Extramedullary disease in acute promyelocytic leukemia

Diagnosis and management of acute promyelocytic leukemia: Brazilian consensus guidelines 2024 on behalf of the Brazilian Association of Hematology, Hemotherapy and Cellular Therapy

Improvements in clinical assessment have occurred since the last published recommendations on the diagnosis and treatment of acute promyelocytic leukemia in 2013. Here, a committee of specialists of the Brazilian Association of Hematology, Hemotherapy and Cellular Therapy presents a comprehensive review on the current knowledge, focusing on the advances in diagnosis, risk assessment, and frontline and salvage therapy. The concept of urgent diagnosis is explored as well as the management of critical situations such as coagulopathy and differentiation syndrome. Recent adjustments in risk stratification based on white blood cell counts only are presented together with the incorporation of chemo-free regimens for non-high-risk patients. Special conditions such as acute promyelocytic leukemia in children, the elderly and pregnant women are discussed. Finally, acute promyelocytic leukemia is presented as a highly curable disease because of the real possibility of targeted therapy towards differentiation, and, paradoxically, as a serious and urgent condition that deserves prompt recognition and management to avoid early mortality.

Epidemiology and early mortality patterns of acute promyelocytic leukemia in the United States

There is a lack of contemporary population-based data on the epidemiology of acute promyelocytic leukemia (APL) in the United States. In this study, we aim to elucidate the demographics and early mortality patterns of APL hospitalizations utilizing the National Inpatient Sample database from 2016-2019. APL's annual age-adjusted incidence rate was 0.28/100,000, and the incidence increased with age, with the peak incidence in the 75-79 age group at 0.62/100,000. Whites constituted the majority of admissions at 67.7%, followed by Hispanics at 15.3%, the youngest racial group with a median age of 40 years. The median length of stay was 31 days for patients age < 60 years and 25 days for age ≥ 60 years (p < 0.001). After adjusting for confounders, the mean length of stay was 7 days higher in teaching hospitals compared to non-teaching hospitals (p 0.001). Overall mortality was 12.1% (22.2% for age ≥ 60 and 6.4% for < 60 years {p < 0.001}), and 56.5% of deaths happened before 7 days, with the median time to death being 6 days. The proportion of early deaths (< 7 days) in non-teaching hospitals was higher than late deaths (≥ 7 days) (19.2% vs. 5%; p 0.03), and admission to a teaching hospital was associated with lower mortality (adjusted odds ratio 0.27; p 0.01). Therefore, optimal treatment strategies need to be explored to mitigate this significant early mortality, especially in non-teaching hospitals.

Case Report: Very Late, Atypical Extra-Medullary Relapse in a Patient With Acute Promyelocytic Leukemia (APL) Rescued With a Transplant-Free Approach

Relapses of acute promyelocytic leukemia (APL) beyond 7 years from the first molecular remission are exceptional, and it is unclear whether these relapses represent a new, therapy-related leukemia rather than a delayed relapse of the original leukemic clone. The increase extra-medullary relapses (ER) in the era of all-trans retinoic acid (ATRA) therapy suggests a potential correlation between ATRA therapy and ER, and several potential explanations have been proposed. The gold standard post-remission approach, particularly for patients in late relapse, has not yet been established. The benefit of a transplant approach has been questioned in this setting because continuing ATRA-arsenic trioxide (ATO) might be curative. Here we report on the case of an APL patient who relapsed 9 years after achieving her first molecular complete remission (mCR) and who showed an atypical isolated localization at nodal sites, including the into- and peri-parotid glands. Genomic PML/RARa breakpoint analysis detected the same bcr3 PML/RARa hybrid gene in DNA purified from bone marrow and lymph nodes, suggesting that the relapse was because of the reemergence of the initial clone. This case shows that APL, treated with ATRA and cytotoxic drugs, may still emerge in extra-medullary sites even after a very prolonged mCR and could be salvaged with an ATO-based protocol, not including a transplant approach.

Diagnostic and Therapeutic Considerations for Extramedullary Leukemia

PURPOSE OF REVIEW

The purpose of this review is to summarize the current literature on the presentation, diagnosis, and treatment options available for extramedullary (EM) manifestations of leukemia including myeloid sarcoma (MS) and leukemia cutis (LC).

RECENT FINDINGS

Advanced imaging using 18FDG-PET/CT is an effective screening tool for EM manifestations of leukemia. The role of radiation therapy has been more clearly delineated in the treatment of both MS and LC. FDA-approved targeted agents have improved outcomes in patients with AML but have not demonstrated improvements specifically for EM; however, a checkpoint inhibitor, Ipilimumab, holds promise in impacting local control for the treatment of AML-related EM. EM manifestations of leukemia pose significant therapeutic challenges. Treatment of EM is predicated on multiple factors including the presence of concomitant bone marrow involvement, AML-risk classification, and timing of presentation at initial diagnosis or relapse following systemic therapy.

A unique clinical presentation of de novo acute promyelocytic leukemia as a myeloid sarcoma of the breast

Myeloid sarcoma is a rare presentation of acute leukemia as a solid tumor at various extramedullary sites. It may present concurrently, before or after the onset of systemic bone marrow leukemia. Unusual clinical localization may lead to misdiagnosis, or delayed diagnosis and treatment. We describe the first case, to our knowledge, of de novo myeloid sarcoma of the breast confirmed as acute promyelocytic leukemia. Immunohistochemical analysis, flow cytometry, fluorescent in situ hybridization analysis and molecular analysis using RQ-PCR of tissue samples should be routine in determining the correct diagnosis in this setting.

Promyelocytic sarcoma of the right humerus: an unusual clinical presentation with unique diagnostic and treatment considerations

Promyelocytic leukemia is a known medical emergency and requires rapid diagnosis and expedient therapy with differentiating agents. We present an unusual case in which the diagnosis is based on a fine needle aspirate of a humeral mass. Despite lack of systemic involvement, the sarcoma responded to traditional differentiation agents.

Recent advances in acute promyelocytic leukaemia

Acute promyelocytic leukaemia (APML) is a subtype of leukaemia arising from a distinct reciprocal translocation involving chromosomes 15 and 17, which results in the PML-RARA fusion gene. Over the past three decades, APML has been transformed from a highly fatal disease to a highly curable one. This drastic improvement is because of the introduction of a new treatment strategy with all-trans retinoic acid and, more recently, arsenic trioxide. The revolutionary treatment of APML has also paved the way for a new cancer treatment, which is genetically targeted therapy. In this review, we look into this amazing journey of transformation and provide recent advances in the management of APML.

Mixed Phenotypic Acute Leukemia (mixed myeloid/B-cell) with Myeloid Sarcoma of the Thyroid Gland: A Rare Entity with Rarer Asssociation - Detected on FDG PET/CT

Mixed phenotypic acute leukemia (MPAL) is a rare clinical entity. MPAL associated with myeloidsarcoma (MS) is still rarer with only three cases mentioned in English literature. MS has been described in myriads of location, most commonly in skin, gums and lymph nodes. Although theoritically possible, it is very rare to find MS involving the thyroid gland. The diagnosis of MS can be elusive, very often masquerades and mislabeled as lymphoma. A high index of clinical suspicion coupled with PET/CT findings along with morphological clues and thorough peripheral blood, and bone marrow evaluation is mandatory for arriving at the definitive diagnosis. We report the case of a 58-year-old female presenting with thyroid swelling that was subsequently diagnosed to be MS of the thyroid with underlying MPAL (mixed myeloid/B-cell) only after ¹⁸F-FDG PET/CT, which revealed an unusual abnormal pattern of multifocal intense FDG uptake in the thyroid gland.

Retinoic acid syndrome after one dose of all-transretinoic acid

All-trans-retinoic acid (ATRA) is typically used as a first line agent in the treatment of acute promyelocytic leukaemia (APL), achieving complete remission (CR) rates (incombination with chemotherapy) of about 90%. One of the drawbacks of the use of ATRA is that up to 30% of patients can present with retinoic acid syndrome (RAS), which can be fatal in some patients. We describe a case of RAS after only one dose of ATRA, which to our knowledge has not previously been identified in the literature. The pathophysiology and treatment of APL is presented. A clinical description of RAS is outlined, and an evaluation of risk factors for developing RAS is reviewed.

Central nervous system prophylaxis in diffuse large B-cell lymphoma

Central nervous system (CNS) involvement with diffuse large B-cell lymphoma (DLBCL) is a relatively uncommon manifestation; with most cases of CNS involvement occuring during relapse after primary therapy. CNS dissemination typically occurs early in the disease course and is most likely present subclinically at the time of diagnosis in many patients who later relapse in the CNS. CNS relapse in these patients is associated with poor outcomes. Based on a CNS relapse rate of 5% in DLBCL and weighing the benefits against the toxicities, universal application of CNS prophylaxis is not justified. The introduction of rituximab has significantly reduced the incidence of CNS relapse in DLBCL. Different studies have employed other agents for CNS prophylaxis, such as intrathecal chemotherapy and high-dose systemic agents with sufficient CNS penetration. If CNS prophylaxis is to be given, it should be preferably administered during primary chemotherapy. However, there is no strong evidence that supports any single approach for CNS prophylaxis. In this review, we outline different strategies of administering CNS prophylaxis in DLBCL patients reported in literature and discuss their advantages and drawbacks.

Cerebrospinal fluid involvement in acute promyelocytic leukaemia at presentation

In acute promyelocytic leukaemia (APL), extramedullary disease (EMD) is rare but can occur in those who relapse following therapy. Although the most common site of EMD in APL is central nervous system (CNS) and skin, CNS involvement in recently diagnosed patients with APL is very rare and rarely described. We report cerebrospinal fluid involvement in a case of APL, on day 3 of induction therapy.

Extramedullary disease in APL: a real phenomenon to contend with or not?

In the last 2 decades an increasing number of patients reported with extramedullary involvement among relapsed acute promyelocytic leukemia (APL) patients. Several investigators related this phenomenon to the relatively new treatment of all-trans-retinoic-acid (ATRA). In this review article we will examine what has been reported in the medical literature on extramedullary disease in APL: the common sites to be involved, the clinical risk factors to its development, the role of ATRA and arsenic tri-oxide and the recommended treatment.

Leptomeningeal Relapse of Acute Promyelocytic Leukemia

Extramedullary relapse (EMR) of acute promyelocytic leukemia (APL) is a rare entity, with predilection to involve the central nervous system (CNS). Risk factors include leukocytosis of > 10 × 10⁹/L, bcr3 isoform, microgranular variant, age > 45 years and development of subarachnoid hemorrhage (SAH) during induction therapy. We report a case of APL who completed induction and consolidation therapy but subsequently relapsed with leptomeningeal involvement. Retrospectively, we identified several risk factors for EMR in our patient. Interestingly, the use of all-trans retinoic acid has recently been associated with higher risk of EMR possibly due to up-regulation of adhesion molecules on the surface of the leukemic cell, resulting in their passage through the endothelium to extramedullary tissues. However, data remain conflicting in that regard. Although universal CNS prophylaxis has been suggested, the low incidence of EMR among APL patients renders this strategy less attractive. Nonetheless, active surveillance and CNS prophylaxis may be considered in patients at high risk for EMR, particularly in those of SAH during induction therapy. Further research is needed to evaluate the effectiveness and safety of this strategy.

Troxacitabine Activity in Extramedullary Myeloid Leukemia

Troxacitabine is a novel L-enantiomer nucleoside analog with unique properties in terms of its structure, pharmacokinetics, intracellular transport, and susceptibility to mechanisms of resistance. Troxacitabine has significant activity in patients with refractory myeloid leukemias, both as a single agent and when combined with standard anti-leukemia agents. In a cohort of 170 patients with refractory myeloid leukemia treated with troxacitabine-based regimens on Phase 1 or 2 studies, 10 (6%) had biopsy-proven extramedullary disease, either with or without bone marrow involvement. Six of these patients who received single-agent troxacitabine, 4 received a combination of troxacitabine and cytarabine. Complete response and disappearance of all extramedullary lesions were observed in 6 (60%) of these 10 patients. Two of the 6 responding patients relapsed within 3 months, 2 patients had remissions of 8 and 9 months duration, respectively, 1 patient is in on-going remission at 3, and 1 patient is lost to follow-up. Troxacitabine-based therapy had significant antileukemic activity in extramedullary myeloid leukemias and warrants further investigation in this clinical situation.

Acute promyelocytic leukemia presenting as an extradural mass

Acute promyelocytic leukemia is potentially a highly curable type of leukemia that usually presents with pancytopenia, coagulopathies and bleeding. We describe a case of an unusual presentation of acute promyelocytic leukemia. A 53 year-old male was admitted complaining of pain and weakness in his legs. He presented at examination a spastic paraparesis with a sensitive level at the eighth thoracic medullar (T8) segment. Magnetic resonance imaging showed a posterolateral extradural mass from T6 through T8 segments with medullar compression. A complete blood count showed anemia, thrombocytopenia and the presence of promyelocytes and blasts. Marrow examination was compatible with the diagnosis of acute promyelocytic leukemia by cytogenetics and polymerase chain reaction for the PML-RARα gene. He was treated with all-trans-retinoic acid therapy plus daunorubicin and presented an all-trans-retinoic acid syndrome. Despite hematological remission, the patient presented neurologic deterioration and had to be treated with radiotherapy (total dose 3000 cGy) of the extradural lesion. The patient evolved with severe sepsis and died without any recovery from his neurologic deficit. Extramedullary infiltration is a very rare complication in acute promyelocytic leukemia. Most cases are related to relapse after initial treatment with all-trans-retinoic acid. The skin and the central nervous system are the most frequently involved sites. This is possibly the first case reported of this condition in which the patient had a symptomatic extradural mass.

Emerging new approaches for the treatment of acute promyelocytic leukemia

The introduction of all-trans retinoic acid (ATRA) in the late 1980s combined with anthracycline-based chemotherapy has revolutionized the prognosis of acute promyelocytic leukemia (APL) with more than 90% complete response rates and cure rates of approximately 80%. The subsequent advent of arsenic trioxide (ATO) in 1990s and progress in the treatment of APL have changed its course from a highly fatal to a highly curable disease. Despite the dramatic improvement in clinical outcome of APL, treatment failure still occurs due most often to early death. Relapse has become increasingly less frequent, most commonly occurring in patients with high-risk disease. A major focus of research for the past decade has been to develop risk-adapted and rationally targeted nonchemotherapy treatment strategies to reduce treatment-related morbidity and mortality to low- and intermediate-risk or older patients while targeting more intensive or alternative therapy to those patients at most risk of relapse. In this review, emerging new approaches to APL treatment with special emhasis on strategies to reduce early deaths, risk-adapted therapy during induction, consolidation and maintenance, as well as an overview of current and future clinical trials in APL will be discussed.

Myeloid sarcoma: an unusual presentation of acute promyelocytic leukemia causing spinal cord compression

Acute promyelocytic leukemia with concurrent myeloid sarcoma is a rare clinical event. Herein we describe a patient that presented with back pain and bilateral leg weakness caused by spinal cord compression due to extramedullary deposition of leukemic cells. Acute promyelocytic leukemia was suspected based on immunophenotypic findings of malignant cells in bone marrow aspirate. The diagnosis was confirmed by the presence of PML-RARα fusion copies. MRI showed multiple hyperintense changes on the vertebral bodies, together with intraspinal masses causing spinal cord compression. The patient immediately underwent radiotherapy, and was treated with all-trans retinoic acid and idarubicin. Reassessment MRI showed complete resolution of all intraspinal masses and the disappearance of most of the bony lesions. Post-treatment bone marrow aspirate showed complete hematological and molecular remission. The motor power of his legs fully recovered from 0/5 to 5/5; however, sensory loss below the T4 level persisted.

Extramedullary disease in acute promyelocytic leukemia: two-in-one disease

In acute promyelocytic leukemia (APL), extramedullary disease (EMD) is particularly rare and shows special clinical and biological features. It is estimated that about 3-5% of APL patients will suffer extramedullary relapse. The most common site of EMD in APL is the central nervous system (CNS). At present, there are still many issues of EMD in APL needing further clarification, including pathogenesis, risk factors, prognosis and treatment. A better understanding of the biological mechanisms underlying EMD is important to be able to devise more effective CNS prophylaxis and induction-consolidation therapeutic strategies.

Acute promyelocytic leukemia: an experience on 95 greek patients treated in the all-trans-retinoic Acid era

Acute promyelocytic leukemia (APL) is highly curable with the combination of all-transretinoic acid (ATRA) and anthracycline based chemotherapy, but the percentage of early deaths remains high. In the present study, we report the clinical, immunophenotypic, cytogenetic and molecular characteristics and outcome of APL patients diagnosed and treated in various Hospitals of Greece and Cyprus.We describe the data of ninety-five APL patients who were diagnosed during the last 15 years. Seven (7.4%) newly diagnosed APL patients died due to intracranial hemorrhage within 72 hours of presentation. All but two patients were induced with ATRA alone or ATRA plus chemotherapy. The early death rate was 14.9%. After induction all 80 evaluable patients achieved complete hematologic remission. The cumulative incidence of relapse was 18.3%. Eight of the ten relapsed patients were successfully salvaged, while both patients with molecularly resistant disease died during salvage treatment. Overall survival (OS) at 5 years was 78.4% and disease free survival (DFS) 73.6%. In multivariate analysis of OS age over 60 years, DIC at diagnosis and marginally major hemorrhage at presentation were identified as adverse prognostic factors. In the subgroup of patients with available data on FLT3 mutation status (49 out of 94), ITD positivity also remained as an independent prognostic factor in the final model of OS, together with major hemorrhage and marginally high Sanz score. We found a close correlation between the CD2 expression and the development of the differentiation syndrome (DS). In conclusion, the main problem in managing patients with APL is still the high early death rate.

How I treat extramedullary acute myeloid leukemia

Extramedullary (EM) manifestations of acute leukemia include a wide variety of clinically significant phenomena that often pose therapeutic dilemmas. Myeloid sarcoma (MS) and leukemia cutis (LC) represent 2 well-known EM manifestations with a range of clinical presentations. MS (also known as granulocytic sarcoma or chloroma) is a rare EM tumor of immature myeloid cells. LC specifically refers to the infiltration of the epidermis, dermis, or subcutis by neoplastic leukocytes (leukemia cells), resulting in clinically identifiable cutaneous lesions. The molecular mechanisms underlying EM involvement are not well defined, but recent immunophenotyping, cytogenetic, and molecular analysis are beginning to provide some understanding. Certain cytogenetic abnormalities are associated with increased risk of EM involvement, potentially through altering tissue-homing pathways. The prognostic significance of EM involvement is not fully understood. Therefore, it has been difficult to define the optimal treatment of patients with MS or LC. The timing of EM development at presentation versus relapse, involvement of the marrow, and AML risk classification help to determine our approach to treatment of EM disease.

Acute promyelocytic leukemia presenting with central nervous system involvement: a report of 2 cases

Central nervous system (CNS) involvement in acute promyelocytic leukemia (APL) is rare, and the presence of CNS symptoms at the time of diagnosis of APL is even rarer. We report 2 cases of APL presenting with CNS involvement. A 43-yr-old woman presented with easy bruising and stuporous mentality. Her complete blood count (CBC) revealed leukocytosis with increased blasts. Bone marrow (BM) analysis was carried out, and the diagnosis of APL was confirmed. This was done by cytogenetic analysis and demonstration of PML-RARα rearrangement by reverse transcriptase PCR in the BM cells. A lumbar puncture was performed to investigate the cause of her stuporous mentality, and her cerebrospinal fluid (CSF) analysis revealed 97% leukemic promyelocytes. Despite systemic and CNS therapy, she died due to septic shock by infection and rapid disease progression only 3 days after her admission. Another patient, a 3-yr-old girl, presented with easy bruising and epistaxis, and her CBC showed pancytopenia with increased blasts. BM studies confirmed APL. Quantitative PCR for PML-RARα in the BM cells revealed a PML-RARα/ABL ratio of 0.33 and CSF analysis revealed 9.5% leukemic promyelocytes (2 of 21 cells). She received induction chemotherapy and intrathecal therapy and achieved complete remission (CR) in the BM and CNS. She has been maintained in the CR status for the past 31 months. Thus, patients with APL must be evaluated for CNS involvement if any neurological symptoms are present at the time of diagnosis.

Promyelocytic sarcoma of the spine: a case report and review of the literature

Myeloid sarcoma (MS, previously named granulocytic sarcoma or chloroma) is a rare extramedullary tumour of immature myeloid cells. It can be present before, concurrently with, or after the diagnosis of acute myeloid leukemia. MS is extremely uncommon in acute promyelocytic leukemia (APL). In the case described here, MS was the sole site of APL relapse and the cause of spinal cord compression. The patient presented with neurologic symptoms due to a paravertebral mass of MS after 7 years of complete remission. He was treated with excision of the mass followed by local radiotherapy. Systemic treatment was also given with combined arsenic trioxide and all-trans retinoic acid and the patient was able to achieve a second prolonged clinical and molecular remission.

Acute promyelocytic leukemia at time of relapse commonly demonstrates cytogenetic evidence of clonal evolution and variability in blast immunophenotypic features

Despite the success of the current therapy for patients with acute promyelocytic leukemia (APL), relapse occurs in up to 30% of patients. The characteristics of relapsed APL are not well described. We evaluated a group of APL cases at relapse and compared the clinicopathologic, immunophenotypic, molecular, and cytogenetic findings with those at initial diagnosis. From a group of 207 patients with APL, in 38 patients morphologic evidence of relapse developed. In 30 patients relapse was isolated to bone marrow, and 8 had extramedullary disease. Blasts were morphologically stable in 37 patients. Changes in the immunophenotypic profile were common, the most frequent being gain of CD34, HLA-DR, or CD33 and attenuation or loss of CD13. Cytogenetic changes were common at relapse. The size of the PML-RARalpha fusion transcript was invariable. We conclude that changes in the immunophenotype and cytogenetic evidence of clonal evolution are common in APL at the time of relapse.

Central nervous system involvement at first relapse in patients with acute promyelocytic leukemia treated with all-trans retinoic acid and anthracycline monochemotherapy without intrathecal prophylaxis

BACKGROUND

The prevalence of and risk factors for central nervous system recurrence in patients with acute promyelocytic leukemia are not well established and remain a controversial matter.

DESIGN AND METHODS

Between 1996 and 2005, 739 patients with newly diagnosed acute promyelocytic leukemia enrolled in two consecutive trials (PETHEMA LPA96 and LPA99) received induction therapy with all-trans retinoic acid and idarubicin. Consolidation therapy comprised three courses of anthracycline monochemotherapy (LPA96), with all-trans retinoic acid and reinforced doses of idarubicin in patients with an intermediate or high risk of relapse (LPA99). Central nervous system prophylaxis was not given.

RESULTS

Central nervous system relapse was documented in 11 patients. The 5-year cumulative incidence of central nervous system relapse was 1.7% (LPA96 3.2% and LPA99 1.2%; p=0.09). The cumulative incidence was 0%, 0.8%, and 5.5% in low-, intermediate-, and high-risk patients, respectively. Relapse risk score (p=0.0001) and the occurrence of central nervous system hemorrhage during induction (5-year cumulative incidence 18.7%, p=0.006) were independent risk factors for central nervous system relapse.

CONCLUSIONS

This study shows a low incidence of central nervous system relapse in patients with acute promyelocytic leukemia following therapy with all-trans retinoic acid and anthracycline without specific central nervous system prophylaxis. Central nervous system relapse was significantly associated with high white blood cell counts and prior central nervous system hemorrhage, which emerged as independent prognostic factors.

Incidence of extramedullary disease in patients with acute promyelocytic leukemia: a single-institution experience

Using current treatment regimens, over 90% of patients with acute promyelocytic leukemia will achieve complete remission (CR). However, approximately 30% of these patients will relapse, including a small proportion who will develop extramedullary disease (EMD). In this study, we investigated the incidence of EMD in 263 patients with APL who were treated at our institution from January 1990 to May 2008. With a median follow-up of 31 months (range 2 days-203 months), 8 (3%) patients developed EMD. The most commonly affected site was the central nervous system (n = 7). Before developing EMD, one patient had achieved CR with a chemotherapy-only regimen, six patients had achieved CR with all-trans-retinoic acid (ATRA)-based regimens, and one patient had achieved CR with an ATRA plus arsenic trioxide (ATO)-based regimen. The EMD conferred a poor prognosis; five patients died within 4 months of developing EMD. The molecular status did not predict EMD; four patients had a negative PCR for the PML-RARA transcripts prior to relapse with EMD. In conclusion, the incidence of EMD is low. We were unable to identify any specific factors that could predict the development of EMD.

Isolated central nervous system recurrence of acute promyelocytic leukemia in children

The incidence of isolated central nervous system (iCNS) relapse in pediatric acute promyelocytic leukemia (APL) is debated. We analyzed the literature, focusing on clinical trials reported since the advent of ATRA use. Only 2/218 (0.92%) good risk patients (diagnostic WBC <10,000/microl) had truly iCNS relapse. This incidence does not support the use of intrathecal CNS prophylaxis for all children with APL. We also identified multiple deficiencies in these reports. Additional reporting of these events could provide insight into the true incidence and pathogenesis of iCNS relapse and might allow for identification of risk factors associated with such extramedullary relapse.

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.

Acute promyelocytic leukemic involvement of the optic nerves following mitoxantrone treatment for multiple sclerosis

Mitoxantrone, the first immunosuppressant to receive FDA approval for treatment of worsening relapsing-remitting, secondary progressive, and progressive-relapsing multiple sclerosis (MS) is a DNA topoisomerase II inhibitor that has been associated with the development of acute promyelocytic myelogenous leukemia (APML). Central nervous system APML is a rare site of extramedullary involvement following mitoxantrone therapy. We report a patient with history of multiple sclerosis who developed bilateral optic nerve involvement as the primary manifestation of APML relapse following mitoxantrone treatment.

Isolated central nervous system relapse in childhood acute promyelocytic leukemia

Central nervous system (CNS) involvement is rare in acute promyelocytic leukemia (APL). The majority of CNS relapses occur in patients with hyperleukocytosis at presentation, and the optimal management of such patients is still controversial. We describe a 13-year-old boy with APL who developed an isolated CNS relapse after first-line treatment with all-trans retinoic acid and chemotherapy. A second remission was achieved with a regimen consisting of intrathecal chemotherapy, intravenous high-dose cytarabine, and oral 6-mercaptopurine. All-trans retinoic acid was avoided owing to severe complications during initial therapy. The patient remains in molecular remission at 9 months after autologous stem cell transplant. Prognostic factors of CNS relapse in children with APL are needed to define the indications for CNS prophylaxis in this group of patients.

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.

Extramedullary disease and targeted therapies for hematological malignancies—is the association real?

During the past years targeted therapies have gained a major role in the treatment of cancer patients, including those with hematological malignancies. Extramedullary involvement is a rare manifestation of acute and chronic leukemias and of multiple myeloma. Nevertheless, with the expanding use of targeted treatments there is an impression that the incidence of extramedullary relapses is increasing. We reviewed the reports on this phenomenon in patients treated with all-trans-retinoic acid and arsenic trioxide for acute promyelocytic leukemia, thalidomide and bortezomib for multiple myeloma and imatinib for chronic myeloid leukemia. The pathogenetic mechanisms suggested are: life prolongation by these treatments allowing for disease progression arising from dormant cells; poor penetration of the drugs to sanctuary sites like the central nervous system; the requirement of some of these drugs, especially thalidomide, for the marrow microenvironment to exert their action; and finally, a possible active role for some of the drugs, like all-trans-retinoic acid. Since the use of these targeted therapies is expanding we should be aware of this association.

Extramedullary relapse in acute promyelocytic leukemia treated with all-trans retinoic acid and chemotherapy

We analyzed the incidence, presenting features, risk factors of extramedullary (EM) relapse occurring in acute promyelocytic leukemia (APL) treated with all-trans retinoic acid (ATRA) and chemotherapy by using a competing-risk method. In total, 740/ 806 (92%) patients included in three multicenter trials (APL91, APL93 trials and PETHEMA 96) achieved CR, of whom 169 (23%) relapsed, including 10 EM relapses. Nine relapses involved the central nervous system (CNS) and one the skin, of which two were isolated EM relapse. In patients with EM disease, median WBC count was 26950/mm3 (7700-162000). The 3-year cumulative incidence of EM disease at first relapse was 5.0%. Univariate analysis identified age <45 years (P=0.05), bcr3 PML-RARalpha isoform (P= 0.0003) and high WBC counts (> or = 10,000/ mm3) (P<0.0001) as risk factors for EM relapse. In multivariate analysis, only high WBC count remained significant (P= 0.001). Patients with EM relapse had a poorer outcome since median survival from EM relapse was 6.7 months as compared to 26.3 months for isolated BM relapse (P=0.04). In conclusion, EM relapse in APL occurs more frequently in patients with increased WBC counts (> or = 10,000/mm3) and carries a poor prognosis. Whether CNS prophylaxis should be systematically performed in patients with WBC > or = 10,000/mm3 at diagnosis remains to be established.

Recurrent extramedullary relapse of acute promyelocytic leukemia after allogeneic stem cell transplantation: successful treatment by arsenic trioxide in combination with local radiotherapy

Isolated extramedullary relapse is rare in patients with acute promyelocytic leukemia (APL) after allogeneic stem cell transplantation (SCT), and an optimal therapy for it has not been established. We describe a patient with APL who developed serially occurring extramedullary disease (EMD) after SCT. We confirmed that EMD had arisen from the recipient's APL blasts by detecting t(15;17) and PML/RARalpha from the tumor cell suspension. The patient displayed EMD 4 times at different sites. Administration of all-trans retinoic acid with local radiotherapy and with chemotherapy for the first to third EMDs resulted in regression of the tumors. However, these regimens did not prevent the subsequent occurrence of new EMD. For the fourth EMD, intravenous administration of arsenic trioxide followed by local radiotherapy resulted in the disappearance of EMD, and no further EMD has developed to date. In the present case, the bone marrow was in morphologic and molecular remission during the course of recurrent EMD. The accumulation of detailed cases is needed to elucidate the pathogenesis, predisposing factors, and optimal therapy for EMD in APL after SCT.

Acute myelogenous leukemia--microenvironment interactions: role of endothelial cells and proteasome inhibition

How leukemia progenitors interact with marrow microenvironment components is poorly understood. In this work, the effects of endothelial coculture on acute myelogenous leukemia (AML) blast survival is examined as are the effects of endothelial coculture on the impact of a cytotoxic agent such as cytarabine. Similar to marrow stromal cells, endothelial cells are able to increase survival and proliferation of AML blasts and to partially protect against cytarabine effects. The proteasome inhibitor, bortezomib, has inhibitory effects in multiple myeloma in part through effects on marrow stromal cells. Bortezomib has been found to inhibit AML blast survival. Such inhibition is less, however, in the presence of endothelial monolayers. Furthermore, AML blast transmigration through human umbilical vein endothelial cells is inhibited by bortezomib. These studies demonstrate that AML is subject to influence of endothelial cells and of agents such as bortezomib which have potential impact on AML interaction with the microenvironmental niche.

Meningeal relapse in a patient with acute promyelocytic leukemia: a case report and review of the literature

The involvement of central nervous system is rare in acute promyelocytic leukemia (APL). We report a APL patient of a 41 yr-old Korean male who presented with fever and petechia. Complete molecular remission was achieved with all-trans retinoic acid (ATRA), idarubicin, and cytarabine. Ten months later, he complained of a mild headache. The results of the physical examination and the complete blood counts were normal. The examination of cerebrospinal fluid showed the presence of promyelocyte. Bone marrow studies showed cytogenetic remission but with molecular relapse. He was treated with intrathecal and systemic chemotherapy.

Long-term follow-up and potential for cure in acute promyelocytic leukaemia

Acute promyelocytic leukaemia (APL) may be characterized simultaneously as the most potentially rapidly fatal human acute leukaemia if untreated, yet the most frequently cured acute leukaemia if promptly diagnosed and treated without delay. Co-operative group and single-institution studies which include large numbers of patients with relatively long follow-up demonstrate that, with all-trans retinoic acid (ATRA) plus anthracycline-based chemotherapy, the majority of newly-diagnosed patients appear cured of their disease. The 5-year disease-free survival rates range from 75 to 85%. Early death is still observed in approximately 10% of patients and remains a difficult obstacle to increasing the cure rate. Prognostic factors which identify patients at high risk for recurrence are becoming increasingly recognized. Older age (over age 55-60 years), elevated white blood cell count at presentation (higher than 5,000-10,000/microl), and expression of CD56 unfavourably influence outcome. The treatment of such patients remains a challenge, although it is important to note that APL is the only type of AML in which a significant proportion of older patients may be cured. Because more patients are cured of their disease, potential long-term consequences may become increasingly recognized. These include the emergence of extramedullary disease, the development of secondary myelodysplasia or acute myeloid leukaemia and the potential for late-onset cardiac toxicity.

Acute promyelocytic leukaemia:a review

Acute promyelocytic leukaemia (APL) is characterised by the fusion gene transcript PML-RAR-alpha and is now the most frequently curable acute leukaemia in adults if promptly diagnosed and adequately treated. The clinical presentation is associated with a haemorrhagic diathesis and the blasts almost always have Auer rods. Poor prognostic factors include older age, elevated white blood cell count, low platelet count, and CD56 expression. The introduction of all-trans retinoic acid (ATRA), which leads to the differentiation of leukaemic blasts into mature granulocytes has been the major breakthrough in the treatment of APL. Induction treatment with concurrent ATRA and chemotherapy leads to a rapid resolution of the characteristic life-threatening coagulopathy, high complete remission rates and excellent survival rates, compared to chemotherapy alone. However, treatment with ATRA is associated with the retinoic acid syndrome (RAS), which is a major toxicity and may lead to mortality. The role of cytarabine as a part of initial induction regimen remains unclear. After achievement of complete remission (CR), there is a definitive role of maintenance therapy with ATRA with or without low-dose chemotherapy. In relapsed patients, arsenic trioxide is considered the treatment of choice. However, the best postremission treatment for patients with second CR remains unknown. With the continued improvement in the field of stem cell transplantation, it may play an important role in the few patients with relapsed/refractory disease or those in second CR.

The molecular pathogenesis of acute promyelocytic leukaemia: implications for the clinical management of the disease

Acute promyelocytic leukaemia (APL) is characterised by chromosomal rearrangements of 17q21, leading to fusion of the gene encoding retinoic acid receptor alpha (RARalpha) to a number of alternative partner genes (X), the most frequent of which are PML (>95%), PLZF (0.8%) and NPM (0.5%). Over the last few years, it has been established that the X-RARalpha fusion proteins play a key role in the pathogenesis of APL through recruitment of co-repressors and the histone deacetylase (HDAC)-complex to repress genes implicated in myeloid differentiation. Paradoxically, the X-RARalpha fusion protein has the potential to mediate myeloid differentiation at pharmacological doses of its ligand (all trans-retinoic acid (ATRA)), which is dependent on the dissociation of the HDAC/co-repressor complex. Arsenic compounds have also been shown to be promising therapeutic agents, leading to differentiation and apoptosis of APL blasts. It is now apparent that the nature of the RARalpha-fusion partner is a critical determinant of response to ATRA and arsenic, underlining the importance of cytogenetic and molecular characterisation of patients with suspected APL to determine the most appropriate treatment approach. Standard protocols involving ATRA combined with anthracycline-based chemotherapy, lead to cure of approximately 70% patients with PML-RARalpha-associated APL. Patients at high risk of relapse can be identified by minimal residual disease monitoring. The challenge for future studies is to improve complete remission rates through reduction of induction deaths, particularly due to haemorrhage, identification of patients at high risk of relapse who would benefit from additional therapy, and identification of a favourable-risk group, for which treatment intensity could be reduced, thereby reducing risks of treatment toxicity and development of secondary leukaemia/myelodysplasia. With the advent of ATRA and arsenic, APL has already provided the first example of successful molecularly targeted therapy; it is hoped that with further understanding of the pathogenesis of the disease, the next decade will yield further improvements in the outlook for these patients.

CNS relapses of acute promyelocytic leukemia after all-trans retinoic acid

OBJECTIVE

To review the role of all-trans retinoic acid (ATRA) and arsenic trioxide in central nervous system (CNS) relapses of acute promyelocytic leukemia (APL).

CASE SUMMARY

A 69-year-old white man diagnosed with APL presented with bleeding diathesis. His molecular and cytogenetic studies were positive for promyelocytic leukemia-retinoic acid receptoralpha (PML-RARalpha) and t(15;17) transformation. Complete molecular and cytogenetic remission was achieved with ATRA, daunorubicin, and cytarabine. Within 6 months, the patient was readmitted for investigation of severe global headaches and an ataxic gait. His peripheral blood and cerebral spinal fluid were positive for PML-RARalpha fusion protein. Intrathecal chemotherapy and radiation, as well as ATRA, were the main treatment modalities provided. Molecular and cytogenetic remission was again obtained. Three months later, a second relapse occurred in the CNS and the peripheral blood.

DISCUSSION

APL is typically treated with anthacycline-based chemotherapy and ATRA. Approximately 85-95% of patients achieve complete remission (CR); however, the relapse rate has been reported to be about 30-40%. A thorough literature search (MEDLINE, EMBASE, CANCERLIT, 1966-January 2002) revealed only 54 cases of extramedullary disease, of which 35 involved the CNS.

CONCLUSIONS

The introduction of ATRA has improved patient survival dramatically. APL relapse, in general, has been in part attributable to repetitive or prolonged exposure to ATRA and the possibility of additional chromosomal changes, making the disease more refractory to treat. Given the evidence, one could argue that, with repeated ATRA treatment, CR duration may be shortened. However, limited data are available to guide the appropriate management of APL relapsed to the CNS with either ATRA, chemotherapy, or arsenic trioxide. In our opinion, treatment using arsenic trioxide is an unconventional option worthy of exploring.