease by flow cytometry can be successfully integrated into the clinical management of relapsed childhood acute lymphoblastic leukemia either as complementary to the polymerase chain reaction or as an independent risk stratification tool. ALL-REZ BFM 2002 clinical trial information: NCT00114348.

Clinical utility of sequential minimal residual disease measurements in the context of risk-based therapy in childhood acute lymphoblastic leukaemia: a prospective study

BACKGROUND

The level of minimal residual disease during remission induction is the most important prognostic indicator in patients with acute lymphoblastic leukaemia (ALL). We aimed to establish the clinical significance of minimal residual disease in a prospective trial that used sequential minimal residual disease measurements to guide treatment decisions.

METHODS

Between June 7, 2000, and Oct 24, 2007, 498 assessable patients with newly diagnosed ALL were enrolled in a clinical trial at St Jude Children's Research Hospital. We provisionally classified the risk of relapse as low, standard, or high according to patients' baseline clinical and laboratory features. Final risk assignment to establish treatment intensity was based mainly on minimal residual disease levels measured on days 19 and 46 of remission induction, and on week 7 of maintenance treatment. Additional measurements of minimal residual disease were made on weeks 17, 48, and 120 (end of treatment). The primary aim was to establish the association between event-free survival and patients' minimal residual disease levels during remission induction and sequentially post-remission. This trial was registered at ClinicalTrials.gov, number NCT00137111.

FINDINGS

Irrespective of the provisional risk classification, 10-year event-free survival was significantly worse for patients with 1% or greater minimal residual disease levels on day 19 compared with patients with lower minimal residual disease levels (69·2%, 95% CI 49·6-82·4, n=36 vs 95·5%, 91·7-97·5, n=244; p<0·001 for the provisional low-risk group and 65·1%, 50·7-76·2, n=56 vs 82·9%, 75·6-88·2, n=142; p=0·01 for the provisional standard-risk group). 12 patients with provisional low-risk ALL and 1% or higher minimal residual disease levels on day 19 but negative minimal residual disease (<0·01%) on day 46 were treated for standard-risk ALL and had a 10-year event-free survival of 88·9% (43·3-98·4). For the 280 provisional low-risk patients, a minimal residual disease level of less than 1% on day 19 predicted a better outcome, irrespective of the minimal residual disease level on day 46. Of provisional standard-risk patients with minimal residual disease of less than 1% on day 19, the 15 with persistent minimal residual disease on day 46 seemed to have an inferior 10-year event-free survival compared with the 126 with negative minimal residual disease (72·7%, 42·5-88·8 vs 84·0%, 76·3-89·4; p=0·06) after receiving the same post-remission treatment for standard-risk ALL. Of patients attaining negative minimal residual disease status after remission induction, minimal residual disease re-emerged in four of 382 studied on week 7, one of 448 at week 17, and one of 437 at week 48; all but one of these six patients died despite additional treatment. By contrast, relapse occurred in only two of the 11 patients who had decreasing minimal residual disease levels between the end of induction and week 7 of maintenance therapy and were treated with chemotherapy alone.

INTERPRETATION

Minimal residual disease levels during remission induction treatment have important prognostic and therapeutic implications even in the context of minimal residual disease-guided treatment. Sequential minimal residual disease monitoring after remission induction is warranted for patients with detectable minimal residual disease.

FUNDING

National Institutes of Health and American Lebanese Syrian Associated Charities.

Genomics in acute lymphoblastic leukaemia: insights and treatment implications

Acute lymphoblastic leukaemia (ALL) is the commonest childhood cancer and an important cause of morbidity from haematological malignancies in adults. In the past several years, we have witnessed major advances in the understanding of the genetic basis of ALL. Genome-wide profiling studies, including microarray analysis and genome sequencing, have helped identify multiple key cellular pathways that are frequently mutated in ALL such as lymphoid development, tumour suppression, cytokine receptors, kinase and Ras signalling, and chromatin remodeling. These studies have characterized new subtypes of ALL, notably Philadelphia chromosome-like ALL, which is a high-risk subtype characterized by a diverse range of alterations that activate cytokine receptors or tyrosine kinases amenable to inhibition with approved tyrosine kinase inhibitors. Genomic profiling has also enabled the identification of inherited genetic variants of ALL that influence the risk of leukaemia development, and characterization of the relationship between genetic variants, clonal heterogeneity and the risk of relapse. Many of these findings are of direct clinical relevance and ongoing studies implementing clinical sequencing in leukaemia diagnosis and management have great potential to improve the outcome of patients with high-risk ALL.

Bone marrow minimal residual disease was an early response marker and a consistent independent predictor of survival after anti-GD2 immunotherapy

PURPOSE

Immunotherapy is a standard of care for children with high-risk neuroblastoma, where bone marrow (BM) is the predominant metastatic site. Early response markers of minimal residual disease (MRD) in the BM that are also predictive of survival could help individualize patient therapies.

PATIENTS AND METHODS

After achieving first remission (n = 163), primary refractory disease (n = 102), or second remission (n = 95), children with stage 4 neuroblastoma received anti-GD2 3F8 antibody immunotherapy. BM MRD before 3F8 treatment and after cycle 2 (postMRD) was measured using a four-marker panel (B4GALNT1, PHOX2B, CCND1, and ISL1) by quantitative reverse transcription polymerase chain reaction. Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method. Prognostic variables were tested in both univariable and multivariable analyses, and MRD markers were further assessed individually and in combination as binary composite (postMRD: 0 and 1) and as equal sum (postMRDSum: 0 to 4) using the Cox regression models, and their predictive accuracy was determined by the concordance index.

RESULTS

When BM was evaluated after cycle 2, individual markers were highly predictive of PFS and OS. The prediction accuracy improved when they were combined in postMRDSum. A multivariable model taking into account all the variables significant in the univariable analyses identified postMRDSum to be independently predictive of PFS and OS. When the model for OS also included missing killer immunoglobulin-like receptor ligand, human antimouse antibody response, and the enrollment disease status, the concordance index was 0.704.

CONCLUSION

BM MRD after two cycles of immunotherapy was confirmed as an early response marker and a consistent independent predictor of survival.

Detection and management of minimal residual disease in acute lymphoblastic leukemia

The detection of minimal residual disease (MRD) has become part of the state-of-the-art diagnostics to guide treatment both in pediatric and adult acute lymphoblastic leukemia (ALL). This applies to the treatment of de novo and recurrent ALL. In high-risk ALL, MRD detection is considered an important tool to adjust therapy before and after hematopoietic stem cell transplantation. Precise quantification and quality control is instrumental to avoid false treatment assignment. A new methodological approach to analyzing MRD has become available and is based on next-generation sequencing. In principle, this technique will be able to detect a large number of leukemic subclones at a much higher speed than before. Carefully designed prospective studies need to demonstrate concordance or even superiority compared with those techniques in use right now: detection of aberrant expression of leukemia-specific antigens by flow cytometry of blood or bone marrow, or detection of specific rearrangements of the T-cell receptor or immunoglobulin genes by real-time quantitative polymerase chain reaction using DNA of leukemic cells. In some cases with known fusion genes, such as BCR/ABL, reverse transcriptase-polymerase chain reaction has been used as additional method to identify leukemic cells by analyzing RNA in patient samples. MRD detection may be used to modulate treatment intensity once it has been demonstrated at well-defined informative checkpoints that certain levels of MRD can reliably predict the risk of relapse. In addition, MRD is used as end point to determine the activity of a given agent or treatment protocol. If activity translates into antileukemic efficacy, MRD may be considered a surrogate clinical end point.

Risk factors for relapse in childhood acute lymphoblastic leukemia: prediction and prevention

With current treatment regimens, survival rates for acute lymphoblastic leukemia (ALL) have improved dramatically since the 1980s, with current 5-year overall survival rates estimated at greater than 85%. This success was achieved, in part, through the implementation of risk-stratified therapy. Nevertheless, for a subgroup of patients (15-20%) with newly diagnosed ALL who will ultimately relapse, traditional risk assessment remains inadequate. The risk of relapse may be estimated on the basis of diagnostic features or early treatment response findings. Further progress in this field may thus come from refinement of predictive factors for relapse and treatment adaptation and from the identification of biological subsets of ALL patients who could benefit from specific target therapies. This article summarizes the aspects associated with the identification of predictive factors for relapse in childhood ALL and options available for prevention of disease recurrence.

Methodological aspects of minimal residual disease assessment by flow cytometry in acute lymphoblastic leukemia: A French multicenter study

BACKGROUND

Minimal residual disease (MRD) assessment provides a powerful prognostic factor for therapeutic stratification in acute lymphoblastic leukemia (ALL). Multiparameter flow cytometry (MFC) has the potential for a rapid and sensitive identification of high risk patients. Our group has previously published that MRD levels analyzed by clone specific Ig/TcR-QPCR and MFC were concordant at a sensitivity of 10(-4) . Here we report the MFC methodological aspects from this multi-center experience.

METHODS

MRD was assessed by MFC in 1030 follow-up samples from 265 pediatric and adult patients with de novo ALL treated in the FRALLE, EORTC, or GRALL clinical trials. MRD assessment as applied by the eight participating MFC laboratories is described in detail regarding cell preparation, leukemia-associated immunophenotype (LAIP) markers and data analysis. Samples were obtained from bone marrow (BM) and peripheral blood (PB). Immunostaining was performed after erythrocyte lysis or Ficoll enrichment.

RESULTS

This study confirms the applicability of MFC-based MRD assessment in 97% of patients with ALL at the 10(-4) cut-off. MRD values after Ficoll enrichment and erythrocyte lysis were found comparable. Higher MRD values were obtained in BM than in PB, especially for B-lineage ALL.

CONCLUSIONS

Measurement of MRD by MFC at the 10(-4) cut-off is applicable within a few hours for almost all patients and using a comparable analytical strategy allows for multicenter collaborative studies. The method can be introduced in a strategy aimed at defining the risk of failure of patients with childhood or adult ALL.

High-throughput screening of human leukemia xenografts to identify dexamethasone sensitizers

Acute lymphoblastic leukemia (ALL) is the most common pediatric malignancy. Glucocorticoids (e.g., dexamethasone) form a critical component of chemotherapy regimens for pediatric ALL, and the initial response to glucocorticoid therapy is a major prognostic factor, where resistance is predictive of poor outcome. We have previously established a clinically relevant ALL xenograft model, consisting of primary pediatric ALL biopsies engrafted into immune-deficient mice, in which in vitro and in vivo dexamethasone sensitivity significantly correlated with patient outcome. In this study, we used high-throughput screening (HTS) to identify novel compounds that reverse dexamethasone resistance in a xenograft (ALL-19) derived from a chemoresistant pediatric ALL patient that is representative of the most common pediatric ALL subtype (B-cell precursor [BCP-ALL]). The compound 2-(4-chlorophenoxy)-2-methyl-N-(2-(piperidin-1-yl)phenyl)propanamide showed little cytotoxic activity alone (IC50 = 31 µM), but when combined with dexamethasone, it caused a marked decrease in cell viability. Fixed-ratio combination assays were performed against a broad panel of dexamethasone-resistant and -sensitive xenografts representative of BCP-ALL, T-cell ALL, and Mixed Lineage Leukemia-rearranged ALL, and synergy was observed in six of seven xenografts. We describe here the development of a novel 384-well cell-based high-throughput screening assay for identifying potential dexamethasone sensitizers using a clinically relevant ALL xenograft model.