Acute promyelocytic leukemia--clinical management of 15 patients

History of Acute Promyelocytic Leukemia

In this article, we discuss the history of acute promyelocytic leukemia (APL) from the pre-therapeutic era, which began after its recognition by Hillestad in 1947 as a nosological entity, to the present day. It is a paradigmatic history that has transformed the “most malignant leukemia form” into the most curable one. The identification of a balanced reciprocal translocation between chromosomes 15 and 17, resulting in fusion between the promyelocytic leukemia gene and the retinoic acid receptor alpha, has been crucial in understanding the mechanisms of leukemogenesis, and responsible for the peculiar response to targeted therapy with all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). We review the milestones that marked successive therapeutic advances, beginning with the introduction of the first successful chemotherapy in the early 1970s, followed by a subsequent incorporation of ATRA and ATO in the late 1980s and early 1990s which have revolutionized the treatment of this disease. Over the past two decades, treatment optimization has relied on the combination of ATRA, ATO, and chemotherapy according to risk-adapted approaches, which together with improvements in supportive therapy have paved the way for cure for most patients with APL.

Acute Promyelocytic Leukemia: A History over 60 Years-From the Most Malignant to the most Curable Form of Acute Leukemia

Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia (AML) that is cytogenetically characterized by a balanced reciprocal translocation between chromosomes 15 and 17, which results in the fusion of the promyelocytic leukemia (PML) and retinoic acid receptor alpha (RARα) genes. Because patients with APL present a tendency for severe bleeding, often resulting in an early fatal course, APL was historically considered to be one of the most fatal forms of acute leukemia. However, therapeutic advances, including anthracycline- and cytarabine-based chemotherapy, have significantly improved the outcomes of APL patients. Due to the further introduction of all-trans retinoic acid (ATRA) and-more recently-the development of arsenic trioxide (ATO)-containing regimens, APL is currently the most curable form of AML in adults. Treatment with these new agents has introduced the concept of cure through targeted therapy. With the advent of revolutionary ATRA-ATO combination therapies, chemotherapy can now be safely omitted from the treatment of low-risk APL patients. In this article, we review the six-decade history of APL, from its initial characterization to the era of chemotherapy-free ATRA-ATO, a model of cancer-targeted therapy.

Mutant Isocitrate Dehydrogenase Inhibitors as Targeted Cancer Therapeutics

The identification of heterozygous neomorphic isocitrate dehydrogenase (IDH) mutations across multiple cancer types including both solid and hematologic malignancies has revolutionized our understanding of oncogenesis in these malignancies and the potential for targeted therapeutics using small molecule inhibitors. The neomorphic mutation in IDH generates an oncometabolite product, 2-hydroxyglutarate (2HG), which has been linked to the disruption of metabolic and epigenetic mechanisms responsible for cellular differentiation and is likely an early and critical contributor to oncogenesis. In the past 2 years, two mutant IDH (mutIDH) inhibitors, Enasidenib (AG-221), and Ivosidenib (AG-120), have been FDA-approved for IDH-mutant relapsed or refractory acute myeloid leukemia (AML) based on phase 1 safety and efficacy data and continue to be studied in trials in hematologic malignancies, as well as in glioma, cholangiocarcinoma, and chondrosarcoma. In this review, we will summarize the molecular pathways and oncogenic consequences associated with mutIDH with a particular emphasis on glioma and AML, and systematically review the development and preclinical testing of mutIDH inhibitors. Existing clinical data in both hematologic and solid tumors will likewise be reviewed followed by a discussion on the potential limitations of mutIDH inhibitor monotherapy and potential routes for treatment optimization using combination therapy.

Acute promyelocytic leukemia: where did we start, where are we now, and the future

Historically, acute promyelocytic leukemia (APL) was considered to be one of the most fatal forms of acute leukemia with poor outcomes before the introduction of the vitamin A derivative all-trans retinoic acid (ATRA). With considerable advances in therapy, including the introduction of ATRA initially as a single agent and then in combination with anthracyclines, and more recently by development of arsenic trioxide (ATO)-containing regimens, APL is now characterized by complete remission rates of 90% and cure rates of ∼80%, even higher among low-risk patients. Furthermore, with ATRA-ATO combinations, chemotherapy may safely be omitted in low-risk patients. The disease is now considered to be the most curable subtype of acute myeloid leukemia (AML) in adults. Nevertheless, APL remains associated with a significant incidence of early death related to the characteristic bleeding diathesis. Early death, rather than resistant disease so common in all other subtypes of AML, has emerged as the major cause of treatment failure.

Inching toward cure of acute myeloid leukemia: a summary of the progress made in the last 50 years

Despite some claims to the contrary, I believe substantial progress has been made in the last half century toward cure of acute myeloid leukemia in children and adults. The tried and true mechanism for this progress has been clinical trial and error. This method has been supplemented with an ever-increasing amount of work at the clinical laboratory interface that is beginning to allow us to develop specific therapy for afflicted individuals. This review details where we stand today and how we got here.

Treating childhood acute myeloid leukaemia with the AML-BFM-83 protocol: experience in a developing country

Treatment for childhood acute myeloid leukaemia (AML) consists of remission induction chemotherapy followed by postremission chemotherapy with or without bone marrow transplantation. The AML Berlin-Frankfurt-Munster (BFM)-83 protocol with induction-consolidation-maintenance chemotherapy for 2 years has been reported to result in a 6-year event-free survival (EFS) and event-free interval (EFI) of 49% and 61% respectively. A total of 174 Malaysian children were treated with this protocol between 1985 and 1999. The 5-year EFS and EFI was 30.7% and 48.0% respectively. The overall mortality from sepsis was 24%, which needs urgent address. The 5-year EFS for patients treated before 1993 and after 1993 was 18.6% and 41.3%, respectively (P = 0.04), while the EFI was 32% and 60.6% respectively (P = 0.034). The improvement seen after 1993 was related to a reduction in induction deaths for that period and probably reflected increased capability and familiarity to cope with the demands of the AML-BFM-83 protocol and accompanying complications in the treatment of AML.

Choice of chemotherapy in induction, consolidation and maintenance in acute promyelocytic leukaemia

Cure of acute promyelocytic leukaemia (APL) is now a reality for most patients through the use of combined all-trans retinoic acid (ATRA) and chemotherapy. The simultaneous administration of ATRA and anthracycline-based chemotherapy is currently considered the most appropriate induction therapy. However, no consensus has been reached on the consolidation strategy. Therapeutic efficacy apparently did not differ according to the number of cycles and types of drug combined with anthracyclines. Encouraging results have been reported recently using less-intensive chemotherapy with anthracyclines alone, leading to a significant reduction in treatment-related toxicity during the consolidation phase and a high degree of compliance. Some ongoing risk-adapted protocols are now exploring the potential synergistic effect of ATRA and chemotherapy given simultaneously in consolidation. Preliminary data suggest that higher molecular remission rates post-consolidation and improved outcome may be obtained through this strategy. Persistence or recurrence of molecular disease at the end of consolidation is strongly associated with impending relapse and poor prognosis, indicating the need for further aggressive therapy. As for maintenance therapy, once demonstrated, the advantage of using ATRA with or without low-dose methotrexate and 6-mercaptopurine has encouraged most groups to incorporate such treatment into their protocols for APL.

Differentiating agents in pediatric malignancies: all-trans-retinoic acid and arsenic in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is the most potentially curable type of acute myeloid leukemia. It is characterized by the chromosomal translocation t(15;17), which results in the fusion gene PML-RAR-alpha. The introduction of all-trans- retinoic acid (ATRA) was a major advance in treatment of this disease. This agent induces terminal differentiation of malignant myeloid cells to mature neutrophils, and its side effects are usually well tolerated in children. ATRA does not eradicate the malignant myeloid clone in APL and, eventually, resistance develops. Arsenic trioxide induces nonterminal differentiation of malignant promyelocytes and promotes apoptosis. APL patients treated with ATRA or arsenic trioxide have rapid resolution of their coagulopathy. Because both of these drugs are well tolerated in children and their synergy has been shown in animal models, the possibility of combining ATRA and arsenic trioxide in front-line therapy for children with APL is being considered.

Acute promyelocytic leukaemia in the all trans retinoic acid era

Bleeding diathesis is a common complication of acute promyelocyctic leukaemia (APL). Multiple haemostatic defects are found in most patients with APL, which often worsen following cytoreductive chemotherapy. Besides thrombocytopenia, most patients develop disseminated intravascular coagulation, systemic fibrinolysis or both. A major aim in treating haemostatic defects of APL is to prevent death or disability from bleeding until chemotherapy clears the malignant promyelocytes from the blood and bone marrow. The therapeutic options are discussed in this review and practical guidelines for treatment are outlined.

Coagulation disorders in cancer

Coagulation disorders are common in cancer patients. This article reviews the coagulation laboratory findings in these patients and the thromboembolic and hemorrhagic manifestations of malignancy. Among the many topics addressed are Trousseau's syndrome, disseminated intravascular coagulation, and acquired von Willebrand disease. Pathogenesis of the coagulation disorders and recommendations for treatment of various syndromes are discussed.

Coincidence of acquired factor-X deficiency and disseminated intravascular coagulation in patients with acute nonlymphoblastic leukemia

Systematic clotting studies were performed in 157 patients with de novo acute nonlymphoblastic leukemia (ANLL) prior to treatment. Sixteen patients had disseminated intravascular coagulation (DIC). Three of the patients with DIC (two with M3, one with M5 leukemia) had a marked isolated factor-X deficiency (factor X:C 21%, 33%, and 41%, respectively). Another four patients had a mild isolated factor-X deficiency (factor X:C 55%-68%). In these seven patients the remaining liver-synthesized clotting factors (factors II, VII, IX, V) as well as serum albumin and cholinesterase were within the normal range. Liver disease or vitamin-K deficiency could therefore be excluded. In none of the 141 patients without DIC was a marked isolated factor X deficiency observed; two patients had moderately reduced factor X:C levels but normal liver-synthesized proteins. Induction treatment led to the control of DIC with an almost parallel increase of fibrinogen and factor X up to normal in all patients with factor-X deficiency who achieved complete remission. In one patient, recurrence of leukemia was associated with reoccurrence of DIC and marked factor-X deficiency. We conclude that there is a coincidence of isolated factor-X deficiency and DIC in some patients with ANLL. In some patients, this factor-X deficiency may be severe enough to contribute to the bleeding tendency.

Complete remission in acute promyelocytic leukemia despite the persistence of the 15;17 translocation

Acute promyelocytic leukemia (APL) is a morphologically distinct subtype of acute non-lymphocytic leukemia (ANLL) characterized cytogenetically by the presence of a translocation between chromosomes 15 and 17 (t(15;17]. In contrast to other subtypes of ANLL, morphologic examination of the bone marrow in the early postinduction period fails to identify patients adequately who have a high likelihood of entering remission. Remission has frequently been achieved in APL despite the failure to attain marrow aplasia or eliminate dysplastic progranulocytes after initial induction chemotherapy. In a patient with APL who failed to achieve cytoreduction after a single course of induction chemotherapy, serial cytogenetic studies demonstrated persistence of metaphases with the t(15;17) up to 23 days after induction. However, complete morphologic and cytogenetic remission was subsequently attained by day 29 without further therapy. In APL remission may occur even when induction therapy fails to achieve marrow aplasia or to eradicate replicative cells with abnormal karyotype promptly. In order to avoid excessive exposure to toxic therapy, new strategies may be necessary to identify, early in treatment, patients with APL who will require only one course of induction chemotherapy to enter remission successfully.

Microgranular promyelocytic leukemia: a multiparameter examination

Six cases of microgranular variant acute promyelocytic leukemia (M3v) were studied by use of a multiparameter approach including morphology, cytochemistry, flow cytochemistry, flow cytometry, cytogenetics, and gene rearrangement. Three of six cases demonstrated both myeloid and monocytoid associated surface markers by flow cytometry. One of six cases had strong alpha-naphthyl-butyrate esterase (alpha-NBE) activity in addition to myeloperoxidase activity. There was no correlation between percentage of positive monocytoid surface markers and intensity of cytoplasmic alpha-NBE activity. Four of six cases also had a T-cell-associated surface antigen. Further studies indicated that the T-cell markers appeared to be on the promyelocytes and that the T-B receptor gene was not rearranged. Similarly, cytogenetics studies indicated only one clonal abnormality t(15q+; 17q-). Whether these cases represent true "lineage infidelity" remains to be answered. Future important studies are needed on normal hematopoietic progenitor cells at early stages of development and childhood to study lineage-specific characteristics and to determine whether co-expression normally exists during early development.

Beneficial effect of heparin in the management of patients with APL

115 patients with acute promyelocytic leukaemia (APL) were studied retrospectively to evaluate prognostic factors and assess therapeutic approaches, particularly the use of heparin in the management of disseminated intravascular coagulation (DIC). The remission rate was 86% (30/35 patients) in those who received heparin and 49% (39/80 patients) in those who received no heparin (P = 0.0002). This difference in remission rates was accounted for by a marked decrease in the number of haemorrhagic deaths, especially those due to intracranial haemorrhage (ICH), in the heparin treated group. Other factors associated with a poor remission rate were prothrombin ratio (PTR) greater than 1.3 (P = 0.008), fibrinogen less than 1.5 g/l (P = 0.02) and WCC greater than 2.0 x 10(9)/l (P = 0.03).

Potential role of interleukin-1 as the trigger for diffuse intravascular coagulation in acute nonlymphoblastic leukemia

Abnormalities of coagulation are common in patients with acute nonlymphoblastic leukemia, although the mechanisms involved are unclear, except in a few cases. To investigate the pathogenesis of this coagulopathy, suspensions of purified leukemic cells were prepared and tested for procoagulant activity. Neither the leukemic cells nor their supernatants directly accelerated the clotting of plasma. Since the leukemic cells did not possess direct procoagulant activity, their ability or inability to elaborate a mediator of cellular coagulant properties, interleukin-1, was studied. Leukemic cells from patients with coagulopathy elaborated interleukin-1, and addition of phytohemagglutinin increased interleukin-1 release. In contrast, no interleukin-1 was released, before or after stimulation with phytohemagglutinin, from leukemic cells from patients without coagulopathy. Leukemic cells from another group of patients with abnormalities of coagulation released interleukin-1 only after phytohemagglutinin treatment. In terms of the coagulation mechanism, interleukin-1 containing supernatants from leukemic cell cultures induced the procoagulant receptor tissue factor, a co-factor in the initiation of coagulation, on the endothelial cell surface. There was coordinate suppression of the anticoagulant endothelial cell receptor thrombomodulin, a co-factor for the antithrombotic protein C pathway. Antibody to interleukin-1 prevented these changes in cellular coagulant properties. Taken together, these changes result in a shift in the balance of endothelial cell coagulant properties to an activated state in which mechanisms promoting procoagulant reactions on the vessel surface predominate. Synthesis and release of the mediator interleukin-1 by leukemic cells thus defines a new mechanism through which malignant cells can potentially activate the coagulation mechanism.

Early deaths due to hemorrhage and leukostasis in childhood acute myelogenous leukemia. Associations with hyperleukocytosis and acute monocytic leukemia

There were 294 children with acute myelogenous leukemia (AML) entered into the German AML Berlin, Frankfurt, and Münster hospitals (BFM) 78 and 83 studies. Thirty (10%) died as a result of hemorrhage and/or leukostasis prior to or in the first 12 days of therapy. The risk of early death due to hemorrhage and/or leukostasis is significantly greater when certain features are initially present: acute monocytic leukemia (French-American-British [FAB] M5), hyperleukocytosis (greater than or equal to 100,000/microliter), and extramedullary organ involvement (P less than 0.001). The risk increases sharply when these factors exist in combination: 72% mortality with FAB M5 and hyperleukocytosis, and 43% with FAB M5 and extramedullary organ involvement. In 11 patients leukostasis alone or in combination with hemorrhage was probably the cause of death during the first 3 days after diagnosis. All 11 children presented with hyperleukocytosis and were classified as monocytic subtype FAB M4 or M5. After induction, a close temporal association between rapid blast reduction and occurrence of fatal hemorrhage was established in five patients. Thrombocytopenic hemorrhages were controllable and, therefore, responsible for death only in exceptional cases. It is difficult to avoid these early fatal complications with current therapeutic measures. Early exchange transfusion together with special supportive care may be useful.

Role of maintenance chemotherapy in acute promyelocytic leukemia

The effect of maintenance chemotherapy on remission duration was analyzed in 39 of 70 patients (56%) with acute promyelocytic leukemia (APL) who achieved complete remission on induction chemotherapy. Overall, the median remission duration was 26 months, with a 3-year remission rate of 42%. The 3-year remission rate was significantly higher in patients who received 6-mercaptopurine and methotrexate (POMP) during maintenance, compared with those who did not (56% versus 30%; P less than 0.01), and in patients who received long-term maintenance therapy (P less than 0.01). A multivariate regression analysis selected maintenance therapy with POMP to be the only statistically significant factor associated with long-term remission duration. The type of maintenance chemotherapy is important in overall prognosis of patients with APL, and should be investigated further.

Variant translocation t(8;22) and abnormalities of chromosome 15(q22) and 17(q12-21) in a Burkitt's lymphoma/leukaemia with disseminated intravascular coagulation

Severe disseminated intravascular coagulation was observed in a patient with Burkitt's lymphoma/leukaemia. Immunological studies on leukaemic blasts from relapsed bone marrow revealed a B-cell phenotype (B4+, B1+, HLA-Dr+, J5+) with membrane bound IgM lambda. Cytogenetic investigation revealed a variant Burkitt's translocation t(8;22)(q24;q11) involving the lambda light chain gene region and abnormalities of chromosomes 15 and 17 with breakpoints at q22 and q12 respectively, similar to those observed in the t(15;17) in acute promyelocytic leukaemia. Transmission electron microscopy of the leukaemic blasts showed crystalline cytoplasmic inclusions which may have had a role in precipitating the disseminated intravascular coagulation.

Treatment of disseminated intravascular coagulation in acute promyelocytic leukemia with low molecular weight heparinoid Org 10172

Four patients with acute promyelocytic leukemia (APL) and clinical and laboratory manifestations of disseminated intravascular coagulation (DIC) were treated during induction chemotherapy with Org 10172 (Organon International), a low molecular weight heparinoid preparation. Plasma anti-Xa levels were maintained between 0.60 and 0.80 U/ml and anticoagulant activities, determined with a diluted activated partial thromboplastin time assay, ranged from 0.00 to 0.20 U/ml. Bleeding symptoms ceased and fibrinogen levels improved in the first week in all patients. In the second week, two patients developed bleeding as a result of primary fibrinolysis. It is concluded that Org 10172 may be useful in the treatment of patients with DIC. In patients with APL, inhibition of DIC will be insufficient to control all bleeding, since primary fibrinolysis may also occur.

Acute promyelocytic leukemia. M.D. Anderson Hospital experience

Sixty patients with acute promyelocytic leukemia were treated between 1973 and 1984. The overall median survival was 16 months with a five-year survival rate of 31 percent. The complete remission rate was 53 percent and was similar whether they received amsacrine- or anthracycline-based regimens (60 percent versus 51 percent). The median remission duration was 29 months. At five years, 43 percent of patients with responses to treatment had continuous remission and 57 percent were alive. Salvage therapy produced remissions in 53 percent of patients during first relapse, with two long-term survivors after further consolidation with bone marrow transplantation. Early fatal hemorrhage associated with disseminated intravascular coagulopathy during induction therapy occurred in 16 patients (26 percent). Multivariate analysis of the pretreatment patient characteristics significantly associated with an increased risk of fatal hemorrhage identified four that have primary prognostic importance: thrombocytopenia, elevated absolute blast and promyelocyte counts, old age, and anemia. Patients having up to two unfavorable features had a low risk of fatal hemorrhage compared with those who had more than two (5 percent versus 58 percent; p less than 0.0001). Overall, patients who received heparin had a lower incidence of fatal hemorrhage than those who did not (19 percent versus 32 percent). Heparin therapy was not beneficial to those at low risk but was associated with a trend towards decreased hemorrhagic deaths among high-risk patients (45 percent versus 67 percent). Cytogenetic studies demonstrated the characteristic 15;17 translocation in 73 percent of patients with analyzable metaphases, whereas 12 percent had other karyotypic abnormalities. Remission induction was often associated with a gradual atypical morphologic evolution into remission without intermediate hypoplasia with the interim marrows showing a high proportion of blasts. It is concluded that acute promyelocytic leukemia is a unique disease with a high potential for cure. Knowledge of its prognosis using present frontline and salvage therapy, of the factors related to fatal hemorrhage, and of the unusual patient marrow profiles during remission induction may improve the therapeutic approach.

Factors and inhibitors of blood coagulation and fibrinolysis in acute nonlymphoblastic leukaemia

Factors of coagulation and fibrinolysis have been evaluated in 15 patients with untreated acute nonlymphoblastic leukaemia (ANLL). 10 patients had major bleeding (MB) and 6 had laboratory signs of DIC. 5 patients went into complete remission (CR). Antithrombin III (AT III) was decreased in 7 patients, antiplasmin (AP) in 9, fibronectin (FN) in 6 and factor XIII in 4/12. The ratio between factor VIIIR:Ag and factor VIII:C was over 2.0 in 11 patients, and high values were especially seen in patients with MB and patients with DIC. Spontaneous proteolytic activity, measured with S-2288 was increased in 3 patients who all had MB, and none of whom achieved CR. 2 patients with promyelocytic leukaemia (M3) had low fibrinogen and AP, high FDP and normal AT III, speaking for primary fibrinolysis, which in addition to proteolytic enzymes in the blast cells are important contributing factors regarding MB in ANLL.

Acute promyelocytic leukemia in 57 previously untreated patients

Fifty-seven patients in initial phase of acute promyelocytic leukemia (APL) were treated in the same department with heparin infusion, platelet transfusions, and two related induction regimens both including cytosine arabinoside and daunorubicin. Clinical and biological findings at presentation were studied. The complete remission (CR) rate was 53%. Twenty-seven patients (47%) died during the initial course of the disease, either before day 5 (early death [ED], n = 7) or after day 5 (death in aplasia [DA], n = 20). Most ED was due to intracerebral hemorrhage (6/7), especially when large hemorrhages had been seen on fundus oculi examination. Most DA was due to multivisceral failure (9/20). No correlation was found between initial disseminated intravascular coagulation (DIC) and death. However, the worsening of coagulation parameters during induction therapy, with or without initial DIC, significantly increased the occurrence of renal and respiratory failure which were particularly frequent during the first month. The median duration of survival was short (3.5 months) and the median duration of CR (11 months) was similar to that of other acute myeloid leukemias treated with the same regimens. The possible causes of the high mortality observed during the initial courses of APL and the possible benefit of a more graduate induction chemotherapy are discussed.

Controversies in the therapy of acute myelogenous leukemia

In the past 10 years, there has been substantial progress in the treatment of patients with acute myelogenous leukemia. Intensive induction chemotherapy and consolidation chemotherapy have increased complete remission rates from 25 percent to more than 70 percent and have extended median survival from six months to more than two years. Attempts to prolong remission with maintenance chemotherapy, immunotherapy, and central nervous system prophylaxis have been less successful. Recent data suggest that the use of intensification chemotherapy or bone marrow transplantation in patients in remission may further reduce or eliminate residual leukemia. As a result of one or more of these advances an increasing proportion of patients, up to 25 percent in some series, are alive and free of disease three to five years following diagnosis. Most data indicate that some of these patients may be cured. In this article, we review the therapeutic interventions responsible for this substantial increase in survival in what was previously a uniformly fatal disease. Recent advances are discussed as are controversies in management and future directions.