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Acute myeloid leukemia (AML) is a cancer of the blood and bone marrow. In leukemia, cancer cells crowd out healthy blood cells, which can cause fever, fatigue, easy bruising, bleeding, infections, and other problems. Acute leukemia means that symptoms typically worsen over a short period of time. Children may become sick very quickly and need medical attention right away.
AML affects blood cells called myeloid stem cells. Normally, the bone marrow makes blood-producing stem cells that either become myeloid stem cells or lymphoid stem cells. A myeloid stem cell becomes one of three types of mature blood cells:
There are several subtypes of AML. This is important because the type of AML determines prognosis and treatment.
Knowing the subtype of AML allows doctors to classify AML cases into low-risk or high-risk, which helps them select the most appropriate treatment. Treatment for AML is usually chemotherapy and sometimes bone marrow transplant. Prescribing treatment based on risk category (risk-adapted therapy) has led to increased cancer survival rates. Patients with higher risk forms of cancer may receive the most aggressive therapy while patients with a lower-risk case may receive a lower-intensity treatment that has fewer side effects. For more information about AML subtype, ask your physician.
Subtypes of acute myeloid leukemia (AML) and related tumors seen in children (World Health Organization, 2016):
In AML, signs and symptoms may include:
Bone marrow tests are usually required to diagnose leukemia. Doctors may begin to suspect leukemia after conducting a physical exam, taking a medical history, and looking at the results of blood tests. Children with leukemia usually have a high number of immature white blood cells in their blood.
At first, a physician will perform a physical exam and look at the patient’s medical history. During the physical exam, the doctor will check general signs of health, including signs of disease, such as lumps or anything else that seems unusual. The eyes, mouth, skin, and ears will be looked at carefully. A nervous system exam may be done. The doctor will feel the patient’s abdomen for signs of an enlarged spleen or liver.
In looking at the patient's medical history, the doctor will look to see if there are any medical conditions or patterns of cancer in the family that could indicate that the cancer may be inherited. Only 8-10 percent of childhood cancers is inherited.
Risk factors for childhood AML include:
Complete blood count
Doctors will order a blood test called a complete blood count. A sample of blood is drawn and checked for the:
In leukemia, the blood may have a high number white blood cells. Many of these cells can be blasts, an early form of cell that is usually found only in the bone marrow in healthy children.
Blood chemistry studies
A blood sample is checked to measure the amounts of certain substances released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease.
Bone marrow tests like bone marrow aspiration and biopsy will confirm a diagnosis of cancer and pinpoint the type of cancer. Most children are asleep (sedated) during the procedure. If awake during the procedure, patients are given appropriate pain medicine.
Bone marrow aspiration: Doctors will obtain a bone marrow sample by inserting a thin, hollow needle into the hipbone. A pathologist will view the bone marrow under a microscope to look for signs of cancer.
Bone marrow biopsy: Doctors will remove a small piece of bone tissue to determine how much the cancer has spread in the bone marrow. The biopsy is typically performed right before or after the aspiration.
How is a bone marrow aspiration / biopsy performed?
If cancer is determined, more tests will be performed to pinpoint the subtype of the cancer. These tests include:
Immunophenotyping is used to diagnose specific types of leukemia by comparing the cancer cells to normal cells of the immune system.
Immunohistochemistry and flow cytometry are the laboratory tests.
Cytogenetic analysis involves laboratory tests in which pathologists look for certain changes in the chromosomes.
One such test is FISH (fluorescence in situ hybridization). This test looks at genes or chromosomes in cells and tissues. Pieces of DNA that contain a fluorescent dye are made in the laboratory and added to cells or tissues on a glass slide. When these pieces of DNA attach to certain genes or areas of chromosomes on the slide, they light up.
The doctor may recommend running laboratory tests to identify specific genes, proteins, and other factors involved in the leukemia. This examination is important because cancer is caused by mistakes (mutations) in the cell’s genes. Identifying these mistakes helps diagnose the specific subtype of leukemia. Based on that information, doctors can choose treatment options tailored to the individual case. Children whose leukemia shows mutations associated with a good outcome may be prescribed less toxic treatments. On the other hand, doctors may prescribe more intensive treatments for patients with a leukemia with mutations associated with poorer outcomes. Mutations may be identified for which a treatment targeted to that specific mutation are available.
Tests to determine if the cancer has spread include:
A lumbar puncture is performed to collect a sample of cerebrospinal fluid from the spinal column to determine if the cancer has spread to the central nervous system. This procedure is also called an LP or spinal tap.
A needle is placed between two bones in the spine and into the fluid around the spinal cord. A sample of fluid is removed. It is checked under a microscope for signs that leukemia cells have spread to the brain and spinal cord. Our bodies make spinal fluid constantly, so the body quickly replaces the small amount an LP takes.
An X-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body on a computer screen or special film. The chest X-ray is done to see if leukemia cells have formed a mass in the middle of the chest.
Doctors gather information to inform treatment.
The goal of this phase is destroy leukemia cells in the blood and bone marrow and bring the disease into remission.
Since AML patients are vulnerable to infection, supportive therapy with antibiotics is also given.
Central nervous system (CNS) sanctuary therapy (also called CNS prophylaxis) may also be given during this time to kill leukemia cells that remain in the brain and spinal cord.
Doctors will likely look at how well induction chemotherapy worked to decide if a hematopoietic cell transplant is needed. In fact, patients and families may undergo HLA typing to identify possible donors in case the patient needs to undergo a transplant.
Many pediatric centers use highly sensitive tests to measure for minimal residual disease (MRD). Positive MRD indicates a greater risk of relapse and need for more intensive therapy.
This consolidation phase begins after the patient is in remission. Its goal is to destroy any leukemia cells that may remain.
It includes 2-4 cycles of chemotherapy.
Some patients may receive a hematopoietic cell transplant at this stage. If a patient has a transplant, he or she will be hospitalized for several weeks. It will likely be a year before the patient can return to school.
The goal of the induction phase is to kill leukemia cells in the blood and bone marrow and bring the disease into remission. Since AML patients are vulnerable to infection, supportive therapy with antibiotics is also given. Central nervous system (CNS) sanctuary therapy (also called CNS prophylaxis) may also be given during this time to kill leukemia cells that remain in the brain and spinal cord. Medications are injected into the fluid-filled space between the thin layers of tissue that cover the brain and spinal cord (intrathecal).
The goal of this phase is to kill any remaining leukemia cells that could grow and cause the cancer to relapse. Cancer centers can perform tests that are capable of detecting a single AML cell among 1,000 normal cells. Children who have more than one cell in 1,000 after completing the induction phase are at the greatest risk of relapsing.
This consolidation phase begins after the patient is in remission. It includes 2-4 cycles of chemotherapy and lasts for 4 to 6 months. Such therapy includes some of the drugs used in induction while also introducing non-cross–resistant drugs and commonly high-dose cytarabine.
A hematopoietic cell transplant (also known as a bone marrow transplant or stem cell transplant) may be recommended for children who are at high risk for relapse or whose AML is resistant to treatment. Doctors sometimes look at how well induction chemotherapy worked to decide whether a bone marrow transplant is needed.
AML patients may receive an allogeneic transplant.
In an allogeneic bone marrow transplant, children receive blood cell-producing cells from a healthy donor. Patients must have a suitable donor to be eligible for a transplant. Before receiving the donor cells, the patient’s existing blood cells in the bone marrow are destroyed by chemotherapy and sometimes radiation. The patient receives the healthy donor blood and marrow cells through an infusion. If successful, these new donor cells will grow into and replace the patient’s blood and marrow cells. As a result, the patient’s bone marrow should start to produce healthy blood cells.
The five-year survival rates for childhood AML is about 70 percent.
About 90 percent of children with AML have no cancer cells in their blood after initial treatment. About 30 percent of children with AML relapse or have disease that is resistant to treatment (refractory).
A late effect is a health problem that occurs months or years after a disease is diagnosed or after treatment has ended. Late effects may be caused by cancer or cancer treatment. They may include physical, mental, and social problems and second cancers.
Late effects may include:
Current research focuses on developing more effective treatments for children whose cancer doesn’t respond to the original therapy, developing more therapies that target the cancer cells without harming surrounding healthy cells, and designing effective therapies with fewer side effects.
Reviewed: June 2018