Presenting White Blood Cell Count and Kinetics of Molecular Remission Predict Prognosis in Acute Promyelocytic Leukemia Treated With All-Trans Retinoic Acid: Result of the Randomized MRC Trial

How I treat acute promyelocytic leukemia

Acute promyelocytic leukemia is the first malignant disease highly curable with targeted therapy directed at a unique molecular abnormality. The characteristic bleeding diathesis is the most notorious manifestation of the disease, which historically has accounted for a high mortality rate during induction. Acute promyelocytic leukemia is one of the few hematologic diseases that must be recognized under the microscope by the practicing hematologist because early institution of all-trans retinoic acid (ATRA) at the first suspicion of the disease before confirmation of the diagnosis and aggressive blood product support are critical to reduce early mortality. ATRA plus anthracycline-based chemotherapy for induction and consolidation followed by maintenance ATRA with low-dose chemotherapy is currently the standard of care. However, the combination of ATRA and arsenic trioxide, with minimal chemotherapy to control leukocytosis, is very effective therapy for newly diagnosed patients. This combination may replace conventional approaches for most, if not all, patients in the very near future. Acute promyelocytic leukemia should be considered in any patient with newly diagnosed acute myeloid leukemia because the treatment is urgent and different from all other subtypes.

Very long-term outcome of acute promyelocytic leukemia after treatment with all-trans retinoic acid and chemotherapy: the European APL Group experience

Acute promyelocytic leukemia (APL) is highly curable with the combination of all-trans retinoic acid (ATRA) and anthracycline-based chemotherapy (CT), but very long-term results of this treatment, when CT should be added to ATRA and the role of maintenance treatment, remain uncertain. In our APL93 trial that included 576 newly diagnosed APL patients, with a median follow-up of 10 years, 10-year survival was 77%. Maintenance treatment significantly reduced 10-year cumulative incidence of relapses, from 43.2% to 33%, 23.4%, and 13.4% with no maintenance, maintenance using intermittent ATRA, continuous 6 mercaptopurine plus methotrexate, and both treatments, respectively (P < .001). Maintenance particularly benefited patients with white blood cell (WBC) count higher than 5 x 10(9)/L (5000/microL). Early addition of CT to ATRA significantly improved 10-year event-free survival (EFS), but without significant effect on overall survival (OS). The 10-year cumulative incidence of deaths in complete response (CR), resulting mainly from myelosuppression, was 5.7%, 15.4%, and 21.7% in patients younger than 55, 55 to 65, and older than 65 years, respectively, supporting the need for less myelosuppressive treatments, particularly for consolidation therapy. This study is registered at http://clinicaltrials.gov as NCT00599937.

Treatment of children with acute promyelocytic leukemia: results of the first North American Intergroup trial INT0129

BACKGROUND

This report focuses on the children enrolled on the first North American Intergroup study of APL (INT0129). This study was designed to compare the rates of CR, disease-free survival (DFS), overall survival (OS) and toxicity of therapy with all-trans-retinoic acid (ATRA) for remission induction and/or maintenance compared to conventional chemotherapy in patients with previously untreated APL.

PROCEDURE

Fifty-three patients who were documented to have the t(15;17) translocation were able to be evaluated for toxicity of treatment, outcome of induction, and survival.

RESULTS

The overall CR rate was 81%. The estimated 5-year DFS from time of CR was 41% for all patients. The estimated 5-year OS for all patients from entry into the study was 69%. The 5-year DFS from time of CR for patients who were randomized to ATRA for induction or maintenance or both was 48% compared to 0% for patients who never received ATRA (P < 0.0001).

CONCLUSIONS

The most important finding of our study is that a significant DFS advantage exists for children with APL who received ATRA during induction or maintenance or both compared to children who received no ATRA. Furthermore, remissions in these children appear durable as the OS rates are stable at 10 years.

Quantitative detection of PML-RARalpha fusion transcript by real-time PCR with a single primer pair

Quantitative detection of minimal residual disease has prognostic value for some leukemias. Acute promyelocytic leukemia (APL) is characterized by the specific PML-RARalpha fusion gene from t(15;17). Added to three PML-RARalpha isoforms, alternative spliced forms of PML exons give rise to multiple isoforms even within a single patient. To date, multiple primer pairs for the detection of the various PML-RARalpha transcripts have been designed, potentially generating some nonspecific amplification products. Here, we established a real-time quantitative PCR (RQ-PCR) strategy with a single primer pair using LightCycler (sp-RQ-PCR), which could simultaneously detect three isoforms with equal specificity and sensitivity as well as alternative spliced forms. Results obtained with sp-RQ-PCR for 39 samples from 15 APL patients and 31 non-APL samples were compared with those with TaqMan assay with three primer pairs. In two of the APL samples, PML-RARalpha was detected in the TM, but not in the sp-RQ-PCR or nested PCR. Furthermore, the sp-RQ-PCR showed no positive results for the 31 non-APL samples, whereas the TM identified 13% (4/31) as positive. Electrophoresis detected some artifacts in the TM, which do not correspond to PML-RARalpha. We conclude that our sp-RQ-PCR is specific enough to identify various forms of PML-RARalpha and yields no false-positive results.

High dose ara-C in the treatment of newly diagnosed acute promyelocytic leukemia: long-term results of the German AMLCG

The objective of this study for newly diagnosed acute promyelocytic leukemia (APL) was to evaluate the efficacy of an intensified double induction chemotherapy including high dose ara-C (HD) and all-trans retinoic acid (ATRA) followed by consolidation and 3 years maintenance therapy. In contrast to APL studies stratifying therapy according to pretreatment white blood cell (WBC) count < and > or =10 x 10(9)/l (low/intermediate and high risk according to the Sanz score), our patients received uniform therapy. From 1994 to 2005, 142 patients (age, 16-60 years) were enrolled. In the low/intermediate (n=105) vs high (n=37) WBC group, the rates of complete remission were 95.2 vs 83.8%, of induction death were 4.8 vs 16.2% (P=0.05) and of molecular remission were 87.5 vs 91.3% (P=1). Long-term overall survival was 84.4 vs 73.0% (P=0.12), event free survival was 78.3 vs 67.3% (P=0.11), relapse free survival was 82.1 vs 80.0% (P=0.83) and the cumulative incidence of relapse was 7.4 vs 11.4% (P=0.46). No relapse or death occurred after 4.7 years. ATRA and intensified chemotherapy including HD ara-C followed by prolonged maintenance therapy reduced the relapse risk in high risk patients. Pretreatment WBC count > or =10 x 10(9)/l count was no relevant prognostic factor for relapse.

Clinical and Biological Significance of CD56 Antigen Expression in Acute Promyelocytic Leukemia

The biological significance of CD56 antigen expression in patients with acute promyelocytic leukemia (APL) has been under investigation. We investigated the clinical and biologic features of CD56+APL. In our series, CD56 antigen was positive in 4 of 28 (14%) APL patients. No differences were found regarding age, gender, performance status (PS), initial leukocyte and platelet counts, lactate dehydrogenase (LDH) and fibrinogen (Fbg) levels according to CD56 expression. CD34 antigen was co-expressed in 3 of the 4 patients with CD56+ APL, in contrast to 2 of the 24 patients with CD56- APL (P = .01). Extramedullary relapse occurred in 3 of the 4 patients with CD56+ APL, in contrast to none of the 24 patients with CD56- APL (P = .001). Median remission duration was 4 months in CD56+ APL and was not reached in CD56- APL. The CD56+ population had a shorter remission duration (P < .0001) and disease-free survival (P < .0001). In contrast, no difference was found in overall survival. These results suggested that CD56 expression was associated with the leukemogenetic mutation at the primitive hematopoietic progenitor cell level and extramedullary relapse in APL patients treated with ATRA and chemotherapy.

Prospective Minimal Residual Disease Monitoring to Predict Relapse of Acute Promyelocytic Leukemia and to Direct Pre-Emptive Arsenic Trioxide Therapy

Purpose

Molecular diagnostics and early assessment of treatment response that use methodologies capable of detecting submicroscopic disease can distinguish subgroups of patients with leukemia at differing relapse risk. Such information is being incorporated into risk-stratified protocols; however, there are few data concerning prospective use of sequential minimal residual disease (MRD) monitoring to identify more precisely those patients destined to experience relapse, which would allow more tailored therapies.

Methods

Real-time quantitative polymerase chain reaction (RQ-PCR) assays to detect leukemia-specific transcripts (ie, PML-RARA, RARA-PML) were used to prospectively analyze 6,727 serial blood and marrow samples from 406 patients with newly diagnosed acute promyelocytic leukemia (APL) who were receiving all-trans-retinoic acid and anthracycline-based chemotherapy.

Results

MRD monitoring according to the recommended schedule successfully identified the majority of patients subject to relapse and provided the most powerful predictor of relapse-free survival (RFS) in multivariable analysis (hazard ratio, 17.87; 95% CI, 6.88 to 46.41; P < .0001); MRD monitoring was far superior to presenting WBC (hazard ratio, 1.02; 95% CI, 1.00 to 1.03; P = .02), which is currently widely used to guide therapy. In patients who were predicted to experience relapse on the basis of MRD monitoring, early treatment intervention with arsenic trioxide prevented progression to overt relapse in the majority, and the RFS rate at 1 year from molecular relapse was 73%. By using this strategy, 3-year cumulative incidence of clinical relapse was only 5% in the Medical Research Council AML15 trial.

Conclusion

Rigorous sequential RQ-PCR monitoring provides the strongest predictor of RFS in APL and, when coupled with pre-emptive therapy, provides a valid strategy to reduce rates of clinical relapse. This provides a model for development of a more individualized approach to management of other molecularly defined subtypes of acute leukemia.

Adverse prognostic impact ofCDKN2Bhyper-methylationin acute promyelocytic leukemia

The use of all-trans retinoic acid (ATRA) has markedly improved the survival of patients with acute promyelocytic leukemia (APL), making it potentially curable. However, the identification of prognostic markers predictive of durable remission remains an important aspect in risk-adjusted treatment algorithms. High presentation leucocyte count has been found to correlate with inferior disease-free-survival (DFS). However, recent studies have also shown aberrant promoter methylation of the CDKN2B (alias p15) gene to be a negative prognostic factor. Promoter methylation results in the formation of a repressor complex, leading to chromatin compaction and suppression of gene expression and is, therefore, an alternative mechanism of gene inactivation. CDKN2B, a cyclin-dependent kinase inhibitor, is a tumor suppressor gene inhibiting cell cycle progression. The CpG island inside the CDKN2B promoter is hyper-methylated in approximately 50 - 60% of APL patients. CDKN2B methylation correlates negatively with DFS. As methylation-induced inactivation of CDKN2B pre-disposes to unchecked cellular proliferation, CDKN2B hyper-methylation is also associated with high presentation leucocyte count. Multivariate analysis in several studies, however, has shown that the negative prognostic impact of CDKN2B methylation is independent of its association with high leucocyte counts. Therefore, CDKN2B methylation is a potential prognostic factor that may be incorporated into a risk-stratified therapeutic strategy, which aims at achieving a cure with optimal amounts of treatment.

Improved Outcome of Acute Promyelocytic Leukemia With High WBC Counts Over the Last 15 Years: The European APL Group Experience

Purpose

Acute promyelocytic leukemia (APL) with pretreatment WBC counts greater than 10,000/μL is still considered to carry a poorer prognosis than APL with WBC lower than 10,000/mL. We evaluated outcome improvement in such patients in recent years.

Patients and Methods

Nine hundred two patients with APL, including 204 patients and 68 patients with WBC counts more than 10,000/μL and more than 50,000/μL, respectively, were enrolled between 1993 and 2005 in two successive randomized trials of the European APL group (APL 93 and APL 2000) that tested, in particular, the modalities of combination of all-trans retinoic acid (ATRA) and chemotherapy, maintenance treatment, escalating doses of cytarabine, early administration of dexamethasone, and CNS prophylaxis.

Results

Between the APL 93 and 2000 trials, the complete response (CR) rate increased from 89.6% to 93%, and the 5-year cumulative incidence of relapse (CIR) decreased from 40% to 9.5% in patients with WBC counts of 10,000 to 50,000/μL. In patients with WBC counts more than 50,000/μL, the CR rate increased from 82% to 91%, and 5-year CIR decreased from 59% to 24%. Whereas in the APL 93 trial, increased WBC counts were significantly associated with higher CIR and shorter survival, this was not the case in the APL 2000 trial. In patients with increased WBC counts, enrollment onto the APL 2000 trial (v APL 93) and combined maintenance with ATRA and chemotherapy were associated with significantly lower CIR and better survival.

Conclusion

Outcome of APL with high WBC count has markedly improved over the years as a result of fewer early deaths and fewer relapses. Better initial supportive care and combined maintenance treatment have contributed to this improvement.

Novel postremission strategies in adults with acute myeloid leukemia

PURPOSE OF REVIEW

Given the high rates of relapse in acute myeloid leukemia (AML), there is tremendous opportunity for the development of new therapeutic strategies in the postremission state. Unfortunately, the currently available modalities for postremission therapy, namely chemotherapy, have proven largely ineffective in changing the natural history of AML. The challenges to overcome therapeutic failure in the minimal residual disease status may relate to an incomplete understanding of the mechanisms and cell populations that are directly related to disease relapse as well as suboptimal ability to identify patients at highest risk for relapse.

RECENT FINDINGS

Being a heterogeneous disease, relapsed AML is unlikely to emanate from one predominant mechanism; instead, there are likely multiple biologic factors at play that allow for clinical relapse to occur. These factors likely include multidrug resistance proteins, aberrant signal transduction pathways, survival of leukemia stem cells, microenvironmental interactions, and immune tolerance. Many novel strategies are in development that target these mechanisms, ranging from chemotherapeutic modalities, to signal transduction inhibitors, to upregulation of antileukemic immune responses.

SUMMARY

Understanding the underlying mechanisms of leukemic cell survival and resistance has spurred the development of novel therapeutic approaches to overcome these mechanisms in the hope of eradicating minimal residual disease and improving survival in AML.

Effective treatment of acute promyelocytic leukemia with all-trans-retinoic acid, arsenic trioxide, and gemtuzumab ozogamicin

PURPOSE

We examined the outcome of patients with newly diagnosed acute promyelocytic leukemia (APL) treated with all-trans-retinoic acid (ATRA) and arsenic trioxide (ATO) with or without gemtuzumab ozogamicin (GO) but without traditional cytotoxic chemotherapy.

PATIENTS AND METHODS

From February 2002 to March 2008, 82 patients with APL were treated with a combination of ATRA plus ATO. The first cohort of 65 patients received ATRA and ATO (beginning on day 10 of ATRA). High-risk patients (WBCs >or= 10 x 10(9)/L) received GO on the first day. From July 2007, the second cohort of 17 patients received ATRA and ATO concomitantly on day 1. They also received GO on day 1, if high risk, and if their WBC increased to more than 30 x 10(9)/L during induction. Monitoring for PML-RARA fusion gene was conducted after induction and throughout consolidation and follow-up.

RESULTS

Overall, 74 patients achieved complete remission (CR) and one achieved CR without full platelet recovery after the induction, for a response rate of 92%. Seven patients died at a median of 4 days (range, 1 to 24 days) after inclusion in the study from disease-related complications. The median follow-up is 99 weeks (range, 2 to 282 weeks). Among the responding patients, three experienced relapse at 39, 52, and 53 weeks. Three patients died after being in CR for 14, 21, and 71 weeks, all from a second malignancy. The estimated 3-year survival rate is 85%.

CONCLUSION

The combination of ATRA and ATO (with or without GO) as initial therapy for APL was effective and safe and can substitute chemotherapy-containing regimens.

Acute promyelocytic leukemia: a paradigm for differentiation therapy

Acute promyelocytic leukemia(APL) is characterized by the t(15;17) chromosomal translocation leading to the formation of the PML-RARalpha oncoprotein. This leukemia has attracted considerable interest in recent years, being the first in which therapies that specifically target the underlying molecular lesion, i.e., all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), leading to induction of differentiation and apoptosis have been successfully used in clinical practice. The advent of ATRA therapy has transformed APL from being a disease with a poor outlook to one of the most prognostically favorable subsets of acute myeloid leukemia. Further improvements in outcome may be achieved with the use of ATO, which achieves high rates of remission in the relatively small proportion of patients now relapsing following standard first-line therapy with ATRA and anthracycline-based chemotherapy. Moreover, recent studies have suggested that ATO and ATRA, or even ATO alone, used as front-line treatment of PML-RARA- associated APL can induce long-term remissions. This raises the possibility that some patients can be cured using differentiation therapies alone, without the need for chemotherapy, thereby potentially reducing treatment-related toxicity. It is clear that the success of such an approach is critically dependent upon molecular diagnostics and monitoring for minimal residual disease (MRD) to distinguish those patients who can potentially be cured with differentiation therapy from those requiring additional myelosuppressive agents. This represents an exciting new phase in the treatment of acute leukemia, highlighting the potential of molecularly targeted and MRD-directed therapies to achieve an individualized approach to patient management.

Methods for counting particles in microfluidic applications

Microfluidic particle counters are important tools in biomedical diagnostic applications such as flow cytometry analysis. Major methods of counting particles in microfluidic devices are reviewed in this paper. The microfluidic resistive pulse sensor advances in sensitivity over the traditional Coulter counter by improving signal amplification and noise reduction techniques. Nanopore-based methods are used for single DNA molecule analysis and the capacitance counter is useful in liquids of low electrical conductivity and in sensing the changes of cell contents. Light-scattering and light-blocking counters are better for detecting larger particles or concentrated particles. Methods of using fluorescence detection have the capability for differentiating particles of similar sizes but different types that are labeled with different fluorescent dyes. The micro particle image velocimetry method has also been used for detecting and analyzing particles in a flow field. The general limitation of microfluidic particle counters is the low throughput which needs to be improved in the future. The integration of two or more existing microfluidic particle counting techniques is required for many practical on-chip applications.

Management of acute promyelocytic leukemia: recommendations from an expert panel on behalf of the European LeukemiaNet

The introduction of all-trans retinoic acid (ATRA) and, more recently, arsenic trioxide (ATO) into the therapy of acute promyelocytic leukemia (APL) has revolutionized the management and outcome of this disease. Several treatment strategies using these agents, usually in combination with chemotherapy, but also without or with minimal use of cytotoxic agents, have provided excellent therapeutic results. Cure of APL patients, however, is also dependent on peculiar aspects related to the management and supportive measures that are crucial to counteract life-threatening complications associated with the disease biology and molecularly targeted treatment. The European LeukemiaNet recently appointed an international panel of experts to develop evidence- and expert opinion-based guidelines on the diagnosis and management of APL. Together with providing current indications on genetic diagnosis, modern risk-adapted front-line therapy and salvage treatment, the review contains specific recommendations for the identification and management of most important complications such as the bleeding disorder, APL differentiation syndrome, QT prolongation and other ATRA- and ATO-related toxicities, as well as for molecular assessment of response to treatment. Finally, the approach to special situations is also discussed, including management of APL in children, elderly patients, and pregnant women.

Retinoic acid syndrome: a review

The retinoic acid syndrome (RAS) is an unpredictable but frequent complication which may develop after administration of all-trans retinoic acid (ATRA) most commonly in patients with acute promyelocytic leukaemia (APL). In this review, we describe the incidence, predictive factors, clinical course, outcome and treatment of RAS in patients with APL treated with ATRA. The incidence of RAS in patients receiving ATRA is about 14-16%, with an associated mortality of about 2%. Initial high white blood cell (WBC) count, rapidly increasing WBC count and/or the presence of the CD 13 expression on leukaemic cells may help in identifying patients likely to develop RAS. Concurrent chemotherapy will probably decrease the risk of developing RAS but often exacerbates bleeding, leading to leucocytosis, thrombocytopenia, disseminated intravascular coagulation and fibrinolysis. Prophylactic steroids are not recommended but prompt administration of steroids at the first sign of unexplained dyspnea, fever, weight gain or pulmonary infiltrate, is critical. Liposomal ATRA is being investigated to induce haematological cure in APL without chemotherapy and to reduce the incidence of RAS but further validation of its usefulness is necessary.

All-trans-retinoic acid and arsenic trioxide as initial therapy for acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is a rare subtype of acute myeloid leukemia (AML). Treatment of pediatric APL is based on the combination of all-trans-retinoic acid (ATRA), an anthracycline and cytosine arabinoside. Arsenic trioxide (ATO) has been studied in adults with newly diagnosed or relapsed APL with excellent response rates both when used as a single agent or in combination with ATRA or ATRA plus chemotherapy. There is little data on combination therapy with ATRA and ATO in pediatric APL. We present a case of an adolescent male with APL who was treated using ATRA and ATO without conventional chemotherapy agents.

Molecular and chromosomal alterations: new therapies for relapsed acute myeloid leukemia

Acute myeloid leukemia (AML) remains the most common form of leukemia and the most common cause of leukemia death. Although conventional chemotherapy can cure between 25 and 45% of AML patients, the majority of patients die after relapse or of complications associated with treatment. Thus, more specific and less toxic treatments for AML patients are needed, especially for elderly patients. An indispensable prerequisite to investigate tailored approaches for AML is the recent progress in the understanding the molecular features that distinguish leukemia progenitors from normal hematopoietic counterparts and the identification of a variety of dysregulated molecular pathways. This in turn would allow the identification of tumor-specific characteristics that provide a rational basis for the development of more tailored, and hence potentially more effective and less toxic, therapeutic approaches. In this review, we describe some of the signaling pathways that are aberrantly regulated in AML, with a specific focus on their pathogenetic and therapeutic significance, and we examine some recent therapies directed against these targets, used in clinical trial for relapsed patients or unfit for conventional chemotherapy.

Causes and prognostic factors of remission induction failure in patients with acute promyelocytic leukemia treated with all-trans retinoic acid and idarubicin

An understanding of the prognostic factors associated with the various forms of induction mortality in patients with acute promyelocytic leukemia (APL) has remained remarkably limited. This study reports the incidence, time of occurrence, and prognostic factors of the major categories of induction failure in a series of 732 patients of all ages (range, 2-83 years) with newly diagnosed APL who received all-trans retinoic acid (ATRA) plus idarubicin as induction therapy in 2 consecutive studies of the Programa de Estudio y Tratamiento de las Hemopatias Malignas (PETHEMA) Group. Complete remission was attained in 666 patients (91%). All the 66 induction failures were due to induction death. Hemorrhage was the most common cause of induction death (5%), followed by infection (2.3%) and differentiation syndrome (1.4%). Multivariate analysis identified specific and distinct pretreatment characteristics to correlate with an increased risk of death caused by hemorrhage (abnormal creatinine level, increased peripheral blast counts, and presence of coagulopathy), infection (age >60 years, male sex, and fever at presentation), and differentiation syndrome (Eastern Cooperative Oncology Group [ECOG] score >1 and low albumin levels), respectively. These data furnish clinically relevant information that might be useful for designing more appropriately risk-adapted treatment protocols aimed at reducing the considerable problem of induction mortality in APL.

A comprehensive review of acute promyelocytic leukemia in children

The outcome of patients with acute promyelocytic leukemia (APL) has substantially improved since the successful introduction of tretinoin, and nowadays combining tretinoin with chemotherapy is potentially curative for at least 70-75% of patients with newly diagnosed APL. In most pediatric series, APL represents < or = 10% of childhood acute myelogenous leukemia. APL in children is more common in girls and in obese children. It is characterized by a higher incidence of hyperleukocytosis, an increased incidence of microgranular morphology and by more frequent occurrence of the PML/RARalpha isoforms bcr 2 and bcr 3 compared to adults. Tretinoin-based therapy is curative for the majority of children with APL. Recent data indicate that > or = 2 negative RT-PCR assays for PML/RARalpha on bone marrow performed at least 1 month apart after completing therapy are strongly associated with long-term remissions, while conversion to PCR positivity for PML/RARalpha during remission is highly predictive of impending relapse. Data from recent studies in adults and limited data from children show that arsenic trioxide is the single most effective agent in APL and deserves immediate study in newly diagnosed children in an effort to further improve prognosis and to limit exposure to conventional cytotoxic chemotherapy.

PML-RARalpha inhibitors (ATRA, tamibaroten, arsenic troxide) for acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is characterized by generation of the PML-RARalpha fusion gene. PML-RARalpha can homodimerize with another PML-RARalpha, and the hybrid binds the histone-deacetylase recruiting co-repressor complex with higher affinity than the wild-type RARalpha. However, the co-repressor complex is releasable by pharmacological doses of all-trans retinoic acid (ATRA). More than 90% of patients with APL achieve a complete remission (CR) with differentiation therapy consisting of ATRA combined with chemotherapy. A new synthetic retinoid, tamibaroten, showed therapeutic effectiveness in patients with ATRA-resistant APL with increased expression of cellular retinoic acid binding protein (CRABP), and about 60% of patients with relapsed APL achieved a CR. Arsenic trioxide triggers the rapid degradation of PML-RARalpha through the targeting of the PML moieties of the fusion protein and showed a high CR rate in relapsed APL. The combination of ATRA, chemotherapy, and/or new agents improved the long-term survival in patients with APL.

A randomized study with or without intensified maintenance chemotherapy in patients with acute promyelocytic leukemia who have become negative for PML-RARα transcript after consolidation therapy: The Japan Adult Leukemia Study Group (JALSG) APL97 study

To examine the efficacy of intensified maintenance chemotherapy, we conducted a prospective multicenter trial in adult patients with newly diagnosed acute promyelocytic leukemia treated with all-trans retinoic acid and chemotherapy. Of the 302 registered, 283 patients were assessable and 267 (94%) achieved complete remission. Predicted 6-year overall survival in all assessable patients and disease-free survival in patients who achieved complete remission were 83.9% and 68.5%, respectively. A total of 175 patients negative for PML-RARα at the end of consolidation were randomly assigned to receive either intensified maintenance chemotherapy (n = 89) or observation (n = 86). Predicted 6-year disease-free survival was 79.8% for the observation group and 63.1% for the chemotherapy group, showing no statistically significant difference between the 2 groups (P = .20). Predicted 6-year survival of patients assigned to the observation was 98.8%, which was significantly higher than 86.2% in those allocated to the intensified maintenance (P = .014). These results indicate that the intensified maintenance chemotherapy did not improve disease-free survival, but rather conferred a significantly poorer chance of survival in acute promyelocytic leukemia patients who have become negative for the PML-RARα fusion transcript after 3 courses of intensive consolidation therapy.

Hematopoietic cell transplantation in acute promyelocytic leukemia: a comprehensive review

The past three decades have brought major therapeutic advances in the management of acute promyelocytic leukemia. The current state-of-the-art induction treatment with all-trans retinoic acid in combination with anthracycline-based chemotherapy results in long-lasting remissions and cure in up to 70% of newly diagnosed patients. Unfortunately, treatment failure still occurs in one-third of patients. When disease relapses, patients can achieve subsequent remissions with arsenic trioxide, all-trans retinoic acid with or without chemotherapy, or other therapies. Patients achieving molecular remissions after salvage therapy are generally considered candidates for high-dose chemotherapy and autologous hematopoietic cell transplantation as a postconsolidation strategy. On the other hand, patients with evidence of persistent hematologic or molecular disease after salvage therapy could be offered allogeneic hematopoietic transplantation if a suitable HLA-donor is identified and the patient's overall performance and clinical condition are permissible. We hereby provide a comprehensive review and analysis of published clinical trials that evaluate the role of hematopoietic cell transplantation across different stages of acute promyelocytic leukemia.

Hematopoietic stem cell transplantation for adults with acute promyelocytic leukemia in the ATRA era: a survey of the European Cooperative Group for Blood and Marrow Transplantation

We performed a survey of the European Cooperative Group for Blood and Marrow Transplantation to analyze the outcome of 625 acute promyelocytic leukemia (APL) patients transplanted with auto- or allogeneic-hematopoietic stem cell transplantation (autoHSCT, alloHSCT) after 1993, in first (CR1) or in second complete remission (CR2). Leukemia-free survival (LFS) at 5 years in CR1 was 69% for 149 patients autografted and 68% for 144 patients allografted, whereas in CR2, LFS was 51% in 195 autoHSCT and 59% in 137 alloHSCT recipients, respectively. In the group of autoHSCT for CR1 (n=149), higher relapse incidence (RI) was associated with shorter time from diagnosis to transplant (<7.6 months); transplant-related mortality (TRM) was increased in older patients (>47 years), whereas for CR2, longer time from diagnosis to transplant (>18 months) was associated with increased LFS and decreased RI. In the alloHSCT group for CR1 (n=144), age (<33 years) was associated with increased LFS and decreased TRM and for CR2 (n=137), the use of mobilized peripheral blood stem cells was associated with decreased TRM. Female recipient, a female donor to male recipient and transplants performed before 1997 were associated with decreased RI. In conclusion, HSCT still appears to have a role in APL, especially for patients in CR2.

A new cytogenetic abnormality, t(2;7)(q33;q36), in acute promyelocytic leukemia

We report the case of a patient with acute promyelocytic leukemia (APL) carrying a novel chromosomal abnormality, t(2;7)(q33;q36). The 54-year-old woman was morphologically diagnosed with APL through bone marrow aspiration. The proportion of blast cells in bone marrow was 78%, including cells displaying Auer rods and faggot cells. Chromosomal analysis revealed the karyotype 46,XX,t(2;7)(q33;q36)[17]/46,XX[3]. The t(15;17) was not detected with conventional cytogenetic analysis. However, reverse transcriptase-polymerase chain reaction revealed the presence of a PML/RARA fusion gene. Cells displaying t(2;7)(q33;q36) disappeared after complete remission was achieved, using induction chemotherapy. Although several additional chromosomal abnormalities have been reported, this t(2;7)(q33;q36) without the classic t(15;17) represents a novel chromosomal abnormality associated with APL.

Optimizing treatment for elderly patients with acute promyelocytic leukemia: is it time to replace chemotherapy with all-trans retinoic acid and arsenic trioxide?

This review focuses on the treatment of acute promyelocytic leukemia (APL) in elderly patients and offers recommendations for improving outcomes. Nineteen percent of patients with APL are > or =60 years. Rates of response and survival are lower in elderly compared with younger patients, owing to a higher incidence of early deaths or deaths in remission. However, relapse-free survival rates are similar in both groups. Ongoing trials assess the role of reduced-intensity regimens. All-trans retinoic acid (ATRA) and concurrent arsenic trioxide is associated with high rates of response and molecular remission and low rates of induction deaths. We propose this combination as the treatment of choice in patients with APL, including the elderly. Patients with elevated leukocyte counts may also benefit from gemtuzumab ozogamicin therapy, with or without leukapheresis. Monitoring major organ function and toxicity is essential. Patients should be assessed for minimal residual disease using polymerase chain reaction testing for promyelocytic leukemia-retinoic acid receptor alpha. If molecular relapse is evident, treatment with ATRA and idarubicin, with or without gemtuzumab ozogamicin, is recommended.

Outcome of patients with acute promyelocytic leukemia failing to front-line treatment with all-trans retinoic acid and anthracycline-based chemotherapy (PETHEMA protocols LPA96 and LPA99): benefit of an early intervention

To determine prognosis of acute promyelocytic leukemia (APL) failing to front-line therapy with all-trans retinoic acid (ATRA) and anthracyclines, outcome of 52 patients (32 M/20 F; age: 37, 3-72) included in PETHEMA trials LPA96 and LPA99 who presented with either molecular failure (MOLrel, n=16) or hematological relapse (HEMrel, n=36) was analyzed. Salvage therapy consisted of ATRA and high-dose ara-C-based chemotherapy (HDAC) in most cases (83%), followed by stem-cell transplantation (autologous, 18; allogeneic, 10; syngeneic, 1). Fourteen patients with MOLrel (88%) achieved second molecular complete response (molCR), whereas 81% HEMrel patients responded to second-line treatment, with 58% molCR. After median follow-up of 45 months, four MOLrel and 18 HEMrel patients, respectively, experienced a second relapse. Outcome after MOLrel compared favorably to HEMrel, with longer survival (5-year survival: 64+/-14 vs 24+/-8%, P=0.01) and lower relapse risk (5-year relapse risk: 30+/-13 vs 64+/-9%; P=0.044). Additionally, age <or=40 and male gender were favorable variables for survival, whereas molecular response predicted longer leukemia-free survival. In conclusion, early institution of salvage therapy at molecular failure, before onset of hematological relapse, is beneficial in APL. Moreover, given the poor outcome of HEMrel managed with ATRA and HDAC, use of alternative therapeutic strategies in this setting is warranted.

Mutant Transcription Factors and Tyrosine Kinases as Therapeutic Targets for Leukemias: From Acute Promyelocytic Leukemia to Chronic Myeloid Leukemia and Beyond

Mutations in transcription factors (TFs) and protein tyrosine kinases (PTKs), which result in inhibition of differentiation/apoptosis or enhanced proliferative/survival advantage of hematopoietic stem/progenitor cells, are two classes of the most frequently detected genetic abnormalities in leukemias. The critical roles for mutant TFs and/or PTKs to play in leukemogenesis, and the absence of mutant TFs/PTKs in normal hematopoietic cells, suggest that the two types of aberrant molecules may serve as ideal therapeutic targets. The great success of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) in treating acute promyelocytic leukemia through modulation of the causative PML-RARalpha oncoprotein represents the first two paradigms of mutant TFs-targeting therapeutic strategies for leukemia. More recently, tyrosine kinase inhibitor STI-571/Imatinib mesylate/Gleevec in the treatment of Breakpoint Cluster Region-Abelson (BCR-ABL) positive leukemia elicits paradigm of mutant PTKs as ideal antileukemia targets. Thus to further improve clinical outcome of leukemia patients, elucidation of pathogenesis of leukemia, screening for oncoprotein-targeting small molecules, as well as rationally designed combination of drugs with potential synergy are of importance.

Front line clinical trials and minimal residual disease monitoring in acute promyelocytic leukemia

In spite of the very high cure rate (70%-80%) achieved in APL with combinatorial all-trans retinoic acid (ATRA) and anthracycline-based chemotherapy regimens, a number of issues are still open for investigation in front-line therapy of this disease. These include, among others, improvements in early death rate, the role of arsenic trioxide (ATO) and maintenance treatment, and, finally, optimization of molecular monitoring to better identify patients at increased risk of relapse. The current consensus on the most appropriate induction therapy consists of the concomitant administration of ATRA and anthracycline-based chemotherapy. Although the antileukemic benefit provided by the addition of ATRA to consolidation therapy has not been demonstrated in randomized studies, historical comparisons of consecutive studies carried out by Spanish and Italian cooperative groups suggest that the combination of ATRA and chemotherapy for consolidation may also contribute to improving therapeutic results. While a variety of distinct treatments are being investigated for front-line therapy, most experts agree that a risk-adapted therapy represents the optimal approach, through the use of more intensive therapy in patients with initial hyperleukocytosis. Longitudinal RT-PCR of PML/RARalpha allows sensitive assessment of response to treatment and minimal residual disease (MRD) monitoring in APL. Achievement of negative PCR status or molecular remission at the end of consolidation is now universally accepted and recommended as a therapeutic objective in this disease. On the other hand, persistence of, or conversion to, PCR positive in the marrow during follow-up is associated with impending relapse. Preliminary studies on therapy of molecular relapse indicate a survival advantage as compared to administering salvage treatment at time of hematologic relapse. The more accurate and reproducible real-time PCR method to detect at quantitative levels the PML/RARalpha hybrid will likely provide better inter-laboratory standardization and trial results comparison in the near future.

Treatment of acute promyelocytic leukemia by retinoids

We review the role of all-trans retinoic acid (ATRA) in the treatment of acute promyelocytic leukemia (APL). The combination of ATRA and conventional anthracycline-ARA-C chemotherapy (CT) has clearly demonstrated its superiority over CT alone (in terms of relapse and survival) in newly diagnosed APL. Combination treatment probably also reduces the incidence of initial failures, and complete remission (CR) rates greater than 90% are now regularly reported in large multicenter trials. Some randomized studies strongly suggest that prolonged maintenance treatment (for 1 or 2 years) with ATRA and low-dose CT, and possibly very early introduction of anthracycline CT during induction treatment, may reduce the incidence of relapse. With those treatments, the relapse risk appears to be only 10%-15%, although it remains greater in patients who initially have high white blood cell counts (often associated with variant M3 morphology, short bcr3 isoform, etc.) and patients with residual disease detectable by RT-PCR at the end of consolidation courses. In those patients, addition of arsenic derivatives to induction or consolidation treatment (or both treatments together) may prove useful and is currently being tested. ATRA syndrome (now generally called APL differentiation syndrome, as it is also seen with arsenic derivatives) remains the major side effect of ATRA treatment. It occurs in 10%-15% of patients and is currently fatal in at least 10% of them. Rapid onset of CT or high dose steroids (or both) should improve its outcome. A sizeable proportion of APL patients who relapse after ATRA and CT can be durably salvaged by the same treatment followed by allogeneic or autologous stem cell transplantation, provided the transplant (in the autologous setting) is RT-PCR-negative. However, in relapsing APL arsenic derivatives (mainly arsenic trioxide) are now considered to be the reference treatment. Some of the current issues with ATRA treatment in newly diagnosed APL include whether ATRA has a role during consolidation treatment and whether arabinoside (AraC) is required in addition to anthracyclines in the chemotherapy combined to ATRA.

Real-time PCR analysis of PML-RARα in newly diagnosed acute promyelocytic leukaemia patients treated with arsenic trioxide as a front-line therapy

BACKGROUND

Recently, patients with acute promyelocytic leukaemia (APL) have experienced significant clinical gains after treatment with arsenic trioxide. However, the use of this agent as a front-line therapy for newly diagnosed patients is unclear.

PATIENTS AND METHODS

Of 95 newly diagnosed APL patients, 85 patients who achieved complete remission (CR) were sequentially evaluated during a 4-60 month period by conventional RT-PCR. A total of 30 patients (six relapsed and 24 in continued CR) were selected and monitored by quantitative real-time PCR (RQ-PCR) assay. The PML-RARalpha fusion transcripts values were normalised to every 10(6) copies of G6PDH transcripts (NQ).

RESULTS

RQ-PCR analyses showed a rapid rate of clearance of NQ levels during the courses of arsenic therapy. In the majority of patients in CR, the NQ levels were below 5 x 10(2) in peripheral blood (PB) samples. In all the relapsed cases with follow-up intervals of 1-6 months (median 3 months) clinical relapse was predictable by increasing NQ level above this threshold.

CONCLUSIONS

Our study highlights the usefulness of PB and the definition of threshold level for early prediction of relapse. The threshold level correlates well with risk of relapse; therefore, transcript ratio below the level should be regarded as a goal in the clinical management of this disease.

A survival study and prognostic factors analysis on acute promyelocytic leukemia at a single center

This study was aimed to investigate the factors influencing long-term survival on patients with acute promyelocytic leukemia. Here, we present a single center retrospective study with long-term follow-up to explore the prognostic factors and a rationale of the using of ATRA, chemotherapy and As(2)O(3) in the treatment of newly diagnosed APL patients. In total, 222 patients, 184 achieved complete remission (CR) with the CR rate of 82.88% and 22 patients died during early induction therapy with the early-death-rate of 10%. Total 171 newly diagnosed APL patients entering CR were retrospectively analyzed from November 1989 to December 2004,with a median follow-up of 36 months (6-185 months). Univariate and multivariate analysis of eight factors potentially influencing survival and prognosis were carried out with Log-Rank and Cox regression method, including sex, age, initial WBC count, the level of lactic dehydrogenase (LDH), first induction regimen, days from induction therapy to CR, post-remission therapy and the status of PML-RAR alpha fusion gene by reverse transcription-polymerase chain reaction (RT-PCR). The results showed that the estimated 5-year overall survival (OS) and relapse-free survival (RFS) were 80.9+/-4.0 and 71.0+/-4.0%, respectively. Univariate analyses showed that initial WBC count, first induction regimen, days from induction therapy to CR, post-remission therapy regimen and the status of PML-RAR alpha in remission were important prognostic factors for long-term survival. Multivariate study showed that only post-remission therapy regimen was associated with RFS and OS. It is concluded that the post-remission treatment combining ATRA, As(2)O(3) and chemotherapy would significantly improve the long-term survival of APL patients achieving CR(1).

Minimal residual disease directed therapy for childhood acute myeloid leukaemia: the time is now

The continued improvement in the prognosis of childhood acute myeloid leukaemia (AML) has been paralleled by the use of increasingly intensive therapy. This has led to attempts to develop risk-directed strategies in which the most intensive treatment is reserved for those at highest risk of relapse. Unfortunately, current approaches, which rely on cytogenetic sub-grouping and morphological assessment of response to therapy, are inaccurate. New prognostic factors are needed. This annotation proposes that the introduction of protocols based on the measurement of minimal residual disease (MRD) holds the key to progression from an era of 'cure at all costs' to a more individualised approach. However, the full potential of MRD technologies will only be realised through properly designed studies with scrupulous attention to logistics and quality assurance. The article illustrates which children may benefit most from MRD analysis in AML and explores practical issues that should be addressed in the design of clinical trials.

Molecular response in acute promyelocytic leukemia: a direct comparison of regular and real-time RT-PCR

Evaluation of molecular response is important for the diagnosis and monitoring of minimal residual disease in patients with acute promyelocytic leukemia (APL). In this study, we analyzed the molecular response by regular reverse transcription-polymerase chain reaction (RT-PCR) and quantitative real-time RT-PCR in 31 newly diagnosed patients. The real-time RT-PCR results are reported as normalized DoseN and log-reduction (3.0-4.9 log-reduction as minor and > or =5.0 log-reduction as major molecular response). After induction therapy and completion of consolidation, minor molecular response was documented in 35.5 and 96.8% patients, respectively, which was equivalent to the regular RT-PCR (22.6 and 96.8%), whereas the major molecular response rate was significantly lower (12.9 and 90.3%, respectively). All patients achieved major molecular response during and after maintenance therapy. During the follow-up study, loss of major molecular response was observed in two patients, which was associated with subsequent loss of minor molecular response, positive RT-PCR and then documentation of central nervous system leukemia or clinical relapse in 3-6 months. For summary, we demonstrated that the real-time RT-PCR is potentially superior to regular RT-PCR in evaluation of molecular response in APL patients and that reporting real-time RT-PCR data by log-reduction is feasible and clinically relevant.

Use of all-trans retinoic acid plus arsenic trioxide as an alternative to chemotherapy in untreated acute promyelocytic leukemia

We examined whether combining all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) might be an alternative to ATRA plus chemotherapy in untreated acute promyelocytic leukemia (APL). Twenty-five low-risk patients (white blood cell [WBC] count less than 10 × 109/L [10 000/μL]) received ATRA (45 mg/m2 daily) and ATO (0.15 mg/kg daily, beginning day 10 of ATRA), and in complete remission (CR) received ATO plus ATRA, without chemotherapy, unless they were reverse transcriptase–polymerase chain reaction (RT-PCR)–positive 3 months from CR date or had molecular relapse. Nineteen high-risk patients were treated identically, but received chemotherapy, generally 9 mg/m2 gemtuzumab ozogamycin (GO) on day 1 of induction. The CR rate was 39 of 44 (24 of 25 in low-risk, 15 of 19 in high-risk). Disease recurred at 9, 9, and 15 months, respectively, in 3 high-risk patients. The median follow-up time from CR date in the 36 patients alive in first CR is 16 months (15 months in low-risk, 20 months in high-risk), with 9 patients followed for at least 24 months. Each of the 36 patients was PCR-negative at last follow-up. Thus, none of the low-risk patients has received chemotherapy, and only 3 high-risk patients (the 3 with relapsed disease) have received chemotherapy past induction. ATRA plus ATO may serve as an alternative to chemotherapy in low-risk untreated APL (eg, in older patients) and, when combined with GO, may improve outcome in high-risk patients.

Advances in the treatment for haematological malignancies

Despite the progress made in the last decade in the treatment of haematological malignancies, most of the patients still have a dismal prognosis. However, the improved knowledge of tumour biology opened the possibility to develop new 'intelligent' therapeutic strategies, the so-named targeted therapies. These approaches aim to selectively kill cancer cells by basing this selectivity on both the expression of a specific molecule on their surface or the activation of particular molecular pathways secondary to malignant transformation. In this article, the authors review the main targeted therapies available in haematology, such as monoclonal antibodies, tyrosine kinase, farnesyltransferase, as well as proteasome inhibitors, antiangiogenesis compounds and antisense oligonuceotides. Finally, the authors focus on the application of imatinib mesylate in chronic myeloid leukaemia as the paradigm of molecular treatment. Although these novel therapies are beginning to fulfil their promise, continued research efforts are needed to determine the optimal role of these strategies in haemato-oncology.

Practice points, consensus, and controversial issues in the management of patients with newly diagnosed acute promyelocytic leukemia

Recent reviews on acute promyelocytic leukemia (APL) treatment have focused on comparing therapeutic approaches, including all-trans retinoic acid (ATRA) and chemotherapy, and do not address several other aspects of APL management that are relevant to the outcome in individual patients. These aspects include appropriate diagnostic tools and strategies, supportive care, recognition and treatment of life-threatening complications, evaluation of response, and, finally, management of the disease in special conditions such as older patients and pregnant women. In addition to reviewing current consensus and controversies of ATRA and chemotherapy treatment, this article addresses the above issues of APL management with special emphasis on aspects that distinguish APL from other acute myelogenous leukemias.

Treatment of acute promyelocytic leukemia

Cure of acute promyelocytic leukemia (APL) is now a possibility for most patients through the use of state-of-the-art treatments, which include simultaneous administration of all-trans retinoic acid (ATRA) and anthracycline-based chemotherapy for induction and consolidation, as well as ATRA-based maintenance. Risk-adapted strategies to modulate treatment intensity may be an effective approach to minimize therapy-related morbidity and mortality while maintaining the potential of cure. In this context, there is no role for hematopoietic stem cell transplantation (HSCT) in front-line therapy, except for the small fraction of patients with persistent minimal residual disease at the end of consolidation. However, HSCT plays an important role for patients in second complete remission. In contrast, an increasing role of arsenic trioxide (ATO) is emerging. Given the high antileukemic efficacy observed with ATO in patients relapsing after ATRA-containing regimens, this agent is currently regarded as the best treatment option in this setting. However, until a randomized comparison between the standard therapy and ATO-based regimens in front-line therapy is available, this latter approach should only be recommended for unfit patients for whom chemotherapy is contraindicated. In addition to reviewing current consensus and controversial issues on antileukemic strategies, this review addresses other aspects that can be crucial for the outcome of individual patients. These aspects include supportive care, recognition and treatment of life-threatening complications, evaluation of response, and, finally, management of the disease in special conditions such as older patients, children and pregnant women.

Monitoring of minimal residual disease in leukemia, advantages and pitfalls

The term 'minimal residual disease' (MRD) defines the level of disease detectable in patients in clinical remission during therapy, below the detection limit of conventional methods. Very sensitive methods can be used, able to identify one leukemic cell out of 10,000 normal lymphocytes. In vivo measurements of leukemia cytoreduction reflect the combined effect of clinical and biological variables, thus providing direct information on the effectiveness of treatment in each patient. Thus, these methods can potentially be used for tailoring treatment and personalize the cure. Although MRD studies are becoming an integral part of the modern management of patients with leukemia, several parameters are critical for the application and interpretation of MRD studies, including therapeutic context, timing of sampling, target genes and sensitivity of the polymerase chain reaction (PCR) assay, inter-laboratory standardization (particularly relevant in multicenter studies), selection of patients, retrospective or prospective nature of the study. Methodologies and pitfalls as well as results of clinical uses of MRD will be reviewed in this article by selecting significant examples of its clinical impact in the management of patients with leukemia.

Treatment of acute promyelocytic leukemia with arsenic trioxide without ATRA and/or chemotherapy

INTRODUCTION

Arsenic trioxide is effective and approved for treatment of relapsed or refractory acute promyelocytic leukemia (APL) cases resistant to all-trans retinoic acid (ATRA), but its effect on new cases of APL is not clear.

MATERIALS AND METHODS

We studied 111 patients with APL. Arsenic trioxide was infused at 0.15 mg/kg daily dose, until complete remission was achieved. Then, after 28 days of rest, arsenic trioxide was infused daily for 28 days as consolidation therapy. We studied minimal residual disease (MRD) by semi-sensitive reverse transcription polymerase chain reaction (RT-PCR) on peripheral blood samples.

RESULTS

Complete remission was observed in 95 patients (85.6%). With the median (range) follow-up period of 16.5 (1-57) months, 1- and 2-year disease-free survival was 88.3% and 63.7%, respectively; 24 patients relapsed, 19 of whom achieved a second complete remission, again by arsenic trioxide. Third and fourth remissions were seen in some relapsed patients, again by arsenic trioxide. For patients in complete remission, 1- and 3-year survival was 95.5% and 87.6%, respectively. MRD was positive in four (8.3%) out of 48 cases during 1 year after remission induction; three of them relapsed clinically.

CONCLUSIONS

Arsenic trioxide is effective as first-line treatment for APL. Results of arsenic trioxide combination therapy with chemotherapy/ATRA requires further study.