Acute myeloid leukemia overview

Acute myeloid leukemia (AML), also called acute myelogenous leukemia, is an aggressive, fast-growing form of blood cancer that starts in immature cells that would normally give rise to certain types of blood cells. These abnormal cells multiply rapidly, crowding out healthy blood cells and leading to symptoms such as fatigue, infections, and easy bleeding.

Considering each component of its name helps reveal what AML is. It is a type of leukemia, a cancer that begins in the bone marrow, the spongy tissue inside some bones where blood cells develop. It is acute, meaning that it progresses rapidly. And it starts in myeloid progenitor cells, the precursors to red blood cells, platelets, and certain white blood cells.

AML is the most common acute leukemia in adults, although it can occur at any age, including in children. The American Cancer Society estimates that more than 22,000 people in the U.S. will be diagnosed with AML in 2026, accounting for about 1% of all new cancer diagnoses.

Causes and risk factors

AML occurs when the accumulation of various genetic mutations causes myeloid progenitor cells to multiply uncontrollably in the bone marrow instead of maturing into healthy blood cells. The exact cause of AML is usually unknown, but researchers have identified several factors that can increase a person’s risk of developing the disease.

Factors associated with an increased risk of AML include:

• Inherited genetic changes: Certain gene changes and chromosome disorders inherited from a person’s biological parents can increase AML risk.
• Acquired genetic changes: DNA mutations that develop during a person’s lifetime play a key role in most cases of AML.
• Preexisting conditions: Certain blood and bone marrow disorders can develop into AML, and some autoimmune conditions have been linked to a greater risk of AML.
• Environmental exposures: Long-term exposure to certain chemicals (particularly benzene), cigarette smoke, and environmental radiation can increase the risk of developing AML.
• Previous cancer treatment: Certain chemotherapy drugs and radiation therapy can increase the risk of therapy-related AML occurring years later.
• Demographic factors: AML is more common in older adults and occurs slightly more often in males than females; having a close relative with AML also increases a person’s chances of developing the disease.

Precursor bone marrow disorders

Some blood and bone marrow disorders can progress to AML over time. These include:

• Myelodysplastic syndrome (MDS): This group of disorders occurs when blood stem cells fail to mature into healthy blood cells.
• Myeloproliferative neoplasms (MPNs): These chronic blood cancers cause the bone marrow to produce too many blood cells. MPNs include myelofibrosis, essential thrombocythemia, and polycythemia vera, all of which can evolve over time into AML.
• Chronic myeloid leukemia: This slow-growing blood cancer that also affects myeloid cells can sometimes transform into acute leukemia.

Doctors may recommend regular testing for people with these bone marrow conditions. That can help catch progression to AML earlier, which may improve treatment outcomes.

Subtypes

There are different AML subtypes, and identifying which one a person has is an important part of the diagnostic process. Doctors also use this information to estimate prognosis, guide treatment decisions, and determine whether more or less intensive therapy is appropriate.

To classify AML, doctors generally use one of two internationally recognized systems. The most widely used comes from the World Health Organization (WHO) and primarily classifies AML based on genetic changes found in leukemia cells and, in some cases, how mature the abnormal cells are.

In this system, AML may be broadly categorized as:

• AML with defining genetic abnormalities: These cases are characterized by specific gene mutations or chromosome changes that help identify distinct disease subtypes.
• AML defined by differentiation: These cases lack defining genetic abnormalities and are instead classified based on how mature or immature the leukemia cells appear under the microscope.

Some AML subtypes are associated with genetic changes, such as NPM1 or KMT2A abnormalities, that can influence prognosis and help determine whether targeted therapies may be an option. Because of this, accurately identifying a person’s AML subtype is an important step in developing an individualized treatment plan.

Another commonly used classification system is the International Consensus Classification (ICC). Like the WHO classification, it incorporates genetic findings but also considers certain clinical features to further define AML subtypes.

Symptoms

Because leukemia cells rapidly crowd out healthy blood cells in the bone marrow, AML signs and symptoms often develop suddenly over a short period, usually days or weeks, and become worse over time.

Common AML symptoms may include:

• general weakness
• fatigue
• dizziness or lightheadedness
• headache
• fever
• frequent infections
• easy bleeding or bruising
• shortness of breath
• unexplained weight loss
• joint or bone pain
• a feeling of fullness in the abdomen
• paleness (pallor)
• swollen lymph nodes

Many of these symptoms are caused by low numbers of healthy red blood cells, white blood cells, or platelets. While these signs can resemble those of other illnesses, reporting them early to a doctor is the best way to ensure a prompt diagnosis and improve the success of AML treatments.

Diagnosis

If a healthcare provider suspects AML based on symptoms or abnormal blood test results, several tests may be needed to confirm a leukemia diagnosis and determine the specific subtype. Among such tests are:

• a detailed medical history and physical examination that can help identify symptoms and risk factors, and look for physical signs of disease
• a complete blood count (CBC), which is a standard blood test that measures the number of different types of blood cells and may reveal abnormal blood counts
• a bone marrow aspiration or biopsy, in which a small sample of bone marrow is removed, usually from the hip bone, to identify cancerous cells and determine the type of leukemia a person has

After AML is confirmed, additional laboratory testing is performed on blood or bone marrow samples to identify genetic abnormalities and other features of the leukemia that may inform treatment planning. For example, people with specific proteins or DNA abnormalities in their cancerous cells may be eligible for certain targeted therapies.

The diagnostic process may also include tests to evaluate general fitness or how well a person’s kidneys, liver, heart, and other organs are working. This will help determine whether certain treatments are likely to be well tolerated.

Classification

Unlike many other cancers, AML is not assigned stages based on tumor size or whether it has spread. Instead, doctors may refer to broad categories of disease progression and treatment, which include:

• newly diagnosed, which refers to AML that has not yet been treated
• in remission, in which very few leukemia cells remain in the bone marrow, blood counts have returned to normal, and there are no signs or symptoms of disease
• refractory, which is AML that does not respond adequately to treatment
• relapsed, in which the disease returns after a period of remission.

Treatment

Treatment for AML usually begins soon after diagnosis, and involves two or three stages:

• induction, which aims to rapidly eliminate most leukemia cells and induce remission
• consolidation, which aims to destroy any residual cancerous cells and prevent the cancer from coming back
• maintenance, which aims to reduce the risk of relapse and keep the cancer in remission for as long as possible

Induction and consolidation often require intensive treatments with potentially severe side effects. If someone with AML has other health problems or is otherwise unable to tolerate these types of treatments, doctors may recommend a less intensive, safer approach.

Maintenance is generally reserved for people at higher risk.

Treatment overall often includes one or more of the following approaches:

• Chemotherapy: These are medications that kill leukemia cells or stop them from growing.
• Targeted therapy: These treatments target specific specific genetic changes or other features of AML.
• Stem cell transplant: This procedure removes existing blood stem cells and replaces them with healthy stem cells, usually from a donor, which can then produce healthy blood cells.
• Radiotherapy: Used only in specific situations, such as alongside chemotherapy, this treatment prepares patients for a stem cell transplant; it’s also used when leukemia has spread outside the bone marrow.
• Supportive care: These treatments help manage symptoms, reduce medication side effects, and maintain quality of life.

AML prognosis and survival rate

Although AML is an aggressive disease, survival rates have improved over the past several decades due to advances in supportive care, stem cell transplants, and targeted therapies. About one-third of people with AML in the U.S. now live five years or more after being diagnosed.

Still, it is important to keep in mind that outcomes vary widely from person to person depending on various factors. For example, the prognosis of AML is typically better if a patient:

• is younger
• has mutations with favorable risk profiles
• has lower white blood cell counts in the blood at diagnosis, indicating less advanced disease
• does not have a history of chronic leukemia or MDS
• has not been exposed to radiation or chemotherapy for prior cancers
• reaches remission more quickly
• does not relapse

A healthcare team can provide the most accurate information about prognosis based on a person’s specific disease characteristics and response to treatment.

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