Acute Myeloid Leukemia (AML)

Carolyn Vachani, RN, MSN, AOCN
The Abramson Cancer Center of the University of Pennsylvania
Last Modified: September 8, 2011

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This article is a more specific discussion of AML. Please be sure to read Leukemia: The Basics first, so you have a basic understanding of leukemia.

What is AML?

AML is a blood cancer that affects white blood cells, red blood cells, and/or platelets. A person with AML develops abnormal numbers of these cells very quickly, giving the disease the name "acute". The white blood cell (WBC) count may be higher or lower than normal, but the WBCs that are being produced do not function well. Because WBCs are an important part of fighting infections, patients often have multiple infections that don't respond to treatment before they are diagnosed. Some people will have low red blood cell or platelet counts, but this is not always the case.

There will be an estimated 12,330 cases diagnosed in 2010 in the United States, accounting for over 30% of all leukemia cases. AML can occur at any age, but is more common in adults, particularly over age 50, with the average age at diagnosis being 67 years. The incidence of AML increases with age and is slightly more common in men than in women with a male to female ratio of 5:3.

What causes AML?

Although we do not know what causes every case of AML, there are certain exposures that can increase risk. Exposure to ionizing radiation, such as from an atomic bomb or working in the nuclear industry, increases risk slightly (the increase has been seen in nuclear workers, but not people living near nuclear plants). Exposure to benzene increases the risk of developing AML. Smoking cigarettes is the most common way people are exposed to benzene, although some may be exposed to this chemical in their jobs. A history of blood or genetic disorders, such as myelodysplasia, Fanconi's Anemia, NF1 and Li Fraumeni syndrome all increase the risk of developing AML. Risk is also increased in children with Down's Syndrome (trisomy 21). There is an increased risk for people with a first-degree relative (parent, sibling, child) with the disease.

Previous treatment with chemotherapy or radiation can lead to AML, which is often called treatment-related AML and thought to account for between 10 and 20% of AML cases. The risk is thought to be most strongly associated with certain chemotherapy agents. Risk after radiation treatment alone, given without these chemotherapy agents, is relatively low. In the case of alkylating agents (ifosfamide, cisplatin, melphalan, cytoxan, etc.), AML most often occurs 5 to 7 years after exposure to the chemotherapy (known as a "latent period"), and tends to start as myelodysplastic syndrome, which is a bone marrow disorder that results in abnormal blood cell counts. AML caused by treatment with alkylating agents carries a poor prognosis, as the disease is often not responsive to treatment.

A second category of treatment-related AML are those cases caused by a group of medications called topoisomerase II inhibitors, which include etoposide, doxorubicin, daunorubicin and mitoxantrone. These cases generally occur less than 3 years after treatment with the agent. Unfortunately, they are also not very responsive to therapy and carry a poor prognosis.

How do people with AML present?

In AML, certain blood cells do not fully mature and cannot function properly. These immature cells, called "blasts", also suppress normal blood cells from forming and further compound the problem. Symptoms are related to the abnormal numbers and function of blood cells and can include fever, infection, easy bleeding or bruising, shortness of breath, or weakness. These symptoms can also be signs of common illnesses like the flu and it is not uncommon for a person to be seen several times by a healthcare provider before receiving a diagnosis of AML. Most infections are just infections and not leukemia, so treating a suspected infection is appropriate and this short delay in diagnosis is not likely to affect the course of the disease. What is important is that a person returns to their physician for further investigation if the symptoms they have are not responding to the prescribed treatment (often antibiotics).

AML is most often discovered when a person has an infection that does not improve with treatment or unexplained bleeding or bruising and a blood count is checked, with abnormal counts or blasts seen on the results. Once this occurs, further testing is required to determine the type of AML.

What happens once someone is suspected of having AML?

Once AML is suspected, further blood tests may be drawn and a bone marrow biopsy and aspiration performed to better classify the AML. There are two classification systems for AML. The FAB (French American British) classification, which is the older of the two (see chart below), classifies based on the type of affected cell and how much it looks like normal cells (called differentiation). The FAB system requires the presence of >30% blast cells in the bone marrow to assign a diagnosis of AML.

The World Health Organization classification of AML uses genetic abnormalities to classify categories of AML. This system changed the threshold for diagnosis of AML to >20% blast cells in the bone marrow and groups various subtypes of AML based on genetic abnormalities and prognosis. Depending on the system used, a patient may hear their AML described by a FAB classification (M something), a full name (such as acute myelomonocytic leukemia) or by genetic abnormalities (such as an 8; 21 translocation). (See classification systems below.)

Patients with AML may have abnormalities detected in certain genes, which gives the physician some information about prognosis. Patients can be classified into prognostic risk groups (favorable, intermediate and poor) based on the genetic abnormalities present, which may help determine the most appropriate course of therapy. For example, the FLT3 mutation involves a membrane receptor that stimulates cell proliferation; when FLT3 has a mutation called an internal tandem duplication, this receptor is always “on”. The presence of such a mutation is associated with higher rates of relapse and poorer survival. Favorable characteristics include T(15;17), an inversion in chromosome 16 without a c-Kit mutation, a t(8;21) without a deletion in 9q, and many more combinations which will not be listed here.

If the patient is experiencing any neurologic symptoms at the time of diagnosis (headache, change in mental status, confusion, etc.), a lumbar puncture and/or CT scan or MRI of the head may be performed to see if leukemia cells are present in the spinal fluid. In some cases, CT scans or x-rays may be used to evaluate leukemia involvement in other organs. All patients who will receive anthracycline chemotherapy (idarubicin or daunorubicin) will require a test to evaluate cardiac function called a MUGA (Multiple Gated Acquisition) Scan prior to starting therapy to determine that their heart can tolerate the therapy and to establish a baseline to compare to if future chemotherapy is needed or the chemotherapy causes any damage to the heart.

FAB Classification of AML

Subtype (Number) and percent of all AML cases

Subtype (Name)

Commonly Associated Genetic Abnormalities

M0 (˜3% of all AML cases)

Acute undifferentiated leukemia

t(10;11) (called 10 11 translocation)

M1 (15-20%)

AML with minimal differentiation (or myeloblastic)

t(10;11) (called 10 11 translocation) Trisomy 11

M2 (25-30%)

AML with differentiation (or myeloblastic)

t(8;21) (called 8 21 translocation)

M3 (5-10%)

Acute promyelocytic leukemia

t(15;17) (called 15 17 translocation)
t(11;17) t(5;17)

M4 (20-30%)

Acute myelomonocytic leukemia

Inversion 16 t(6;11)

M5 (2-9%)

Acute monoblastic leukemia

t(9;11) t(6;11)

M6 (3-5%)

Acute erythroid leukemia

t(3;5)

M7 (3-5%)

Acute megakaryocytic leukemia

t(1;22)

M8

Acute basophilic leukemia (accounts for only 1% of all AML cases)

 

WHO Classification

The World Health Organization classification is complex and difficult for the novice patient to understand, but it is provided here because you may hear your team discussing your leukemia using this system. If you would like to learn more, visit the NCI's health professional information on the WHO system.

WHO Classification

AML Cytogenetic Abnormalities Within The Classification (Related FAB Classifications)

Acute myeloid leukemias with characteristic genetic abnormalities (generally considered favorable prognosis except for 11q23 abnormalities)

AML with t(8;21)(q22;q22) (AML1/ETO) (FAB M2)

AML with inv(16)(p13q22) or t(16;16)(p13;q22) (CBF?/MYh41)

Acute promyelocytic leukemia [FAB M3, AML with t(15;17)(q22;q12) (PML/RAR?) and variants]

AML with 11q23 (MLL) abnormalities

Acute myeloid leukemia with multilineage dysplasia

AML evolving from an MDS (Myelodysplastic Syndrome)

AML following an MDS

Acute myeloid leukemia and myelodysplastic syndrome, therapy related
(generally considered poor prognosis)

Alkylating agent related

Topoisomerase II inhibitor related

Acute myeloid leukemia not otherwise categorized

AML minimally differentiated (FAB M0)

AML without maturation (FAB M1)

AML with maturation (FAB M2)

Acute myelomonocytic leukemia (FAB M4)

Acute monoblastic and monocytic leukemia (FAB M5a and M5b)

Acute erythroid leukemia (FAB M6)

Acute megakaryoblastic leukemia (FAB M7)

Acute basophilic leukemia

Acute panmyelosis with myelofibrosis

Myeloid sarcoma

Acute leukemia of ambiguous or undetermined lineage
(generally considered poor prognosis)

Undifferentiated acute leukemia

Bilineal acute leukemia

Biphenotypic acute leukemia

How is AML treated?

For many years, AML has most commonly been treated initially with a combination of two chemotherapy agents, cytarabine (for 7 days) and either daunorubicin or idarubicin (for 3 days). This regimen is sometimes called 7+3 for the days the medications are given over. This initial treatment is called "induction chemotherapy" and attempts to induce a remission. If remission does not occur, induction chemotherapy can be repeated or a new chemotherapy regimen tried. Once a remission is achieved, which is defined as <5% blast cells seen in the bone marrow, chemotherapy is continued for 4-5 more cycles (4-6 months), generally with cytarabine alone, in higher doses. This treatment after remission is achieved is called "consolidation chemotherapy".

While it sounds simple, the treatment is designed to wipe out the abnormally functioning leukemia cells, but this treatment also destroys many healthy cells as well, putting the patient at risk for bleeding and infection, which can be life threatening. In addition, the chemotherapy medications can cause side effects such as mouth sores, diarrhea, nausea/vomiting and hair loss. Some patients may be candidates for autologous or allogeneic stem cell transplants.

In the seventies, the 5-year survival among those newly diagnosed was under 10%. This has improved, particularly among those under age 55, to nearly 40%. Patients under age 55 tend to do better than those over 55.

In the last 10 years there have been substantial changes to the AML treatment protocols for elderly patients (who are often too ill to receive the standard therapy) and for patients with APML [also called M3 or t(15;17)], which is treated differently than other subtypes. Let's address these special circumstances.

Elderly Patients

In general, we consider patients "elderly" from age 55-60 and older. This is not to say that all 60 year old people are "elderly." This classification came about because patients over 60 have been found to have poorer response to standard therapy, regardless of their overall health. This may be a result of yet unidentified genetic abnormalities in these patients. So, given that these patients are less likely to respond to the standard treatment, or are not candidates for an intensive regimen due to their health, some centers are using alternative regimens or clinical trials in elderly patients, particularly those with genetic changes associated with poorer prognosis.

Mylotarg (gemtuzumab ozogamicin) is a type of targeted therapy that is no longer approved for use by the U.S. FDA. It was withdrawn from market in June 2010 when a clinical trial (SWOG S0106 ) showed the drug increased patient death and added no benefit over conventional cancer therapies. Some of the less intensive regimens being studied include: cytarabine at low doses given once or twice a day by injection under the skin (subcutaneous, like insulin is given), clofarabine monotherapy, autologous or allogeneic (reduced intensity) stem cell transplant and various clinical trials. Some patients who cannot tolerate any therapy may be offered supportive care only, which is not active treatment, but attempts to maintain quality of life for the patient.

Acute Promyelocytic Leukemia (APL or APML)

APL (or M3) is a type of AML whose treatment has changed dramatically in the past 20 years. Previously one of the most malignant forms of AML, this subtype is now considered curable in many patients. In the 1970s and 80s, researchers discovered an abnormal protein in cells, which is caused by the 15;17 translocation (genetic abnormality) and leads to the development of APML. This abnormal protein prevents the immature blood cells from differentiating (or progressing) into functioning, mature cells. A drug called all-trans retinoic acid (ATRA) allows these immature cells (also called blasts) to mature and die. ATRA is given in combination with an anthracycline chemotherapy (daunorubicin or idarubicin) as induction and consolidation chemotherapy for APML. In addition, arsenic trioxide is being used for patients who do not achieve a remission with ATRA based therapy and being studied as an alternative to chemotherapy in the ATRA regimen.

APML is often associated with a condition of bleeding and blood clotting called DIC (or disseminated intravascular coagulation). In DIC, the body is making blood clots where it should not and rapidly using up the components necessary for blood clotting, which leads to bleeding at the same time as these clots are being formed. Patients with this complication will require various blood product transfusions and emergent treatment of the leukemia. The condition is a result of the leukemia, so it must be treated in order for the DIC to resolve.

Complications & Concerns of Leukemia and Treatment

Leukocytosis

Some people with AML will present with a very high white blood cell count, which is called leukocytosis and can cause symptoms for the patient, including headache, shortness of breath and chest pain. In some cases, chemotherapy will be started right away to lower the white blood cell count, but in other cases, it may take a few days to clarify the diagnosis or complete the pretreatment testing (bone marrow biopsy, evaluate heart function). For those patients, leukopheresis may be performed while the testing is completed. This is a procedure that removes white blood cells from the blood and returns the rest of the blood to the patient (it is similar to dialysis). Some centers may administer a chemotherapy called hydrea that lowers the white blood cell count also, although there is some controversy as to which method is more effective. Either is a temporary reduction in the WBC count, which without further chemotherapy will continue to rise.

Complications of treatment

People with leukemia are at risk of infection (due to few and poorly functioning white blood cells) and bleeding (due to low numbers of platelets) even before any therapy is started. Because these abnormalities are a result of the leukemia, it is necessary to treat the leukemia in order to correct the abnormal blood counts. Leukemia treatment causes the blood cell counts and function to temporarily get worse. During this time, patients will receive blood and platelet transfusions, antibiotics and take precautions to prevent infection and bleeding.

Hand washing is the single best way to prevent infection and should be performed frequently by patients, visitors, caregivers and healthcare personnel. Even the best hand washers get infections, so we implement a few other restrictions to help in the cause. People with leukemia cannot receive or consume fresh fruit, vegetables or flowers while in the hospital. (See the gift guide for ideas on what to send a patient with these restrictions) You may think this sounds odd, but these items can harbor bacteria and may put the patient at higher risk of infection. We ask people who are sick (or who have sick family members at home) not visit the patient in person and if they absolutely must, they need to wear a mask and wash their hands well.

In most cases, some type of infection or fever is inevitable. When this happens, the patient will typically have several tests done to look for a source of the infection, including blood, urine and stool cultures and a chest x-ray. Antibiotics will be started or adjusted if they are already being given. Many times the source of the infection is never identified and general antibiotics that treat a variety of things will be used. The patient will receive these antibiotics until their white blood count reaches a level that will allow them to fight the infection on their own.

Over the course of their treatment, patients will require either blood (for low hemoglobin levels) or platelet (for low platelet counts) transfusions. People with low hemoglobin counts (also called anemia) can experience fatigue, shortness of breath or appear pale. A low platelet count (also called thrombocytopenia) can lead to bleeding. This can be as small as gums bleeding when brushing the teeth or a nosebleed to dangerous bleeding, such as a stroke. Patients should use caution to avoid bumping themselves with normal activities; they may not shave with a razor (electric razor is okay, with caution) and should avoid any activities that increase the risk of bleeding or bruising. Patients should always inform their healthcare team if they have symptoms of anemia or thrombocytopenia.

A diagnosis of leukemia is very scary, but understanding what is happening and what to expect can help alleviate some anxiety. Learning about the treatments, potential side effects, and how the healthcare team will manage them can help patients and their caregivers, friends, and family.

References

Abeloff, M., Armitage, J., Niederhuber, J., Kastan, M. & McKenna, G. (Eds.): Clinical Oncology (2004). Elsevier, Philadelphia, PA.

The American Cancer Society. Facts and Figures 2007. www.cancer.org

Breitenbucher, F., Schnittinger S., Grundler R., et al Identification of a novel type of ITD mutations located in nonjuxtamembrane domains of the FLT3 tyrosine kinase receptor Blood 2009; 113:4074-4077.

Burnett, A. K. and U. Mohite (2006). "Treatment of older patients with acute myeloid leukemia--new agents." Semin Hematol 43(2): 96-106.

Estey, E. and H. Dohner (2006). "Acute myeloid leukaemia." Lancet 368(9550): 1894-907.

Hoffman, R et al. (Eds): Hematology Basic Principles and Practice (2005). Elsevier, Philadelphia, PA.

Kolitz, J. E. (2006). "Current therapeutic strategies for acute myeloid leukaemia." Br J Haematol 134(6): 555-72.

Petersdorf S, et al. SWOG S0106: Phase III Randomized Trial of GO in induction and Maintenance in Untreated AML. ASH 2009 Abstract 790.

Sanz, M. A. (2006). "Treatment of acute promyelocytic leukemia." Hematology Am Soc Hematol Educ Program: 147-55.

Sanz, M. A., M. S. Tallman, et al. (2005). "Practice points, consensus, and controversial issues in the management of patients with newly diagnosed acute promyelocytic leukemia." Oncologist 10(10): 806-14.

National Cancer Institute

The Leukemia & Lymphoma Society

SEER Stat Fact Sheets: Acute Myeloid Leukemia



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