Microgranular variant of acute promyelocytic leukemia in children

Disseminated intravascular coagulation in children with cancer: A systematic review

Disseminated intravascular coagulation (DIC) may complicate malignant disease. Numerous studies have investigated this association in adults, however only sparse knowledge exists on DIC in pediatric cancer patients. The objective of this article was to systematically review the literature regarding DIC in pediatric malignancies. PubMed and Embase were searched for relevant articles on January 31, 2020. In total, 6,070 articles were identified out of which 24 articles met inclusion and exclusion criteria. These were included in the qualitative synthesis. The National Institutes of Health's Quality Assessment Tools was used to assess bias in the included articles. The studies were of only moderate quality mainly based on medical charts and demonstrated high heterogeneity, especially as regards to diagnostic criteria. DIC was reported most frequently in patients with acute leukemia, particularly the subtype acute promyelocytic leukemia (APL). Standard coagulation parameters were used as diagnostic laboratory tests supporting the diagnosis of DIC. Hemorrhage was the predominant clinical manifestation, whereas thromboembolic events and organ failure were reported less frequently. Unfractionated heparin, platelet concentrate and fresh frozen plasma were the most frequently used supportive treatment agents. Hemorrhage accounted for the majority of deaths in children with acute leukemia and solid tumors. In conclusion, only a limited number of studies, being heterogenous and of moderate quality, have investigated DIC in pediatric malignancy. Notably, this entity seems to be complicated mainly by hemorrhage. High quality studies are needed to evaluate diagnosis, clinical manifestations and optimal treatment of DIC in childhood cancers.

Transcriptomic landscape of acute promyelocytic leukemia reveals aberrant surface expression of the platelet aggregation agonist Podoplanin

Acute promyelocytic leukemia (APL) is a medical emergency because of associated lethal early bleeding, a condition preventable by prompt diagnosis and therapeutic intervention. The mechanisms underlying the hemostatic anomalies of APL are not completely elucidated. RNA-sequencing-based characterization of APL (n = 30) was performed and compared to that of other acute myeloid leukemia (n = 400) samples and normal promyelocytes. Perturbations in the transcriptome of coagulation and fibrinolysis-related genes in APL extend beyond known culprits and now include Thrombin, Factor X and Urokinase Receptor. Most intriguingly, the Podoplanin (PDPN) gene, involved in platelet aggregation, is aberrantly expressed in APL promyelocytes and is the most distinctive transcript for this disease. Using an antibody panel optimized for AML diagnosis by flow cytometry, we also found that PDPN was the most specific surface marker for APL, and that all-trans retinoic acid therapy rapidly decreases its expression. Functional studies showed that engineered overexpression of this gene in human leukemic cells causes aberrant platelet binding, activation and aggregation. PDPN-expressing primary APL cells, but not PDPN-negative primary leukemias, specifically induce platelet binding, activation and aggregation. Finally, PDPN expression on leukemia cells in a xenograft model was associated with thrombocytopenia and prolonged bleeding time in vivo. Together our results suggest that PDPN may contribute to the hemostatic perturbations found in APL.

Addition of Arsenic Trioxide into Induction Regimens Could Not Accelerate Recovery of Abnormality of Coagulation and Fibrinolysis in Patients with Acute Promyelocytic Leukemia

Aim

All-trans retinoic acid combined to anthracycline-based chemotherapy is the standard regimen of acute promyelocytic leukemia. The advent of arsenic trioxide has contributed to improve the anti-leukemic efficacy in acute promyelocytic leukemia. The objectives of the current study were to evaluate if dual induction by all-trans retinoic acid and arsenic trioxide could accelerate the recovery of abnormality of coagulation and fibrinolysis in patients with acute promyelocytic leukemia.

Methods

Retrospective analysis was performed in 103 newly-diagnosed patients with acute promyelocytic leukemia. Hemostatic variables and the consumption of component blood were comparably analyzed among patients treated by different induction regimen with or without arsenic trioxide.

Results

Compared to patients with other subtypes of de novo acute myeloid leukemia, patients with acute promyelocytic leukemia had lower platelet counts and fibrinogen levels, significantly prolonged prothrombin time and elevated D-dimers (P<0.001). Acute promyelocytic leukemia patients with high or intermediate risk prognostic stratification presented lower initial fibrinogen level than that of low-risk group (P<0.05). After induction treatment, abnormal coagulation and fibrinolysis of patients with acute promyelocytic leukemia was significantly improved before day 10. The recovery of abnormal hemostatic variables (platelet, prothrombin time, fibrinogen and D-dimer) was not significantly accelerated after adding arsenic trioxide in induction regimens; and the consumption of transfused component blood (platelet and plasma) did not dramatically change either. Acute promyelocytic leukemia patients with high or intermediate risk prognostic stratification had higher platelet transfusion demands than that of low-risk group (P<0.05).

Conclusions

Unexpectedly, adding arsenic trioxide could not accelerate the recovery of abnormality of coagulation and fibrinolysis in acute promyelocytic leukemia patients who received all-trans retinoic acid combining chemotherapy.

Clinical characteristics, outcome and early induction deaths in patients with acute promyelocytic leukaemia: a five-year experience at a tertiary care centre

INTRODUCTION

Acute promyelocytic leukaemia (APL) is a distinct clinical and biological subtype of acute myeloid leukaemia. APL is notorious for causing early death during induction therapy, resulting in induction failure. The aim of our study was to report the clinical characteristics, outcome and early induction deaths with regard to patients with APL seen at our hospital.

METHODS

This was a retrospective study carried out at Aga Khan University Hospital, Karachi, Pakistan. Patients aged > 15 years diagnosed with APL within the period September 2007-September 2012 were included in the study.

RESULTS

Within the study period, 26 patients were diagnosed with APL based on morphology and the detection of t(15;17)(q24.1;q21.1) and promyelocytic leukaemia-retinoic acid receptor alpha (PML-RARA). The male to female ratio was 1:1. The median age of the patients was 41 (range 16-72) years. In all, there were 13 (50.0%) high-risk patients, and early induction death rate was 61.5%. Causes of early induction deaths (n = 16) included haemorrhage in 7 (43.8%) patients, differentiation (ATRA) syndrome in 7 (43.8%) and infection in 2 (12.5%). The survival rate among patients who survived the early period was 70% at 42 months. The relapse rate was 30%.

CONCLUSION

Early induction death rate was very high in patients with APL. The most common cause of early induction death in our study was haemorrhage. Outcome among patients with APL was found to be better among those who survived the initial period.

How I treat children and adolescents with acute promyelocytic leukaemia

Acute promyelocytic leukaemia (APL) is a rare subtype of acute myeloid leukaemia. The outcome of paediatric APL has improved substantially over the past 20 years; cure rates above 80% are expected when all-trans retinoic acid (ATRA) is given with anthracycline-based regimens. The presenting features of paediatric APL may include severe bleeding and thrombotic complications, which contribute to the high early death rate. The incidence of leucocytosis and the microgranular subtype is greater in paediatric than adult APL, and children experience greater ATRA-related toxicity. It is crucial to begin ATRA therapy and intensive platelet and fibrinogen replacement on first suspicion of APL. Recent risk-adapted therapeutic trials have shown that patients at greater risk of relapse benefit from the introduction of high-dose cytarabine during consolidation. Combination therapy with ATRA and arsenic trioxide provides very effective frontline treatment and may reduce the need for subsequent anthracycline therapy.

All-trans retinoic acid in the treatment of pediatric acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is a rare form of acute myeloid leukemia with specific epidemiological, pathogenetic and clinical features. Its frequency varies widely among nations, with a decreased incidence among 'Nordic' origin populations. The molecular hallmark of the disease is the presence of a balanced reciprocal translocation resulting in the PML/RAR-α gene fusion, which represents the target of the all-trans retinoic acid (ATRA) therapy. The introduction of ATRA in conjunction with anthracyclines marked a turning point in the treatment of APL, previously associated with a significant morbidity and mortality. Nowadays the standard front-line therapy for pediatric APL includes ATRA in every phase of the treatment, resulting in a complete remission rate of 90-95%. Here we provide an overview of the role of ATRA in the treatment of pediatric APL, summarizing the most relevant clinical results of recent decades and investigating future therapeutic perspectives for children with APL.

FLT3/ITD associated with an immature immunophenotype in PML-RARα leukemia

Acute promyelocytic leukemia (APL) is characterized by the specific PML-RARα fusion gene resulting from translocation t(15;17) (q22;q12). Internal tandem duplication (ITD) of the FLT3 gene has been observed in approximately 35% of APLs, and large-scale studies have identified the presence of ITD as an adverse prognostic factor for acute myeloblastic leukemia (AML) patients. Aberrant expressions of surface antigens, such as CD2, CD34, and CD56, have been found in APL, but the implications of this are not well understood. We investigated the incidence of the FLT3/ITD mutation and FLT3/D835 (I836) point mutation in 25 APL patients. Incidence ratios of FLT3/ITD, D835 (I836), and both FLT3/ITD and D835 (I836) were 36%, 36% and 8%, respectively. FLT3/ITD⁺ cases showed a predominance of the bcr3 isoform (P=0.008) and M3v morphology (P<0.001). We found that all FLT3/ITD⁺ cases expressed CD2 (9 of 9) more frequently than that of FLT3/ITD⁻ (1 of 16) (P<0.001), while only one of the CD2⁺ cases (1 of 10, 10%) did not harbor FLT3/ITD, and all CD2⁺CD34⁺ cases (5 of 5, 100%) harbored FLT3/ITD. In addition, quantitative polymerase chain reaction analysis showed that FLT3 mRNA was more abundantly expressed in FLT3/ITD⁺ than that in FLT3/ITD⁻ (P=0.025), while there was no difference between D835(I836) ⁺ and D835(I836)⁻ with regards to aberrant surface-antigen expression, expression levels of FLT3 mRNA, M3v morphology, and the bcr3 isoform of PML-RARα mRNA. This study demonstrates that the presence of FLT3/ITD, but not D835 (I836), is closely related to aberrant CD2 expression and high expression levels of FLT3 mRNA. Our findings also suggest that FLT3/ITD as a secondary genetic event may block differentiation at the immature stage of APL.

Bleeding and thrombosis in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) has evolved from being a deadly to a highly curable disease, due to targeted molecular therapy with all-trans retinoic acid (ATRA). As a result, the incidence of early hemorrhagic deaths for which APL is notorious has reduced to 5-10% as reported in clinical trials. These results are not replicated outside of clinical trials as is evident from recent population-based registries. High incidence of early hemorrhagic deaths remains the greatest contributor to treatment failure in this otherwise curable leukemia. Additionally, thrombosis is now being increasingly recognized in APL patients and may be associated with ATRA usage.

Pathogenesis and treatment of thrombohemorrhagic diathesis in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is a distinct subtype of myeloid leukemia characterized by t(15;17) chromosomal translocation, which involves the retinoic acid receptor-alpha (RAR-alpha). APL typically presents with a life-threatening hemorrhagic diathesis. Before the introduction of all-trans retinoic acid (ATRA) for the cure of APL, fatal hemorrhages due, at least in part, to the APL-associated coagulopathy, were a major cause of induction remission failure. The laboratory abnormalities of blood coagulation found in these patients indicate the occurrence of a hypercoagulable state. Major determinants of the coagulopathy of APL are endogenous factors expressed by the leukemic cells, including procoagulant factors, fibrinolytic proteins, and non-specific proteolytic enzymes. In addition, these cells have an increased capacity to adhere to the vascular endothelium, and to secrete inflammatory cytokines [i.e. interleukin-1beta (IL-1beta) and tumor necrosis factor (TNF-alpha)], which in turn stimulate the expression of prothrombotic activities by endothelial cells and leukocytes. ATRA can interfere with each of the principal hemostatic properties of the leukemic cell, thus reducing the APL cell procoagulant potential, in parallel to the induction of cellular differentiation. This effect occurs in vivo, in the bone marrow of APL patients receiving ATRA, and is associated with the improvement of the bleeding symptoms. Therapy with arsenic trioxide (ATO) also beneficially affects coagulation in APL. However, early deaths from bleeding still remain a major problem in APL and further research is required in this field. In this review, we will summarize our current knowledge of the pathogenesis of the APL-associated coagulopathy and will overview the therapeutic approaches for the management of this complication.

Does microgranular variant morphology of acute promyelocytic leukemia independently predict a less favorable outcome compared with classical M3 APL? A joint study of the North American Intergroup and the PETHEMA Group

Few studies have examined the outcome of large numbers of patients with the microgranular variant (M3V) of acute promyelocytic leukemia (APL) in the all-trans retinoic acid era. Here, the outcome of 155 patients treated with all-trans retinoic acid-based therapy on 3 clinical trials, North American Intergroup protocol I0129 and Programa para el Estudio de la Terapéutica en Hemopatía Maligna protocols LPA96 and LPA99, are reported. The complete remission rate for all 155 patients was 82%, compared with 89% for 748 patients with classical M3 disease. The incidence of the APL differentiation syndrome was 26%, compared with 25% for classical M3 patients, and the early death rate was 13.6% compared with 8.4% for patients with classical M3 morphology. With a median follow-up time among survivors of 7.6 years (range 3.6-14.5), the 5-year overall survival, disease-free survival, and cumulative incidence of relapse for patients with M3V were 70%, 73%, and 24%, respectively. With a median follow-up time among survivors of 7.6 years (range 0.6-14.3), the 5-year overall survival, disease-free survival, and cumulative incidence of relapse among patients with classical M3 morphology were 80% (P = .006 compared with M3V), 81% (P = .07), and 15% (P = .005), respectively. When outcomes were adjusted for the white blood cell count or the relapse risk score, none of these outcomes were significantly different between patients with M3V and classical M3 APL.

ATRA and anthracycline-based chemotherapy in the treatment of childhood acute promyelocytic leukemia (APL): A 10-year experience in Tunisia

Reports on childhood APL from developing countries are scarce. We treated 65 APL with two consecutive trials combining ATRA and chemotherapy. Twenty (30.7%) were aged less than 20 years including 11 girls and 9 boys, with a median age of 12 years. Fever at presentation (P=0.002) and variant APL (P=0.044) were more frequent in children, while there were no significant difference between children and adults for WBC count, Sanz's score distribution and additional cytogenetic abnormalities. The CR rate was 95% (19/20) in children and 80% (36/45) in adults (P=0.13). Differentiation syndrome (DS) was less often observed in children (1/20) than in adults (13/45) (P=0.031). Two children relapsed and died during salvage therapy, and 2 died in CR from infection and from cardiac failure attributed to anthracyclines, while other children remained alive in CR. With a median follow-up of 4 years, 4-year EFS was 75% in children and 71.1% in adults (P=0.57), while 4-year OS was 75% in children vs. 73.3% in adults (P=0.72). Our results suggest that, even in the absence of optimal socio-economic condition, ATRA combined with anthracycline-based chemotherapy gives adequate results in childhood APL, as in adults.

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.

Treatment with all-trans retinoic acid and anthracycline monochemotherapy for children with acute promyelocytic leukemia: a multicenter study by the PETHEMA Group

PURPOSE

To analyze the simultaneous combination of all-trans retinoic acid (ATRA) and anthracycline monochemotherapy for children with acute promyelocytic leukemia (APL).

PATIENTS AND METHODS

Since November 1996, 66 children (younger than 18 years) with genetically proven APL received induction therapy with ATRA and idarubicin. Consolidation therapy consisted of three courses of anthracycline monochemotherapy. After November 1999, patients with intermediate and high risk of relapse received consolidation therapy with ATRA and slightly reinforced doses of idarubicin. Maintenance therapy consisted of ATRA and low-dose mercaptopurine and methotrexate.

RESULTS

Thirty-nine girls (59%) and 27 boys (41%) were included in this study. The WBC count at presentation was more than 10 x 10(9)/L in 26 patients (39%). Sixty-one children (92%) achieved complete remission (CR). Early deaths from hemorrhage and retinoic acid syndrome occurred in three patients and two patients, respectively. Toxicity was manageable during consolidation and maintenance therapy. No deaths in CR, clinical cardiomyotoxicity, or secondary malignancy occurred. Two patients had molecular persistence at the end of consolidation. Three clinical relapses and two molecular relapses were also observed. Apart from one molecular relapse, all these events occurred among children with hyperleukocytosis. The 5-year cumulative incidence of relapse was 17%, whereas disease-free and overall survival rates were 82% and 87%, respectively.

CONCLUSION

A high incidence of hyperleukocytosis in children with APL was confirmed. Besides low toxicity and a high degree of compliance, a risk-adapted therapy combining ATRA and anthracycline monochemotherapy showed an antileukemic efficacy comparable to those previously reported with other chemotherapy combinations in children.

Long-term remission of APL with a second allogeneic BMT after CNS relapse following HLA-identical allogeneic BMT

Second allogeneic bone marrow transplantation (BMT) for AML relapsing after an initial BMT has a poor prognosis, with a probability of a 2-y disease-free survival below 30 per cent, caused both by treatment-related mortality (TRM) and high relapse rate. While TRM is most likely due to heavy pretreatment, AML relapse after BMT may be due to resistant disease or to a poor graft-versus-leukaemia (GvL) effect of the transplant. The degree of GvL may depend on individual donor/recipient immunoreactivity. In most published cases of second allogeneic BMT, both transplants were performed from the same donor. Here, we describe a patient who was first transplanted for acute promyelocytic leukaemia (APL) (AML FAB M3v) from his HLA-identical brother and received intensive immunotherapy including donor lymphocytes and IL2. He remained free from GvHD >I degrees, but developed CNS relapse. After a second BMT from another HLA-identical brother, he spontaneously developed GvHD III degrees, and has now been disease free for nearly 3 years. In this patient, long-term remission of AML relapsing after BMT was achieved by combining remission induction using an individual chemotherapy protocol with a second BMT from an alternative matched related donor and transient GvHD III degrees, which probably conferred a GVL effect.

Microgranular and t(11;17)/PLZF-RARalpha variants of acute promyelocytic leukemia also present the flow cytometric pattern of CD13, CD34, and CD15 expression characteristic of PML-RARalpha gene rearrangement

Acute promyelocytic leukemia (APL) is a subtype acute myeloid leukemia in which leukemic promyelocytes predominate in the bone marrow (BM). Rapid diagnosis is critical for treatment decision since all-trans-retinoic acid must be administrated promptly. The microgranular variant may be of difficult diagnosis, as it may be confused with other diseases on morphological grounds. The purpose of this study was to determine if the microgranular variant has the same antigenic profile as the classical hypergranular type. The immunophenotype of leukemic cells from the bone marrow of 50 patients, with the PML-RARalpha gene rearrangement confirmed by RT-PCR, was determined by flow cytometry using a large panel of 22 monoclonal antibodies and a polyclonal anti-TdT antibody. Thirty-four cases were classified as classical APL and 16 as microgranular APL. The immunophenotypic profile of the two subtypes was indistinguishable concerning the presence or absence of these antigens, including the absence of reactivity for the HLA-DR antigen. The simultaneous immunophenotypic combination of a unique major cell population, heterogeneous intensity of expression of CD13, and the typical pattern of CD15/CD34 expression were similarly present in the hypergranular and microgranular subtypes. Homogeneous expression of CD33 was observed in 76% of the classical APL cases and in 100% of the microgranular cases. Additionally, we have studied two cases of PLZF-RARalpha APL that also displayed the same immunophenotype described for classical APL. Thus, the immunophenotypic profile highly characteristic of the PML-RARalpha gene rearrangement was also observed in microgranular and PLZF-RARalpha variants of APL.

Outcome of Childhood Acute Promyelocytic Leukemia With All-Trans-Retinoic Acid and Chemotherapy

Purpose

To determine the results of treatment combining all-trans-retinoic acid (ATRA) and chemotherapy (CT) in childhood acute promyelocytic leukemia (APL).

Patients and Methods

Children (< 18 years) with newly diagnosed APL were included in the APL93 trial, treated by ATRA followed or combined with daunorubicin-cytarabine, and then randomly assigned between no maintenance, intermittent ATRA, continuous CT, or both.

Results

Of the 576 patients included in APL93 trial, 31 (5%) were children, including 22 girls (71%) and nine boys (29%). Thirty of the children (97%) obtained complete remission (CR). ATRA syndrome occurred in four children (13%), who all achieved CR, and headaches occurred in 12 children (39%), with signs of pseudotumor cerebri in five children (16%). Seven patients (23%) relapsed. None of the eight patients who received both ATRA and CT for maintenance relapsed. All relapsing patients achieved a second CR. Twenty-two patients remained in first CR after 43+ to 96+ months, six remained in second CR after 17+ to 66+ months, and three patients had died. The 5-year event-free survival (EFS), relapse, and overall survival rates were 71%, 27%, and 90%, respectively. No difference between adults and children included in the APL93 trial was seen for CR rate, 5-year relapse rate, EFS, and overall survival, but significantly better survival was seen in children after adjustment on WBC counts (P = .02) and incidence of microgranular M3 variant (P = .04).

Conclusion

ATRA combined with CT for induction and also probably for maintenance provides as favorable results in children with APL as in adults and currently constitutes the reference first-line treatment in both age groups.

Acute promyelocytic leukaemia in children

Acute promyelocytic leukaemia (APL), designated M3, is a particularly interesting subtype of acute myeloid leukaemia (AML) that has unique molecular and clinical characteristics. It is characterized by an arrest of myeloid differentiation at the promyelocyte stage with abnormal proliferation of these cells. Recent paediatric and adult trials which included all-trans retinoic acid (ATRA) have shown that APL has significantly better survival rates than other subtypes of AML. While there is extensive literature on APL in adults, articles dedicated to describing solely paediatric patients are limited. This chapter focuses on the incidence, diagnosis, clinical characteristics, treatment, and survival rates of children with APL.

Pathogenesis and management of the bleeding diathesis in acute promyelocytic leukaemia

Life-threatening bleeding, which remains a challenging complication of acute leukaemia, is particularly characteristic of the subtype, acute promyelocytic leukaemia (APL). The clinical picture and laboratory abnormalities are most compatible with the diagnosis of disseminated intravascular coagulation (DIC). Evidence for diffuse activation of the coagulation system, hyperfibrinolysis and systemic elaboration of non-specific protease activity can usually be demonstrated and occurs most commonly during induction chemotherapy. While both host- and tumour-associated mechanisms can be implicated in the pathogenesis of the coagulopathy, leukaemic cell properties appear to be the proximate cause of activation of the haemostatic mechanisms. In this chapter we summarize the current state of knowledge of the pathogenesis of the coagulopathy of APL and the therapeutic approaches that have proved most useful for the management of this complication. Special attention is devoted to the use of all-trans-retinoic acid (ATRA), which has revolutionized the treatment of APL and markedly ameliorated the APL-related coagulopathy.

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.

HLA-DR antigen-negative acute myeloid leukemia

Human leukocyte antigen (HLA) Class II antigens are variably expressed on acute myeloid leukemia (AML) blasts. The biological and clinical significance of HLA Class II antigen expression by AML cells is not known. Therefore, we sought to characterize cases of AML without detectable HLA-DR expression. Samples from 248 consecutive adult AML patients were immunophenotyped by multiparameter flow cytometry at diagnosis. HLA-DR antigens were not detected on AML cells from 43 patients, including 20 with acute promyelocytic leukemia (APL), and 23 with other subtypes of AML. All APL cases had t(15;17), but there were no characteristic chromosome abnormalities in non-APL cases. No direct expression of other antigens was identified in HLA-DR-negative APL and non-APL cases. Interestingly, cells from three HLA-DR-negative non-APL patients had similar morphology to that of the hypogranular variant of APL. This morphology, however, was not present in any HLA-DR-positive AML cases. Treatment response was similar in the 23 HLA-DR-negative non-APL and the 205 HLA-DR-positive patients. Finally, relapse was infrequently associated with changes in HLA-DR antigen expression, as the HLA-DR antigen was lost at relapse in only 4% of HLA-DR-positive cases, and was gained at relapse in only 17% of HLA-DR-negative cases. We conclude that HLA-DR-negative AML includes approximately equal numbers of APL and non-APL cases, and that the morphology of HLA-DR-negative non-APL cases can mimic the hypogranular variant of APL. The diagnosis of APL cannot be based on morphology and lack of HLA-DR antigen expression; rather, it requires cytogenetic or molecular confirmation.

New advances in the treatment of acute promyelocytic leukemia

OBJECTIVE

Describe the treatment options of newly diagnosed and relapsed APL.

INDUCTION

The fusion PML/RAR gene provided the rationale for using all-trans retinoic acid (ATRA) as differentiation therapy. The standard approach is antracycline + ATRA and no ARA-C.

CONSOLIDATION

Anthracycline based chemotherapy, no high dose ARA-C and perhaps no ARA-C. Maintenance seems to be important. Cure with ATRA + chemotherapy increased to 75% from 35% with chemotherapy alone.

POOR PROGNOSIS FACTORS

WBC >10,000, age >55, platelets <40,000 and CD 56 expression. Achieving and maintaining a molecular remission (MCR) i.e. RT-PCR (-) for PML/RAR alpha expression, is the best predictor for cure. Conversion to PCR (+) will eventually result in relapse. PCR monitoring in the first 2 years and intervention during molecular relapse would be safer than treatment in clinical relapse. Molecular relapses have been treated successfully by ATRA plus BMT. Arsenic trioxide (ATO) or gentuzumab (mylotarg) are also being studied.

RELAPSE (INDUCTION)

Patients after ATRA in first CR are less likely to respond to ATRA reinduction regardless of the time off ATRA and rarely achieve a molecular remission. Single-agent ATO induced in 52 relapsed patients CR of 87% (75% MCR) with low toxicity and no treatment related deaths (U.S. pivotal trial), confirmed in a NCI trial. Induction of relapsing patients with single agent ATO is preferable than ATRA + chemotherapy because the high molecular remission and lower toxicity.

RELAPSE (POST REMISSION)

No standard approach and the role of chemotherapy is unknown. ATO alone: in the pivotal trial, 9/21 patients had long remissions without other therapy. BMT: Not indicated in 1st MCR. In young patients auto BMT with PCR (-) harvests could be done in subsequent CR. Allo BMT has a higher death rate without overall better results. In the pivotal trial 12 patients were transplanted in CR after ATO alone (9 allo BMT) and 11 still without disease. Possibly allo BMT is safer after a less toxic ATO induction.

OTHER

ATO plus ATRA +/- AntiCD33 conjugated with toxin (gentuzumab) or 131I; Synthetic retinoid (Am80); histone deacetylase inhibitors; oral tetra-arsenic tetra-sulfide and various combinations.

Antigen expression patterns reflecting genotype of acute leukemias

Multi-parameter flow cytometry, molecular genetics, and cytogenetic studies have all contributed to new classification of leukemia. In this review we discuss immunophenotypic characteristics of major genotypic leukemia categories. We describe immunophenotype of: B-lineage ALL with MLL rearrangements, TEL/AML1, BCR/ABL, E2A/PBX1 translocations, hyperdiploidy, and myc fusion genes; T-ALL with SCL gene aberrations and t(5;14) translocation; and AML with AML1/ETO, PML/RARalpha, OTT/MAL and CBFbeta/MYH11 translocations, trisomies 8 or 11 and aberrations of chromosomes 7 and 5. Whereas some genotypes associate with certain immunophenotypic features, others can present with variable immunophenotype. Single molecules (as NG2, CBFbeta/SMMHC and PML/RARalpha proteins) associated with or derived from specific translocations have been described. More often, complex immunophenotype patterns have been related to the genotype categories. Most known associations between immunophenotype and genotype have been defined empirically. Therefore, these associations should be validated in independent patient cohorts before they can be widely used for prescreening of leukemia. Progress in our knowledge on leukemia will show how the molecular-genetic changes modulate the immunophenotype as well as how the expressed protein molecules further modulate cell behavior.

Acute promyelocytic leukemia: evolving therapeutic strategies

Acute promyelocytic leukemia (APL) is now the most curable subtype of acute myeloid leukemia in adults. All-trans retinoic acid (ATRA), which induces differentiation of the leukemic cells into mature granulocytes, represents the important advance. The incorporation of ATRA in induction results in a high complete remission rate, leads to rapid resolution of the characteristic life-threatening coagulopathy, and, most importantly, decreases the relapse rate compared with treatment with chemotherapy alone. However, ATRA is associated with unique toxicities not observed with conventional cytotoxic chemotherapy. A number of clinical trials have been performed to define the optimal role of ATRA in the treatment of patients. The therapeutic strategies have rapidly evolved as a result of both single institution and large cooperative group trials. Arsenic trioxide and stem cell transplantation are effective treatments for patients with APL who relapse after or are refractory to ATRA-based therapy. As experience with ATRA and arsenic trioxide in patients with APL accumulates, a number of important questions arise that need to be addressed.

A variant form of acute promyelocytic leukemia with marked myelofibrosis

We describe a variant form, French-American-British (FAB) M3v, of acute promyelocytic leukemia (APL; FAB M3) with atypical morphocytochemical features, immature antigens (CD34 and HLA-DR) and marked myelofibrosis (MF). Usual APL cells do not express CD34 or HLA-DR antigens. MF may be more frequently observed in patients with M3v expressing CD34 and HLA-DR antigens than in patients with M3 lacking these antigens. Despite marked MF, recovery from the hypoplastic phase in the case we described was not delayed after remission induction chemotherapy consisting of enocitabine, 200 mg/mi2 intravenously; 6-mercaptopurine, 70 mg/m2 orally for 10 days; daunorubicin 40 mg/m2 intravenously for 4 days; and all-trans retinoic acid 45 mg/M2 orally between days 20 and 33. The promyelocytic leukemia-retinoic-acid receptor (PML-RAR) alpha fusion transcript, according to reverse transcriptase-polymerase chain reaction (RT-PCR), became negative in the bone marrow after the first course of consolidation chemotherapy. Autologous peripheral blood stem cell transplantation (autoPBSCT) was carried out after 3 courses of consolidation chemotherapy. There were no specific complications based on MF throughout the clinical course, including engraftment in autoPBSCT. The patient has been without MF and in molecular remission, defined as disappearance of the PML-RAR alpha fusion transcript according to RT-PCR, for 21 months. Longer follow-up will clarify the effects of autoPBSCT on prognosis in APL with MF.

CD34-positive acute promyelocytic leukemia is associated with leukocytosis, microgranular/hypogranular morphology, expression of CD2 and bcr3 isoform

Acute promyelocytic leukemia (APL) has a favorable prognosis. Current therapy includes chemotherapy used in combination with all-trans-retinoic acid (ATRA). Although the differentiating effects of ATRA on promyelocytes have been well established, in vitro studies have shown that less-differentiated APL blasts (CD34(+)) demonstrate a variable responsiveness to ATRA. To assess the clinical relevance of this finding, we analyzed a cohort of 38 patients with t(15;17) and/or PML-RARalpha APL to determine the incidence and laboratory features of CD34(+) APL. Thirty-two percent (12/38) of cases were CD34(+). There was a difference in WBC at presentation between CD34(+) and CD34(-) cases (34.6 +/- 9.2, mean +/- standard error vs. 5.4 +/- 2.0, P = 0.009). Patients with CD34(+) APL demonstrated a micro/hypogranular phenotype (75%) (P = 0.001), co-expression of CD2(+) (83%) (P = 0.001), and the bcr3 isoform (100%) (P = 0.017). In contrast, CD34(-) cases demonstrated hypergranular morphology (65%), CD2(+) (15%), and the bcr1 isoform (50%). A high presenting WBC count (\G10 x 10(9)/L) was associated with an inferior overall survival (Log rank = 0.0047). Patients with CD34(+) APL demonstrated an incidence of early mortality of 50%. Despite a marked correlation between CD34 positivity and increased WBC count, overall survival of CD34(+) and CD34(-) cases did not differ significantly in our small cohort. Immunophenotypic analysis for CD34 expression should be included in future large APL trials to determine if detection of CD34(+) blasts represents an independent adverse prognostic factor.

Transcription therapy for acute promyelocytic leukaemia

Transcription factors are proteins that regulate gene transcription and expression. In many cases of acute leukaemia chromosomal aberrations are translocations of transcription factors which change their expression and induce the leukaemic phenotype. These abnormal transcription factors are tumour-specific and can be targets for novel treatments approaches. Acute promyelocytic leukaemia (APL) is a distinct and unique subtype of acute myeloid leukaemia (AML) characterised by a reciprocal translocation between chromosomes 15 and 17 t(15q22;17q21). The breakpoints of chromosome 15 and 17 are in the PML and RARalpha genes, respectively, forming the fusion PML-RARalpha gene expressed exclusively and universally in APL. The normal RARalpha is an all-trans retinoic acid- (ATRA-)dependent transcription factor involved in the normal differentiation of myeloid cells. The aberrant fusion PML-RARalpha protein remains sensitive to ATRA and underlies the pathogenesis of the APL. ATRA modulation of gene transcription mediated by PML-RARalpha results in a major clinical response. Almost all newly diagnosed APL cases can be induced into complete remission with ATRA with or without chemotherapy by in vivo differentiation of the APL cells. Randomised clinical trials have shown that the most significant effect of ATRA is an additive or synergistic activity with chemotherapy to improve the long-term outcome of the disease. On the other hand, ATRA with or without induction chemotherapy did not increase the complete remission rate compared to chemotherapy alone. In addition, the relapse rate was significantly lower for patients randomised to induction with concurrent ATRA/chemotherapy than with ATRA followed by chemotherapy. Chemotherapy and/or ATRA maintenance may further improve the long-term outcome compared to no maintenance. PML-RARalpha fusion transcripts can be assayed by RT-PCR to identify PCR positive cells during remission, which are highly predictable of a subsequent haematological relapse. The goal of therapy has been modified to induce a molecular remission with a negative PCR to the PML-RARalpha transcript. This is the first example of an effective response to treatment with a ligand binding to a mutated form of its natural transcription factor. The transcription factor mutation, caused by translocation to another gene, underlies the pathogenesis of the disease.

Immunophenotype of adult and childhood acute promyelocytic leukaemia: correlation with morphology, type of PML gene breakpoint and clinical outcome. A cooperative Italian study on 196 cases

Acute promyelocytic leukaemia (APL), characterized by a specific PML-RARalpha fusion gene resulting from translocation t(15;17) and by a high response rate to differentiation therapy with all-trans retinoic acid, presents clinical (varying WBC counts, age and treatment outcome), morphological (hypergranular M3 and hypogranular M3V) and molecular (three isoforms of PML breakpoint) heterogeneity. We correlated leukaemic immunophenotype with these aspects in 196 molecularly confirmed APLs (63 children and 133 adults) in Italy. The bcr3 isoform (P = 0.05) and FAB M3V (P = 0.05) were more frequent in children. We confirmed in APL an immunophenotype characterized by frequent expression of CD13, CD33 and CD9 and rare expression of HLA-DR, CD10, CD7 and CD11b. However, we recognized CD2 in 28%, CD34 in 23% and CD19 in 11% of cases and demonstrated by double labelling that CD34 and CD2 may be co-expressed. CD2, CD34 and CD19 were significantly intercorrelated, and variably associated to other features: CD2 and CD34 with PML bcr3 (P < 0.001 and P < 0.001, respectively) and with M3V (P < 0.001 and P = 0.002), whereas only CD19 was directly correlated with WBC counts and only CD2 positively influenced CR rate (logistic model) and event-free survival (Cox model). We conclude that immunophenotype plays a role in the determination of the biological and clinical heterogeneity of childhood and adult APL.

Morphology of acute promyelocytic leukemia with cytogenetic or molecular evidence for the diagnosis: characterization of additional microgranular variants

Early diagnosis of t(15;17) acute promyelocytic leukemia (APL) is essential because of the associated disseminated intravascular coagulation and the unique response of the disease to all-trans retinoic acid (ATRA) therapy. Early diagnosis depends primarily on morphological recognition. The French-American-British (FAB) classification, however, does not describe all morphological variations that occur in APL. In 25 cases with evidence of APL confirmed by cytogenetic and/or molecular analysis, we found a heterogeneous morphological group. The most common form of APL was heterogeneous and consisted of various combinations of cells in which hypergranular cells and some cells with multiple Auer rods were obvious. In some cases, one cell predominated. This led to the description of five subcategories. These included the classical FAB M3 with hypergranular cells and multiple Auer rods; the FAB variant with hypogranular bilobed cells; the basophilic cell type of McKenna et al. [Br. J. Haematol 50:201, 1982]; and two additional subtypes, one consisting of differentiated promyelocytes and a few blast cells (M2-like), and the other consisting largely of blast cells and a few early promyelocytes (M1-like). Immunophenotyping revealed a pattern of CD33 and/or CD13 positivity, and CD14 and HLA-DR negativity in 96% of cases. CD2 was positive in the FAB variant and in the subtype with basophilic cells, but negative with other subtypes. Three out of five cases with basophilic cell predominance [McKenna et al.: Br J Haematol 50:201, 1982], and one out of two M2-like cases, responded to ATRA therapy. Awareness of the heterogeneity and the atypical morphologic subtypes found in t(15;17) APL will contribute to improved recognition and early institution of ATRA therapy.

A microgranular variant of acute promyelocytic leukemia with atypical morpho-cytochemical features and an early myeloid immunophenotype

This report describes a unique case of acute promyelocytic leukemia (APL) showing elusive morphologic features, an atypical pattern of cytochemical reactions, and a previously unreported immunophenotype consistent with a very early myeloid form: CD13 (+), CD33 (+), CD9 (+), CD2 (+), HLA-DR (-), CD34 (+), CD117 (+), and TdT (+). The diagnosis of AML M3 variant was made only after genotypic analyses revealed the PML/RAR alpha rearrangement associated with the typical (15;17) (q22;q21) translocation. This example of 'asynchronous differentiation' emphasizes the need for a multiparameter approach to the diagnosis of acute leukemia.

Adult acute leukemia

Untreated acute leukemia is a uniformly fatal disease with a median survival time shorter than 3 months. Current treatment strategies provide a significant increase in survival time for most patients, some of whom may be cured. The majority of patients with acute leukemia, however, ultimately die of the disease or complications of treatment. The effective treatment of acute leukemia requires (1) differentiation of acute myeloid leukemia (AML) from acute lymphoblastic leukemia (ALL) and recognition of clinically relevant subtypes; (2) identification of patients who are more likely or less likely than average to benefit from a conventional treatment; and (3) selection of therapy that provides a reasonable likelihood of response with acceptable risk of toxic effects. The diagnosis of acute leukemia is established in most cases by a bone marrow aspirate that demonstrates at least 30% blast cells. The traditional criteria to distinguish between AML and ALL rely on morphology and cytochemical reactions. Immunologic analysis of antigen expression and analysis for numerical or structural chromosomal abnormalities of leukemia cells are routinely feasible. Karyotypic analysis is of prognostic importance and should be performed on all diagnostic specimens of bone marrow aspirate. Immunophenotypic analysis may be useful to confirm the disease classification in selected cases. The importance of the routine immunophenotypic characterization of acute leukemia, however, is controversial. The subtypes that must be recognized because of the need for specific treatment include (a) acute promyelocytic leukemia (APL), which is the M3 subtype of AML, and (b) the L3 subtype or mature B-cell ALL. Induction therapy for acute leukemia is treatment intended to achieve induction of complete remission (CR). Complete remission is defined as the absence of morphologic evidence of leukemia after recovery of the peripheral blood cell counts. Failure to achieve CR may be attributed to death during chemotherapy-induced bone marrow hypoplasia or to drug resistance manifested either as failure to achieve hypoplasia or as persistent leukemia after recovery from hypoplasia. Postremission therapy is treatment administered in CR to prevent or delay relapse of the leukemia. However, the majority of patients have disease relapse. Intensification of therapy is a treatment strategy designed to overcome resistance to chemotherapy. Recent clinical trials of intensified induction or postremission therapy suggest improved outcome. However, the toxic effects of dose intensification can be substantial, limiting any potential benefit of this approach. Identification of prognostic factors may allow one to estimate the likelihood of an outcome, to determine an optimal treatment strategy. It is well established that age at the time of diagnosis, leukemia cell karyotype, and whether the leukemia is de novo or secondary are factors that influence treatment decisions. Patients with favorable prognostic factors should probably receive conventional therapy. Patients with unfavorable prognostic factors have shown little benefit from conventional therapy. In addition, factors that indicate poor outcome with conventional therapy are also predictive of poor outcome with intensified therapy. Consequently, these patients should be considered for investigational therapeutic strategies. The bias may be to counsel them to accept the potential increased morbidity of such treatment before there is definite evidence of the possibility of improved outcome. Induction chemotherapy for younger patients with AML (less than 55 years of age) in general consists of one or more courses of cytarabine (ara-C) and an anthracycline or an anthracycline derivative. Randomized trials have failed to confirm that treatment with either etoposide or high-dose ara-C induces disease remission. Patients with secondary AML, high levels of CD34 antigen expression, or an unfavorable karyotype, however, may benefit from ind

Use of all-trans retinoic acid to treat acute promyelocytic leukemia: a case with very severe features at the onset in Nicaragua

We observed a child with acute promyelocytic leukemia (APL) who, at the onset, had extremely severe hemorrhagic and septic complications. According to our experience in Nicaragua, there was a very high risk of early death. The patient was successfully treated with a program that included all-trans retinoic acid (ATRA) followed by cytotoxic chemotherapy. ATRA has two important features: it is effective in initial treatment of APL and it is inexpensive. Because of the high cost and the need for extensive supportive care, optimal myeloablative therapy used in patients with various types of acute myeloid leukemia generally cannot be given in developing countries. ATRA treatment for APL is affordable everywhere.

Reverse transcription polymerase chain reaction for the diagnosis and molecular monitoring of the PML/RAR alpha fusion gene in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is characterized by a specific t(15;17) translocation and a high rate of response to all-trans retinoic acid. The translocation generates a PML/RAR alpha chimeric gene which is transcribed in a fusion PML/RAR alpha mRNA. In this study, by using RT-PCR, we examined 14 APL patients for PML/RAR alpha fusion gene transcripts. Eight patients were studied at diagnosis, 2 at relapse, 1 both at relapse and after reinduction, 1 both at diagnosis and after three cycles of consolidation chemotherapy, and 2 patients were examined for minimal residual disease (MRD) 4 months after completing treatment. A positive result was observed in all 14 cases. Two patients who were in complete hematologic remission had evidence of hematologic relapse soon after the positive test. We conclude that RT-PCR for APL yields important diagnostic and prognostic information for the APL patients.

Contribution of immunophenotypic and genotypic analyses to the diagnosis of acute leukemia

Diagnostic accuracy in acute leukemia (AL) can be improved if traditional morphology and cytochemistry are supplemented with immunophenotypic and genotypic analyses. This multiparameter approach is of crucial importance for the management of patients, as it enables the identification of leukemic syndromes with distinct biological features and response to treatment. Immunophenotyping using monoclonal antibodies has been universally accepted as a useful adjunct to morphological criteria. This technique is particularly valuable in diagnosing and subclassifying acute lymphoblastic leukemia and is also essential in certain types of acute myeloid leukemia (AML), such as AML with minimal differentiation or acute megakaryoblastic leukemia. Cytogenetic findings can be quite helpful in establishing the correct diagnosis and can add information of prognostic significance. A number of specific chromosomal abnormalities have been recognized that are very closely, and sometimes uniquely, associated with morphologically and clinically distinct subsets of leukemia. An even more basic understanding of normal and malignant hematopoietic cells has begun to evolve as molecular biology begins to unravel gene misprogramming by Southern and Northern blot analysis, the polymerase chain reaction, and fluorescence in situ hybridization. With the extensive use of these techniques it has become apparent that a proportion of leukemias exhibit the biologically relevant molecular defect in the absence of a karyotypic equivalent. On the other hand, apparently uniform chromosomal abnormalities such as the t(1;19) (q23;p13), t(9;22) (q33;q11), t(8;14) (q24;q32), or t(15;17) (q21;q21) may differ at the molecular level. Data collected from these modern technologies have introduced a greater complexity, which needs to be taken into consideration to improve both the diagnostic precision and the reproducibility of current classifications.

Acute promyelocytic leukaemia with hypogranular bone marrow blasts in a 16-year-old girl: diagnostic value of different genetic methods

We report a 16-year-old girl who presented with anaemia, thrombocytopenia, leukocytosis and disseminated intravascular coagulation. Bone marrow analysis showed promyelocyte-like myeloblasts with rare Auer rods and very few granula. CD2 antigen was not expressed in bone marrow blasts. Karyotype analysis revealed a complex pattern of chromosomal aberrations without the promyelocytic leukaemia (PML) specific translocation t(15;17) (q22;q21). Southern blot analysis revealed a rearrangement of the retinoic acid receptor alpha (RAR alpha) locus. Reverse transcribed polymerase chain reaction assay confirmed the initial diagnosis of PML by amplification of the PML-specific PML/RAR alpha fusion transcript.

CONCLUSION

This case report confirms that a characteristic translocation t(15;17) is not always detectable in PML blasts by karyotype analysis despite presence of specific PML/RAR alpha-transcripts. Together with careful morphological analysis of bone marrow blasts this assay apparently is the most specific and sensitive method to confirm the diagnosis.

Clinical relevance of the PML/RAR-a gene rearrangement in acute promyelocytic leukaemia

The molecular mechanisms underlying the t(15;17) cytogenetic translocation of acute promyelocytic leukaemia (APL) have been recently elucidated. Together with new insights into the understanding of APL pathogenesis, such investigations also provided the availability of a novel leukemia-specific marker to be used for both diagnostic and monitoring studies. The chromosome breakpoints of the t(15;17) have been shown to involve the retinoic acid receptor alpha (RAR-a) gene and the newly described PML gene on chromosomes 17 and 15, respectively. Rearrangements of these loci are found in virtually 100% of APLs, including the microgranular variant subtype and cases displaying apparently normal karyotypes. In cases with ambiguous morphology, molecular diagnosis may therefore enable the prompt administration of APL-specific therapies, such as all-trans retinoic acid. Significantly, clinical response to this differentiating agent is predictable based on the presence of the specific PML/RAR-a rearrangement. Appropriate oligoprimers complementary to PML and RAR-a sequences nearby the DNA breakpoints may be successfully used in PCR experiments to amplify the PML/RAR-a hybrid gene and sensitively detect minimal residual disease. Preliminary PCR studies indicate that this approach might indeed prove a very important and reliable prognostic indicator in the follow up monitoring of APL patients. Early identification of impending relapse by PCR may suggest the use of additional treatment in patients at risk and significantly increase the probability of cure of the disease.

Childhood acute promyelocytic leukemia in Nicaragua

BACKGROUND

The pediatric hematology-oncology service of the Managua 'La Mascota' Children's Hospital in Nicaragua began its activities in 1988. We report on unusual high incidence of acute promyelocytic leukemia (APL) observed in Nicaragua in the last three years.

PATIENTS AND METHODS

From 1990 to 1992, 17 of 110 children with acute leukemia were diagnosed as having acute non-lymphoblastic leukemia (AnLL). The diagnosis was performed according to the FAB criteria. In two cases DNA was recovered for molecular analysis of the t(15; 17).

RESULTS

Ten of 17 cases of AnLL were classified as APL. PML and RAR alpha gene rearrangements were observed in the two cases where molecular analysis was performed. Nine children received chemotherapy; one was treated with all-trans-retinoic acid (ATRA), achieving complete remission. Eight children who received chemotherapy died early of hemorrhage and/or sepsis.

DISCUSSION

In Nicaragua, APL may be much more common than is generally observed elsewhere. In recent years initial treatment of APL with ATRA has proved to reduce the incidence of early hemorrhagic deaths, and complete remissions can be achieved without marrow aplasia and thus prevent infectious complications. From that perspective APL might become a curable disease, also in developing countries where the treatment of AnLL is not usually affordable.