ACUTE PROMYELOCYTIC LEUKAEMIA

UNIT V PRESENTATION

• Acute promyelocytic leukemia (APL) is a unique subtype of the acute leukemias.

• It has distinct cytogenetics, clinical features, and biologic characteristics. Acute promyelocytic leukemia (APL) is caused by an arrest of leukocyte differentiation at the promyelocyte stage.

• The discovery and elucidation of the molecular pathogenesis for APL has led to the first and only targeted therapy for leukemia

HAEMATOPOIESIS

(PSC-MSC-myeloblast-promyelocyte – metamyelocyte – myelocyte -PMN

EPIDEMIOLOGY

• AML comprises 11% of the cases of leukemia in childhood in the United States, with approximately 380 children diagnosed with AML annually.

• APL is more common in certain other regions of the world, but incidence of the other types is generally uniform.

• Affects males and females equally• Several chromosomal abnormalities associated with

AML are identified, but no predisposing genetic or environmental factors can be identified in most patients

Prognosis

• Very good survival rates (up to 90% molecular remmission) in developed countries where cytotoxics are given together with retinoic acid (ATRA)

• Still very poor in our setting

PATHOGENESIS

• Acute myelogenous leukemias, characterized by the accumulation of immature myeloid forms in the bone marrow and the suppression of normal hematopoiesis

• Most AMLs are associated with acquired genetic alterations that inhibit terminal myeloid differentiation. As a result, normal marrow elements are replaced by relatively undifferentiated blasts exhibiting one or more types of early myeloid differentiation

• Acute promyelocytic leukemia (APL) is defined by its cytogenetic properties. Over 95% of cases are characterized by a balanced translocation between chromosome 17q21 and chromosome 15q22.

• This leads to an abnormal fusion protein called PML-RAR alpha

• In APL the translocation occurs between genes that would normally help to restrict tumor growth and help white blood cells to mature in a healthy way.

• When these genes trade places, a mutant gene is formed.

• This mutant gene encodes for a protein that prevents maturation of the promyelocyte

CLASSIFICATION OF APL

• It is classified as AML M3 by the old French-American-British (FAB) system

• Acute promyelocytic leukemia (APL) with translocation between chromosomes 15 and 17, ie t(15;17) in the World Health Organization (WHO) classification system.

FAB vs WHO• FAB classification is the most widely used system in current use where AML is

divided into eight (M0 to M7) categories.This scheme takes into account both the degree of maturation (M0 to M3) and the lineage of the leukemic blasts (M4 to M7).

• The FAB classification categorized leukemia based on cell morphology, including cytochemical stains, whereas the WHO system also includes flow cytometry, cytogenetic studies and, in some cases, clinical information.

• A recently proposed WHO classification for AML retains the FAB categories M0 to M7 but also creates special categories for AMLs associated with particular chromosomal aberrations (e.g., the t(15;17), t(8;21), inv(16), or 11q23 rearrangements), which arise after prior chemotherapy or follow a myelodysplastic syndrome.

• This classification thus attempts to define forms of AML according to molecular pathogenesis and outcome. Given the increasing role of cytogenetic and molecular features in directing therapy, a further shift toward molecular genetic classifications of AML seems inevitable and desirable

WHO classification

CLINICAL FEATURES - leukemias

• The production of symptoms and signs of AML, is due to replacement of bone marrow by malignant cells and to secondary bone marrow failure.

• Thus, patients with AML may present with any or all of the findings associated with marrow failure.

History is rather short

• Short (<3-month) history of symptoms due to bone marrow failure (e.g. of anaemia, abnormal bruising/bleeding or infection).

• DIC with bleeding is particularly common in acute promyelocytic leukaemia

• Increased cellular catabolism may cause sweating, fever and general malaise.

• Lymphadenopathy and hepatosplenomegaly are less frequent than in ALL

• Tissue infiltration of skin, bones, gums with hypertrophy (AML M5 or M4).

• Initially there are non-specific symptoms are present for less than 3 mo

• As the disease progresses, signs and symptoms of bone marrow failure become more obvious with the occurrence of pallor, fatigue, bruising, or epistaxis, as well as fever, which may be caused by infection.

• On physical examination, findings of pallor, listlessness, purpuric and petechial skin lesions, or mucous membrane hemorrhage may reflect bone marrow failure

AML clinical features

• subcutaneous nodules or “blueberry muffin” lesions, infiltration of the gingiva, signs and discrete masses, known as chloromas or granulocytic sarcomas.

• Patients can present with neurologic deficits or headaches if there is central nervous system (CNS) involvement.

APL• In APL is set apart from other forms of AML many patients present

with coagulopathy. The coagulopathy has been described as DIC with associated hyperfibrinolysis.

• APL has been associated with– low levels of plasminogen, – Low levels alpha2-plasmin inhibitor, and – plasminogen activator inhibitor 1 found in fibrinolytic states.

• There is increased expression of annexin II, a receptor for plasminogen and plasminogen-activating factor, on the surface of leukemic promyelocytes.This leads to overproduction of plasmin and fibrinolysis.

• It is important to treat the coagulopathy as a medical emergency. In 40% of untreated patients, pulmonary and cerebral hemorrhages can occur.

DIAGNOSIS• FBC & DC – may be normal, may have low platelets and Hb but raised

WCC, or all the 3 celllines may be depleted (aleukemic leukemia). Anemia and thrombocytopenia may indicate bone marrow failure.

• Peripheral smear – blasts in the PS suggest a leukemic process. Occasionally, the peripheral smear might not contain any blasts (aleukemic leukemia). For this reason, bone marrow examination is essential to exclude acute leukemia in pancytopenic patients

• Bone marrow aspiration - When the results of an analysis of peripheral blood suggest the possibility of leukemia, a bone marrow examination should be done promptly to establish the diagnosis. – Bone marrow aspiration alone is usually sufficient, but sometimes a bone

marrow biopsy is needed to provide adequate tissue for study or toexclude other possible causes of bone marrow failure.

OTHER INVESTIGATIONS

• U & Es• LFTs• CSF studies – esp in hyperleukocytosis• Imaging studies- • Prothrombin time (PT) and activated partial

thromboplastin time (aPTT), fibrinogen measurements.

The diagnosis is based on finding that myeloid blasts make up more than 20% of the cells in the

marrow• Several types of myeloid blasts are recognized. • Myeloblasts have

– delicate nuclear chromatin – two to four nucleoli– more voluminous cytoplasm than lymphoblasts – The cytoplasm often contains fine, azurophilic, peroxidase-

positive granules. Distinctive red-staining peroxidase-positive structures called Auer rods, which represent abnormal azurophilic granules, are present in many cases and are particularly numerous in AML associated with the t(15;17).

• The presence of Auer rods is taken to be definitive evidence of myeloid differentiation

promyeloblast

Histologic variants of APL

• The hypergranular subtype (classic M3) has frequent Auer rods, clumps of granular material containing lysosomes, peroxidase, lysosomal enzymes, and large crystalline inclusion. The nucleus is folded or bilobed, and the cytoplasm contains prominent azurophilic granules. The bone marrow is usually hypercellular. The cells stain intensely for Sudan black and myeloperoxidase, but not for periodic acid-Schiff (PAS) and HLA-DR.

• The microgranular variant (M3v) also has a folded nucleus, but the cytoplasm has fine, dusky granules and Auer rods are rare. It is seen in 25% of cases

• The hyperbasophilic subtype shows an increased nucleocytoplasmic ratio and strongly basophilic cytoplasm with blebs. There are few granules and no Auer rods.

• The last variant is PLZF-RAR alpha (M3r), and it has regular, condensed chromatin in the nucleus. There are fewer granules and rare Auer rods when compared with the hypergranular subtype

• BM aspirate samples can be sent for flow cytometry, cytogenetics or FISH for the usual translocations.

• The typical phenotype of acute promyelocytic leukemia (APL) is myeloperoxidase positive and CD33 positive, human leukocyte antigen (HLA)-DR negative.

PROCEDURE

• BONE-MARROW ASPIRATION– Informed consent needed– Sterile procedure– Pt lies prone on abd– 1% lignocaine is used to

numb the area– Using special bone marrow

aspiration needle– Posterior superior iliac

spine, or sternum

Bone marrow aspiration• An aspirate needle is inserted through the skin and forced down till it

abuts the bone

• The clinician the advences the needle though the bony cortex into the marrow cavity by a twisting motion of the hand

• Once the needle is in the cavity, the needle is removed and a syringe is attached and used to aspirate marrow

• Some of the aspirate is used to make slides and the remainder put into an EDTA bottle and sent to the lab for cytology

• Remember to give the patient analgesia

TREATMENT

• Patients with acute leukemia should be treated in centers staffed by specially trained physicians with access to adequate supportive care eg platelet transfusion and adequate nursing care.

• Patients need to be nursed in a sterile environment when their bone-marrow cells are depleted

• Access to a well equipped laboratory is also crucial.

• High-risk patients with acute promyelocytic leukemia (APL) (WBC >10,000/μL) should undergo induction and consolidation chemotherapy with an anthracycline (eg, idarubicin), cytarabine, and ATRA.

• ATRA should be started immediately to control coagulopathy.

• Chemotherapy can be started within 3 days, but it should be started as soon as possible for high-risk patients.

• Four small studies performed in China, India, Iran, and the United States at MD Anderson have investigated the role of ATO with ATRA as induction therapy with complete remission rates from 86-95%.

• However, a randomized controlled trial is needed to compare chemotherapy with ATRA versus ATO with ATRA to determine which therapy is ideal for induction.

ATRA

• ATRA was first demonstrated to be effective in acute promyelocytic leukemia (APL) in China during the mid 1980s.

• Pharmacologic doses of ATRA (45 mg/m2 divided into bid doses) led to terminal differentiation of malignant promyelocytes to mature neutrophils.

• However, ATRA alone cannot eradicate the malignant clone. There can be complete hematologic and molecular remission with the addition of chemotherapy to ATRA.

• studies have shown that extended ATRA treatment improved complete remission rates, improved overall survival, and reduced relapse rates.

ATRA induced differentiation

Other benefits

• ATRA helps to rapidly control the DIC associated with acute promyelocytic leukemia (APL).

Adverse effect - RAS

• About 25-50% of patients can develop retinoic acid syndrome (RAS) during treatment with ATRA

• This syndrome can occur within the first 21 days of treatment and is characterized by fever, hypotension, weight gain, respiratory distress, serositis with pleural or pericardial effusions, hypoxemia, radiologic infiltrates, acute renal failure, and hepatic dysfunction.

• Other side effects of ATRA include headache, nasal stuffiness, dry red skin and, rarely, pseudotumor cerebri.

• RAS should be treated with intravenous (IV) dexamethasone for at least 3 days.

• Resistance to ATRA has been seen with the other cytogenetics variants of acute promyelocytic leukemia (APL), especially the PLZF-RAR alpha mutation, but the resistance may also develop as a secondary event in garden variety APL.

Arsenic trioxide• ATO induces differentiation of acute promyelocytic leukemia (APL) cells

at low concentrations and apoptosis at higher concentrations by interacting with the PML-RAR alpha protein.

• ATO has been studied as part of induction therapy and in the relapsed setting.

• In 2004, Shen et al randomized 61 patients to ATRA versus ATO versus ATO and ATRA. All groups demonstrated high complete remission rates (>90%), but the combination group had the fastest time to complete remission, greater molecular reduction of disease, and lower relapse rates.

• However, ATO has not yet been compared to standard induction or consolidation chemotherapy in a randomized clinical trial. It is recommended that ATO is used in first-line setting if the patient cannot tolerate chemotherapy.

BONE MARROW TRANSPLANT

• The cure rate for acute promyelocytic leukemia (APL) is high, such that BMT is not the first option.

• There is also significant transplant-related mortality, especially with allogeneic transplants.

• BMT should be offered to patients in the relapsed setting.– Patients who achieve molecular remission with salvage therapy

should be offered high-dose chemotherapy, followed by autologous stem cell transplantation (SCT) for consolidation.

– Patients who have persistent molecular or hematologic disease after salvage therapy should be offered allogeneic SCT if they have a good performance status and an HLA-matched donor can be found.

So what is bone marrow transplant?

• Bone marrow transplantation (BMT) is a relatively new medical procedure being used to treat diseases once thought incurable. Since its first successful use in 1968, BMTs have been used to treat patients diagnosed with leukemia, aplastic anemia, lymphomas such as Hodgkin's disease, multiple myeloma, immune deficiency disorders and some solid tumors such as breast and ovarian cancer

• Although BMTs now save thousands of lives each year, 70 percent of those needing a BMT using donor marrow are unable to have one because a suitable bone marrow donor cannot be found.

• Large doses of chemotherapy and/or radiation are required to destroy the abnormal stem cells and abnormal blood cells found in cancers and aplastic conditions.

• These therapies, however, not only kill the abnormal cells but can destroy normal cells found in the bone marrow as well.

• A bone marrow transplant enables physicians to treat these diseases with aggressive chemotherapy and/or radiation by allowing replacement of the diseased or damaged bone marrow after chemo or radiation

• While bone marrow transplants do not provide 100 percent assurance that the disease will not recur, a transplant can increase the likelihood of a cure or at least prolong the period of disease-free survival for many patients.

How it is done• In a bone marrow transplant, the patient's diseased bone marrow is

destroyed and healthy marrow is infused into the patient's blood-stream.

• In a successful transplant, the new bone marrow migrates to the cavities of the large bones, engrafts and begins producing normal blood cells.

• If bone marrow from a donor is used, the transplant is called an "allogeneic" BMT, or "syngeneic" BMT if the donor is an identical twin.

• In cases where the disease afflicting the bone marrow is in remission or if the condition being treated does not involve the bone marrow, patients may be their own bone marrow donors, autologous BMT

• In an allogeneic BMT, the new bone marrow infused into the patient must match the genetic makeup of the patient's own marrow as perfectly as possible.

• Special blood tests are conducted to determine whether or not the donor's bone marrow matches the patient's.

• If the donor's bone marrow is not a good genetic match, it will perceive the patient's body as foreign material to be attacked and destroyed. This condition is known as graft-versus-host disease (GVHD) and can be life-threatening.

• Alternatively, the patient's immune system may destroy the new bone marrow. This is called graft rejection