Clinical significance of minimal residual disease in childhood acute lymphoblastic leukemia after first relapse

New markers for minimal residual disease detection in acute lymphoblastic leukemia

To identify new markers for minimal residual disease (MRD) detection in acute lymphoblastic leukemia (ALL), we compared genome-wide gene expression of lymphoblasts from 270 patients with newly diagnosed childhood ALL to that of normal CD19⁺CD10⁺ B-cell progenitors (n = 4). Expression of 30 genes differentially expressed by ≥ 3-fold in at least 25% of cases of ALL (or 40% of ALL subtypes) was tested by flow cytometry in 200 B-lineage ALL and 61 nonleukemic BM samples, including samples containing hematogones. Of the 30 markers, 22 (CD44, BCL2, HSPB1, CD73, CD24, CD123, CD72, CD86, CD200, CD79b, CD164, CD304, CD97, CD102, CD99, CD300a, CD130, PBX1, CTNNA1, ITGB7, CD69, CD49f) were differentially expressed in up to 81.4% of ALL cases; expression of some markers was associated with the presence of genetic abnormalities. Results of MRD detection by flow cytometry with these markers correlated well with those of molecular testing (52 follow-up samples from 18 patients); sequential studies during treatment and diagnosis-relapse comparisons documented their stability. When incorporated in 6-marker combinations, the new markers afforded the detection of 1 leukemic cell among 10(5) BM cells. These new markers should allow MRD studies in all B-lineage ALL patients, and substantially improve their sensitivity.

Relapse of acute lymphoblastic leukemia in children in the context of microarray analyses

Over the last four decades the treatment of patients with newly diagnosed childhood acute lymphoblastic leukemia (ALL) has improved remarkably. However, still about 20% of children with ALL relapse despite risk-adapted polychemotherapy. The prognosis of relapsed ALL is relatively poor, even with modern aggressive chemotherapy. Identification of the biological and genetic mechanisms contributing to recurrence in patients with ALL is critical for the development of effective therapeutic strategies to treat refractory leukemic patients. Allogeneic hematopoietic stem-cell transplantation is the treatment of choice for many children with relapsed ALL. The gene expression profile obtained by microarray technology could provide important determinants of the drug response and clinical outcome in childhood ALL. Incorporation of the data on expression levels of newly identified genes into existing strategies of risk stratification might improve clinical management. Current microarray data show correlation of in vitro drug resistance with significant patterns of gene expression and explain clinical differences between early and late relapse. Genes involved in cell proliferation, self-renewal and differentiation, protein biosynthesis, carbohydrate metabolism, and DNA replication and repair are usually among those highly expressed in relapsed lymphoblasts. Current status and future perspectives of microarray data on gene expression and drug resistance profile in relapsed pediatric ALL are discussed in this review.

[Minimal residual disease detection in acute leukemia patients by flow cytometric assay of cross-lineage antigen expression]

BACKGROUND

It has been demonstrated that flow cytometric detection of minimal residual disease (MRD) has a prognostic significance in the treatment of patients with acute leukemia. We investigated the significance of flow cytometric MRD detection for the first time in Korea.

METHODS

We analyzed the results of MRD detection in morphologically complete remission bone marrow aspirates from 89 patients with newly-diagnosed or relapsed acute leukemia, in which leukemic cells had cross-lineage antigen expression. Patients were grouped based on MRD frequencies: ≥ 1.0%, high MRD; <1.0%, low MRD.

RESULTS

Forty-seven ALL patients consisted of 10 with high and 37 with low MRD levels. Patients with high MRD levels showed a tendency of more frequent relapse than those with low MRD levels (40.0% and 13.5%, respectively) (P=0.08). High MRD group showed a tendency of short relapse-free survival (RFS) and overall survival (OS), although the differences were not statistically significant. Forty-two AML patients consisted of 16 with high and 26 with low MRD levels. There were no correlations between the MRD levels and relapse rate, RFS or OS. AML patients with high MRD levels showed significantly higher rate of unfavorable cytogenetic risk categories and lower rate of favorable risk categories (P=0.03).

CONCLUSIONS

MRD detection by flow cytometric assay of cross-lineage antigen expression would be useful in predicting treatment outcome in patients with ALL rather than AML. We expect that the establishment of the standardization of methods, time to test or antibody combination would be achieved through further trials in this country.

Immunologic minimal residual disease detection in acute lymphoblastic leukemia: a comparative approach to molecular testing

The generation of antisera directed against leukocyte differentiation antigens opened the possibility of studying minimal residual disease (MRD) in patients with acute lymphoblastic leukemia (ALL). During the three decades that followed the pioneering studies in this field, great progress has been made in the development of a wide array of monoclonal antibodies and of flow cytometric techniques for rare event detection. This advance was accompanied by an increasingly greater understanding of the immunophenotypic features of leukemic and normal lymphoid cells, and of the antigenic differences that make MRD studies possible. In parallel, molecular methods for MRD detection were established. The systematic application of immunologic and molecular techniques to study MRD in clinical samples has demonstrated the clinical significance of MRD in patients, leading to the use of MRD to regulate treatment intensity in many contemporary protocols. In this article, we discuss methodologic issues related to the immunologic monitoring of MRD and the evidence supporting its clinical significance, and compare the advantages and limitations of this approach to those of molecular monitoring of MRD.

Progress of minimal residual disease studies in childhood acute leukemia

Submorphologic (ie, minimal) residual disease (MRD) can be monitored in virtually all children and adolescents with acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL) using methods such as flow cytometric detection of leukemic immunophenotypes or polymerase chain reaction amplification of fusion transcripts, gene mutations, and clonal rearrangements of antigen-receptor genes. Numerous studies have demonstrated the clinical importance of measuring MRD, spurring the design of clinical trials in which MRD is used for risk assignment and treatment selection. Emerging results from these trials suggest that the adverse prognostic impact of low levels of MRD during the early phases of therapy can be diminished by treatment intensification. This article discusses the methods used for detecting MRD in childhood AML and ALL, the data obtained in studies correlating MRD with treatment outcome, the results of the initial trials using MRD, and the practical aspects related to the design of MRD-based clinical studies.

High-risk childhood acute lymphoblastic leukemia

Although most children with acute lymphoblastic leukemia (ALL) are cured, certain subsets have a high risk of relapse. Relapse risk can be predicted by early response to therapy, clinical and pharmacogenetic features of the host, and genetic characteristics of leukemic cells. Though early treatment response can be assessed by the peripheral blast cell count after 1 week of single-agent glucocorticoid treatment or percent of bone marrow blasts by morphology after 1 or 2 weeks of multiagent induction treatment, determination of minimal residual disease by polymerase chain reaction (PCR) or flow cytometry after 2 to 6 weeks of induction is the most precise and useful measure. Augmented therapy has improved outcome for the poor responders to initial treatment. Infants with mixed-lineage leukemia (MLL)-rearranged ALL comprise a very poor-risk group wherein further intensification of chemotherapy causes significant toxicity. Hybrid protocols incorporating drugs effective for acute myeloid leukemia could improve survival, a strategy being tested in international trials. Studies on the biology of MLL-induced leukemogenesis have prompted the development of novel targeted agents, currently under evaluation in clinical trials. Short-term outcomes of patients with Philadelphia chromosome (Ph)-positive ALL have improved significantly by adding tyrosine kinase inhibitors to standard chemotherapy regimens. New agents and methods to overcome resistance are under investigation, and allogeneic stem cell transplantation is recommended for certain subsets of patients, for example those with Ph+ and T-cell ALL with poor early response. Genome-wide interrogation of leukemic cell genetic abnormalities and germline genetic variations promise to identify new molecular targets for therapy.

Role of minimal residual disease monitoring in adult and pediatric acute lymphoblastic leukemia

Assays that measure minimal residual disease (MRD) can determine the response to treatment in patients with acute lymphoblastic leukemia (ALL) much more precisely than morphologic screening of bone marrow smears. The clinical significance of MRD, detected by flow cytometry or polymerase chain reaction-based methods in childhood ALL, has been established. Hence, MRD is being used in several clinical trials to adjust treatment intensity. Similar findings have been gathered in adult patients with ALL, making MRD one of the most powerful and informative parameters to guide clinical management. This article discusses practical issues related to MRD methodologies and the evidence supporting the use of MRD for risk assignment in clinical trials.

Establishment and validation of a standard protocol for the detection of minimal residual disease in B lineage childhood acute lymphoblastic leukemia by flow cytometry in a multi-center setting

Minimal residual disease detection, used for clinical management of children with acute lymphoblastic leukemia, can be performed by molecular analysis of antigen-receptor gene rearrangements or by flow cytometric analysis of aberrant immunophenotypes. For flow minimal residual disease to be incorporated into larger national and international trials, a quality assured, standardized method is needed which can be performed in a multi-center setting. We report a four color, flow cytometric protocol established and validated by the UK acute lymphoblastic leukemia Flow minimal residual disease group. Quality assurance testing gave high inter-laboratory agreement with no values differing from a median consensus value by more than one point on a logarithmic scale. Prospective screening of B-ALL patients (n=206) showed the method was applicable to 88.3% of patients. The minimal residual disease in bone marrow aspirates was quantified and compared to molecular data. The combined risk category concordance (minimal residual disease levels above or below 0.01%) was 86% (n=134). Thus, this standardized protocol is highly reproducible between laboratories, sensitive, applicable, and shows good concordance with molecular-based analysis.

Childhood acute lymphoblastic leukemia: update on prognostic factors

PURPOSE OF REVIEW

With current treatment regimens, event-free survival rates for childhood acute lymphoblastic leukemia (ALL) approach or exceed 80%. This success was achieved, in part, through the implementation of risk-stratified therapy. However, for the 15-20% of children with newly diagnosed ALL who will ultimately relapse, traditional risk assessment remains inadequate. This review highlights recent advances in our understanding of prognostic factors that may be used to refine risk group classification.

RECENT FINDINGS

An increasingly sophisticated understanding of genetic abnormalities in leukemia cells (including chromosomal abnormalities and patterns of gene expression), response to treatment, and host pharmacogenomics offers the potential to enhance or supplant currently applied prognostic criteria for use in treatment planning for childhood ALL.

SUMMARY

Identification of biologically distinctive subsets of ALL through cytogenetic, molecular, and gene expression studies, as well as investigations of minimal residual disease and host pharmacogenomics, offer promising avenues of research. Integration of molecular tools into clinical practice will ultimately allow for more precise risk stratification and individualized treatment planning.

Relapsed acute lymphoblastic leukemia: current status and future opportunities

Significant improvements in primary therapy for childhood acute lymphoblastic leukemia (ALL) have led to dramatic increases in cure rates over the past few decades. Relapsed ALL, however, remains more common than new diagnoses of many common pediatric malignancies. Outcomes for patients with relapsed ALL remain poor, especially for patients with early bone marrow relapse. However, most relapse patients do achieve a second complete remission, followed by therapeutic options including further chemotherapy and hematopoietic stem cell transplant. The level of minimal residual disease after achieving second remission or before transplant may predict outcomes. The substantial likelihood of achieving second remission with familiar drug combinations may discourage participation in formal relapse studies. The high likelihood of achieving a third remission may discourage participation in single-agent trials of new drugs, despite the critical need for novel agents with activity against resistant disease that may improve outcomes for recurrent ALL.

Minimal residual disease in acute lymphoblastic leukemia

In patients with acute lymphoblastic leukemia (ALL), monitoring of minimal residual disease (MRD) offers a way to precisely assess early treatment response and detect relapse. Established methods to study MRD are flow cytometric detection of abnormal immunophenotypes, polymerase chain reaction (PCR) amplification of antigen-receptor genes, and PCR amplification of fusion transcripts. The strong correlation between MRD levels and risk of relapse in childhood ALL is well demonstrated; studies in adult patients also support its prognostic value. Hence, results of MRD studies can be used to select treatment intensity and duration, and to estimate the optimal timing for hematopoietic stem cell transplantation. Practical issues in the implementation of MRD assays in clinical studies include determining the most informative time point to study MRD and the levels of MRD that will trigger changes in treatment intensity, as well as the relative cost and informative power of different methodologies. The identification of new markers of leukemia and the use of increasingly refined assays should further facilitate routine monitoring of MRD and help to clarify the cellular and biologic features of leukemic cells that resist chemotherapy in vivo.

Status of minimal residual disease testing in childhood haematological malignancies

In children with acute leukaemia, measurements of minimal residual disease (MRD) provide unique information on treatment response and have become a crucial component of contemporary treatment protocols. In acute lymphoblastic leukaemia (ALL), the most useful MRD assays are based on polymerase chain reaction (PCR) amplification of antigen-receptor genes, and on flow cytometric detection of abnormal immunophenotypes. The latter is the only MRD assay available for most patients with acute myeloid leukaemia (AML). PCR amplification of chromosomal breakpoints and fusion transcripts can also be used to track MRD in a minority of patients with ALL or AML. Because of the strong correlation between MRD levels and risk of relapse, several ongoing regimens include treatment intensification for children with higher MRD. Treatment de-intensification for patients with early MRD clearance is also being tested. In addition to their direct clinical application, MRD measurements can be used to better understand the molecular and cellular mechanisms of drug resistance in vivo. The identification of new markers of leukaemia and the use of increasingly sophisticated technologies for detection of rare cells should further facilitate routine monitoring of MRD and elucidate the features of drug-resistant leukaemic cells.

Bone-marrow relapse in paediatric acute lymphoblastic leukaemia

Marrow relapse is the major obstacle to cure for 10-15% of young patients with acute lymphoblastic leukaemia (ALL). Recent investigations into the biology of minimal residual disease indicate that many early relapses derive from residual cells present at first diagnosis, but some late relapses might represent new mutations in leukaemic cells not eliminated by conventional therapy. Treatment of marrow relapse involves higher doses and more intensive schedules of the drugs used for initial therapy with or without haemopoietic stem cell transplantation. In most reports, transplantation is better than continuation chemotherapy in early marrow relapse, but its role in later relapse is less clear. Current therapy cures 10% of patients with early marrow relapses and 50% of those with late relapses, but outcomes have changed little in the past two decades. Understanding the molecular biology of ALL underlies development of improved risk stratification and new therapies. Although better drugs are needed, introduction of new agents into clinical trials in paediatric disease has been difficult. Innovative trial designs and use of valid surrogate endpoints may expedite this process.

Reinduction platform for children with first marrow relapse of acute lymphoblastic Leukemia: A Children's Oncology Group Study[corrected]

PURPOSE

Treatment of childhood relapsed acute lymphoblastic leukemia (ALL) remains a significant challenge. The goal of the Children's Oncology Group (COG) AALL01P2 study was to develop a safe and active chemotherapy reinduction platform, which could be used to evaluate novel agents in future trials.

PATIENTS AND METHODS

One hundred twenty-four patients with ALL and first marrow relapse received three, 35-day blocks of reinduction chemotherapy: 69 with early relapse (ER; < 36 months from initial diagnosis) and 55 with late relapse (LR). Minimal residual disease (MRD) was measured by flow cytometry after each treatment block.

RESULTS

Second complete remission (CR2) rates at the end of block 1 in 117 assessable patients were 68% +/- 6% for ER (n = 63) and 96% +/- 3% for LR (n = 54; P < .0001). Five of seven patients with T-cell ALL (T-ALL) failed to achieve CR2. Among patients in CR2, MRD greater than 0.01% was detected at the end of block 1 in 75% +/- 7% of ER (n = 36) versus 51% +/- 8% of LR (n = 43; P = .0375) and 12-month event-free survival was 80% +/- 7% versus 58% +/- 7% in MRD-negative versus positive patients (P < .0005). Blocks 2 and 3 of therapy resulted in reduction of MRD burden in 40 of 56 patients who were MRD positive after block 1. Toxicity was acceptable during all three blocks with five deaths (4%) from infections.

CONCLUSION

The AALL01P2 regimen is a tolerable and active reinduction platform, suitable for testing in combination with novel agents in B-precursor ALL. Alternative strategies are needed for T-ALL. Serial MRD measurements were feasible and prognostic of outcome.

Chemoimmunotherapy reinduction with epratuzumab in children with acute lymphoblastic leukemia in marrow relapse: a Children's Oncology Group Pilot Study

PURPOSE

To determine the tolerability and serum concentration of epratuzumab, a humanized monoclonal antibody targeting CD22, administered alone and in combination with reinduction chemotherapy in children with relapsed acute lymphoblastic leukemia (ALL), and to preliminarily assess tumor targeting and efficacy.

PATIENTS AND METHODS

Therapy consisted of a single-agent phase (epratuzumab 360 mg/m(2)/dose intravenously twice weekly x four doses), followed by four weekly doses of epratuzumab in combination with standard reinduction chemotherapy. Morphologic and minimal residual disease (MRD) responses were determined at the end of this 6-week period. Serum concentrations of epratuzumab were determined before and 30 minutes after infusions, and CD22 targeting efficiency was determined by quantifying changes in CD22 expression after epratuzumab administration.

RESULTS

Fifteen patients (12 fully assessable for toxicity) with first or later CD22-positive ALL marrow relapse enrolled on the feasibility portion of this study from December 2005 to June 2006. Two dose-limiting toxicities occurred: one grade 4 seizure of unclear etiology and one asymptomatic grade 3 ALT elevation. In all but one patient, surface CD22 was not detected by flow cytometry on peripheral blood leukemic blasts within 24 hours of drug administration, indicating effective targeting of leukemic cells by epratuzumab. Nine patients achieved a complete remission after chemoimmunotherapy, seven of whom were MRD negative.

CONCLUSION

Treatment with epratuzumab plus standard reinduction chemotherapy is feasible and acceptably tolerated in children with relapsed CD22-positive ALL. CD22 targeting was efficient, and the majority of patients achieved favorable early responses.

Indications and donor selections for allogeneic stem cell transplantation in children with hematologic malignancies

Allogeneic stem cell transplantation (SCT) is the only curative approach for many patients with advanced or high-risk leukemia. Advances in supportive care and management of graft-versus-host disease have resulted in improvements in outcomes of related and unrelated donor SCT, creating controversies as to which strategy might be the optimal therapy for individual patients. This article discusses the indications and donor selection strategies for SCT in patients with malignant hematologic disease.

Outcome After Relapse Among Children With Standard-Risk Acute Lymphoblastic Leukemia: Children's Oncology Group Study CCG-1952

Purpose

The event-free survival (EFS) of children with standard-risk acute lymphoblastic leukemia (SR-ALL) is now more than 80%. However, prognosis after relapse continues to be poor. We examined postrelapse outcomes of children initially treated on the Children's Cancer Group CCG-1952 study.

Patients and Methods

We evaluated outcomes after bone marrow (BM) relapse and isolated extramedullary (EM) relapse for 347 patients with SR-ALL (WBC < 50,000/μL; age, 1 to 9 years). The prognostic significance of several factors for EFS after relapse (EFS2) was assessed by Cox regression analysis. Stem-cell transplant (SCT) was compared with chemotherapy as salvage treatment.

Results

The mean ± SE times to isolated central nervous system relapse, BM relapse, and isolated testicular relapse were 23 ± 1 months (range, 1 to 88 months), 36 ± 1 months (range, 2 to 79 months), and 40 ± 2 months (range, 16 to 64 months), respectively. The estimated percent ± SE 3-year EFS2 and overall survival rates after BM relapse were 37% ± 4% and 46% ± 4%, respectively, and rates after isolated EM relapse were 57% ± 5% and 71% ± 5%, respectively. By multivariate analysis, we found the duration of first remission to be the most significant predictor of EFS2 for either BM relapse or isolated EM relapse. Outcome was equivalent with SCT or chemotherapy after early or late relapse of SR-ALL at any site.

Conclusion

Duration of first remission remains the most significant predictor of outcome after either BM or isolated EM relapse of SR-ALL. Prognosis after early BM relapse remains poor and is not improved with SCT in this cohort.

Acute Lymphoblastic Leukemia: Diagnosis and Detection of Minimal Residual Disease Following Therapy

Flow cytometric immunophenotyping (FCI) is an important diagnostic modality in the evaluation of patients who have suspected or known acute lymphoblastic leukemia (ALL). It enables rapid identification, quantification, and immunophenotypic characterization of leukemic blasts, permitting accurate and timely diagnosis. Beyond facilitating the classification of ALL into fundamental diagnostic categories, FCI may anticipate recurrent cytogenetic and molecular abnormalities. FCI permits the detection of leukemic blasts after therapy at a level lower than that achievable by conventional microscopic examination. Flow cytometric detection of minimal residual disease is among the strongest prognostic factors in patients who have ALL and may provide an opportunity for more precise risk-adapted therapies.

Bone marrow stromal cells prevent apoptosis of lymphoma cells by upregulation of anti-apoptotic proteins associated with activation of NF-kappaB (RelB/p52) in non-Hodgkin's lymphoma cells

Stromal cells are an essential component of the bone marrow microenvironment that regulate or supports tumor survival. In this study we therefore studied the role of stromal cells in lymphoma cell survival. We demonstrated that adhesion of the B-cell lymphoma cell lines SUDH-4 and 10 to bone marrow stroma inhibited mitoxantrone-induced apoptosis. This adhesion-dependent inhibition of mitoxantrone-induced apoptosis correlated with decreased activation of caspases-8 and 9, and cleavage of caspase 3 and PARP. Electrophoretic mobility shift assays (EMSA) analysis demonstrated significantly increased NF-kappaB binding activity in lymphoma cells adhered to stroma cells compared to lymphoma cells in suspension. This DNA binding activity could be attributed to cell adhesion-mediated proteolysis of the NF-kappaB precursor, p100 (NF-kappaB2). This resulted in the generation of active p52, which translocated to the nucleus in complex with p65 and RelB. Coculture with stromal cells also induced expression of the NF-kappaB-regulated anti-apoptotic molecules, XIAP, cIAP(1) and cIAP(2). Inhibition of NF-kappaB significantly suppressed HS-5-induced protection against apoptosis in lymphoma cell lines as well as in primary lymphoma cells. Thus, bone marrow stroma protects B-cell lymphoma cells against apoptosis, at least in part through activation of NF-kappaB dependent mechanism involving up-regulation of NF-kappaB regulated antiapoptotic proteins. Consequently, this study suggests a new approach to decrease the resistance of lymphoma to chemotherapy.

Why and how to quantify minimal residual disease in acute lymphoblastic leukemia?

Several studies have demonstrated that monitoring of minimal residual disease (MRD) in childhood and adult acute lymphoblastic leukemia (ALL) significantly correlates with clinical outcome. MRD detection is particularly useful for evaluation of early treatment response and consequently for improved front-line therapy stratification. MRD information is also significant for children undergoing allogeneic hematopoietic stem cell transplantation and those with relapsed ALL. Currently, three highly specific and sensitive methodologies for MRD detection are available, namely multiparameter flow cytometric immunophenotyping, real-time quantitative polymerase chain reaction (RQ-PCR)-based detection of fusion gene transcripts or breakpoints, and RQ-PCR-based detection of clonal immunoglobulin and T-cell receptor gene rearrangements. In this review, characteristics, pitfalls, advantages and disadvantages of each MRD technique are critically discussed. The special emphasis is put on interlaboratory standardization, especially in view of the results obtained within the European collaborative BIOMED-1, BIOMED-2, and Europe Against Cancer projects and recent developments by European Study Group on MRD detection in ALL and EuroFlow Consortium. Standardized MRD techniques form the basis for stratification of patients into the risk groups in new treatment protocols mainly in childhood ALL. Only the results of these studies can answer the question whether MRD-based treatment intervention is associated with improved outcome.

End points to establish the efficacy of new agents in the treatment of acute leukemia

Federal regulations provide 2 pathways for approval of new agents for the treatment of acute leukemia, regular and accelerated approval. Regular approval requires evidence of clinical benefit, which is generally defined as either prolongation of life or improved quality of life, or an effect on an end point established as a surrogate for clinical benefit. Accelerated approval can be obtained based on demonstration of an effect on a surrogate measure "reasonably likely" to predict clinical benefit, but requires demonstration of clinical benefit after approval as well. The acute leukemias are a heterogeneous and relatively uncommon group of diseases. The design and execution of prospective randomized clinical trials demonstrating prolongation of life or improved quality of life for patients with these disorders can be difficult and costly and require lengthy follow-up. Thus, the development of novel trial design and inclusion of validated surrogate markers for clinical benefit are needed. To explore some of the issues pertinent to the choice of end points for drug approval in acute leukemia, the Food and Drug Administration invited the American Society of Hematology to participate in the organization and conduct of a joint workshop. In this report, we present the results of that effort.

The detection and significance of minimal residual disease in acute and chronic leukemia

Minimal residual disease (MRD) can be detected in many patients with leukemia who have achieved complete remission as defined by conventional pathology examination. The detection of MRD, be it by flow cytometry or by polymerase chain reaction assays, has now been found to be associated with subsequent relapses in most leukemia subtypes, either following chemotherapy or following hematopoietic stem cell transplantation. These assays are now increasingly used in clinical trial design to optimize therapy and provide a novel way to assess treatment efficacy.

Genes contributing to minimal residual disease in childhood acute lymphoblastic leukemia: prognostic significance of CASP8AP2

In childhood acute lymphoblastic leukemia (ALL), early response to treatment is a powerful prognostic indicator. To identify genes associated with this response, we analyzed gene expression of diagnostic lymphoblasts from 189 children with ALL and compared the findings with minimal residual disease (MRD) levels on days 19 and 46 of remission induction treatment. After excluding genes associated with genetic subgroups, we identified 17 genes that were significantly associated with MRD. The caspase 8-associated protein 2 (CASP8AP2) gene was studied further because of its reported role in apoptosis and glucocorticoid signaling. In a separate cohort of 99 patients not included in the comparison of gene expression profiles and MRD, low levels of CASP8AP2 expression predicted a lower event-free survival (P = .02) and a higher rate of leukemia relapse (P = .01) and were an independent predictor of outcome. High levels of CASP8AP2 expression were associated with a greater propensity of leukemic lymphoblasts to undergo apoptosis. We conclude that measurement of CASP8AP2 expression at diagnosis offers a means to identify patients whose leukemic cells are highly susceptible to chemotherapy. Therefore, this gene is a strong candidate for inclusion in gene expression arrays specifically designed for leukemia diagnosis.

Flow-cytometric immunophenotyping of normal and malignant lymphocytes

During the past two decades, flow-cytometric immunophenotyping of lymphocytes has evolved from a research technique into a routine laboratory diagnostic test. Extensive studies in healthy individuals resulted in detailed age-related reference values for different lymphocyte subpopulations in peripheral blood. This is an important tool for the diagnosis of hematological and immunological disorders. Similar, albeit less detailed, information is now available for other lymphoid organs, e.g., normal bone marrow, lymph nodes, tonsils, thymus and spleen. Flow-cytometric immunophenotyping forms the basis of modern classification of acute and chronic leukemias and is increasingly applied for initial diagnostic work-up of non-Hodgkin's lymphomas. Finally, with multiparameter flow cytometry, it is now possible to identify routinely and reliably low numbers of leukemia and lymphoma cells (minimal residual disease).

Clin Chem Lab Med 2006;44:775–96.

Long-term outcome in children with relapsed ALL by risk-stratified salvage therapy: results of trial acute lymphoblastic leukemia-relapse study of the Berlin-Frankfurt-Münster Group 87

PURPOSE

Approximately 20% of children with acute lymphoblastic leukemia (ALL) suffer a relapse, and their prognosis is unfavorable. Between 1987 and 1990, the multicenter trial Acute Lymphoblastic Leukemia-Relapse Study of the Berlin-Frankfurt-Münster Group (ALL-REZ BFM) 87 was conducted to establish a uniform treatment for these children in Germany and Austria.

PATIENTS AND METHODS

Of 207 registered patients, 183 patients were stratified into three groups according to the protocol: A, early bone marrow (BM) relapse (n = 56); B, late BM relapse (n = 101); C, isolated extramedullary relapse (n = 26). Treatment consisted of risk-adapted alternating short-course multiagent systemic and intrathecal chemotherapy, cranial irradiation, if indicated, and conventional maintenance therapy. Additionally, 24 patients with an exceptionally poor prognosis (early BM or any relapse of T-cell ALL) were treated with individual regimens. In 35 patients, stem-cell transplantation was performed.

RESULTS

The probability of event-free survival (EFS) and overall survival of all registered patients at 15 years was 0.30 +/- 0.03 and 0.37 +/- 0.03, respectively, with significant differences between the strategic groups (A, 0.18 +/- 0.05 and 0.20 +/- 0.05; B, 0.44 +/- 0.05 and 0.52 +/- 0.05; C, 0.35 +/- 0.09 and 0.42 +/- 0.10). Despite risk-adapted treatment, an early time point of relapse and T-lineage immunophenotype were significant predictors of inferior EFS in uni- and multivariate analyses.

CONCLUSION

With the ALL-REZ BFM 87 protocol, more than one-third of patients may be regarded as cured from recurrent ALL with second complete remissions lasting more than 10 years. Immunophenotype and time point of relapse are important prognostic factors that allow us to adapt more precisely treatment intensity to individual prognosis in future trials.

Childhood acute lymphoblastic leukaemia and relapse

Acute lymphoblastic leukaemia (ALL) is the most common childhood cancer. Treatment has improved but relapsed ALL remains more common than new cases of many 'common' paediatric malignancies. We have salvage regimens with substantial complete remission (CR) rates and increasing access to haematopoietic stem cell transplantation, but most patients who relapse die. We need better therapies. Insights into pharmacology may guide more effective use of existing agents. Novel agents with activity against resistant lymphoblasts offer an appealing strategy. However, most candidate agents fail, despite enthusiastic investigators, intriguing mechanisms of action and 'compelling' preclinical data. A number of existing combinations provide a 40% complete response rate in second or third relapse. Yet survival in third remission is <10%. Novel agents must, most likely, be integrated into multiagent combinations that provide a higher CR rate or better quality CR's than our conventional combinations in order to contribute substantially to cure. The march from bench to bedside requires careful consideration of the intermediate steps.

Individualized therapy for childhood acute lymphoblastic leukemia

In the field of oncology, a growing emphasis is now being placed on individualizing treatment in a way that maximizes chance for cure while minimizing unwanted side effects. In childhood acute lymphoblastic leukemia (ALL), several well-established clinical and biologic prognostic variables have traditionally been used to risk stratify therapy for individual patients. While this approach has been very successful, many relapses still occur unpredictably in patients characterized as having favorable features of their disease at diagnosis. Furthermore, it is likely that other children are overtreated. Therefore, current initiatives in childhood leukemia have focused on identifying new prognostic markers to refine treatment decision-making. Recent advances, which include the sequencing of the human genome, and technical developments in high-throughput genomics and proteomics, have facilitated these efforts. This review will chart the evolution of individualized therapy for ALL, the most common malignancy of children.

The seventh international childhood acute lymphoblastic leukemia workshop report: Palermo, Italy, January 29--30, 2005

Between 1995 and 2004, six International Childhood Acute Lymphoblastic Leukemia (ALL) Workshop have been held, and the completion of several collaborative projects has established the clinical relevance and treatment options for several specific genetic subtypes of ALL. This meeting report summarizes the data presented in the seventh meeting and the discussion.

Prognostic factors for relapsed childhood acute lymphoblastic leukemia: impact of allogeneic stem cell transplantation--a report from the Kyushu-Yamaguchi Children's Cancer Study Group

BACKGROUND

The treatment results of childhood acute lymphoblastic leukemia (ALL) with a first relapse were retrospectively analyzed to determine prognostic factors. In particular, an attempt was made to clarify whether stem cell transplantation (SCT) had any advantages over chemotherapy.

PROCEDURES

Of the 407 children with ALL diagnosed between 1984 and 1996, 117 suffered from a relapse before December 1999. The patients were treated differently according to the protocols of each institution. The potential prognostic factors examined were: the time of initial diagnosis, gender, immunophenotype of leukemic blasts and the NCI-risk classification at initial diagnosis, the site of relapse, the time of relapse (early: within 18 months after diagnosis, intermediate: other than either early or late relapse, late: later than 6 months after the discontinuation of front-line chemotherapy), and the treatment after relapse (chemotherapy alone and SCT).

RESULTS

A second complete remission (CR2) was achieved in 90 patients (77%) and thirty of them maintained CR2, thus resulting in an event-free survival rate (EFS) of 25.1% and an overall survival rate of 26.1%. The significant prognostic factors identified by a multivariate analysis included the time of relapse (EFS: early 16.2%, intermediate 23.9%, late 35.1%, P = 0.012) and the treatment after relapse (EFS: SCT 30.3%, chemotherapy 22.0%, P = 0.049). When patients with an isolated bone marrow relapse and continuous CR2 for more than 3 months were analyzed, the treatment in CR2 was the only independent prognostic factor (EFS: SCT 60.2%, chemotherapy 25.7%, P = 0.005).

CONCLUSIONS

In children with ALL and a first relapse, the time of relapse and the treatment after relapse were found to be independent prognostic factors. Allogeneic SCT in CR2 showed significantly better results than chemotherapy in patients with an isolated bone marrow relapse.

Bone marrow recurrence after initial intensive treatment for childhood acute lymphoblastic leukemia

BACKGROUND

The authors studied the clinical outcome of 106 children with acute lymphoblastic leukemia (ALL) who developed a bone marrow recurrence as the first adverse event after contemporary intensified therapy.

METHODS

Endpoints were the rates and lengths of second remission, the cumulative incidence of second hematologic recurrence, second event-free survival (EFS), and survival.

RESULTS

Bone marrow recurrences were isolated in 79 patients, and combined with an extramedullary site in 27 patients. The median time to recurrence was 2.6 years (range, 0.3-11.6 years). Seventy-six patients (71.7%) attained a second remission (median length, 0.7 year; range, 0.03-13.3 years). The 5-year survival probability among all patients was 24.2% +/- 4.2% (standard error). On multivariate analysis, time to first disease recurrence and blast cell lineage were found to be independent predictors of a second EFS (P = 0.008 and P = 0.028, respectively). The 5-year EFS estimate in patients with an initial disease remission of >/= 36 months was 42.6% +/- 7.8% but was only 12.5% +/- 3.9% among children with a short duration of disease remission (< 36 months). These estimates were 28.7% +/- 4.9% and 5.0% +/- 3.4%, respectively, for B blast and T blast cell lineages.

CONCLUSIONS

Despite acceptable long-term second EFS rates for certain subgroups, overall bone marrow recurrence after intensified first-line therapy for childhood ALL signals a poor outcome.

Comparative analysis of flow cytometry and polymerase chain reaction for the detection of minimal residual disease in childhood acute lymphoblastic leukemia

Minimal residual disease (MRD) is an independent prognostic factor in childhood acute lymphoblastic leukemia (ALL). The most widely applied MRD assays in ALL are flow cytometric identification of leukemia immunophenotypes and polymerase chain reaction (PCR) amplification of antigen-receptor genes. We measured MRD by both assays in 227 patients with childhood B-lineage ALL. Of 1375 samples (736 bone marrow and 639 peripheral blood) examined, MRD was <0.01% in 1200, and > or =0.01% in 129 by both assays; MRD levels measured by the two methods correlated well. Of the remaining 46 samples, 28 had MRD > or =0.01% by flow cytometry but <0.01% by PCR. However, PCR (which had a consistent sensitivity of 0.001%) detected leukemic gene rearrangements in 26 of these 28 samples. Conversely, in 18 samples, MRD was > or =0.01% by PCR but <0.01% by flow cytometry. In nine of these samples, flow cytometry had a sensitivity of 0.001%, and detected aberrant immunophenotypes in eight samples. Therefore, the two most widely used methods for MRD detection in ALL yield concordant results in the vast majority of cases, although the estimated levels of MRD may vary in some. The use of the two methods in tandem ensures MRD monitoring in all patients.