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Chronic Myeloid Leukemia (CML)

Also called chronic myelogenous leukemia, chronic myelocytic leukemia, or chronic granulocytic leukemia

What is chronic myeloid leukemia (CML)?

3D illustration showing defective 9 and 22 chromosomes

The Philadelphia chromosome happens when part of chromosome 9 transfers to chromosome 22.

Chronic myeloid leukemia (CML) is a cancer of the blood and bone marrow.

Leukemia occurs when the bone marrow makes too many cancer cells. These cells are called blasts. As blasts grow and divide rapidly, healthy blood cells cannot do their jobs. The blood does not function correctly. The patient cannot fight infection well.

CML is a chronic leukemia. It develops slowly over time. It may take weeks or months for symptoms to appear. Chronic also means that the leukemia may last a long time. Acute leukemias make children ill quickly.

CML is rare in children. Only 110–120 cases are seen each year in the United States and Canada.

About 90–95% of children with CML have a genetic change called the Philadelphia chromosome. The Philadelphia chromosome is not passed from parent to child. It occurs randomly.

Drugs called tyrosine kinase inhibitors (TKIs) are the first line of treatment. They target tyrosine kinase enzymes, which cause leukemia cells to grow and divide quickly.

Symptoms of CML

CML develops slowly. Children with CML may not have symptoms at first.

Common CML symptoms include:

  • Fatigue
  • Pain or feeling of fullness under the rib cage
  • Weight loss
  • Fever
  • Night sweats
  • Bone and joint pain

Diagnosis of chronic myeloid leukemia

Tests to diagnose CML may include:

  • Physical exam and health history
  • Complete blood count to count the number of white blood cells
  • Bone marrow tests to see if leukemia cells are in the bone marrow 
  • Tests to look at chromosomes and gene changes

During the physical exam, the doctor will check general signs of health. The doctor will: 

  • Look for signs of disease, such as lumps or anything else that seems unusual
  • Feel the patient’s belly for signs of an enlarged spleen or liver
  • Examine the eyes, mouth, skin, and ears

The doctor may conduct a nervous system exam to look at the function of the brain, spine, and nerves. Sometimes they will order diagnostic imaging tests. Diagnostic imaging tests make images of the body’s soft tissues, organs, and bones. 

If tests indicate cancer, doctors will order more tests to find out the type of cancer. 

Phases of CML

CML has 3 phases. The phase depends on the number of leukemia (blast) cells in the blood and bone marrow.

  • Chronic: fewer than 10% blasts
  • Accelerated: 10–19% blasts
  • Blast: 20% or more blasts. During a blast crisis, the patient is tired, has fever, and has an enlarged liver and spleen.

Treatment for chronic myeloid leukemia

Treatment depends on the phase of cancer.

First-line treatment for CML is usually the drug imatinib (Gleevec®). This drug is a type of targeted therapy known as tyrosine kinase inhibitor (TKI). Tyrosine kinase is a property of certain enzymes made by the body. The tyrosine kinase activity can become too high in cancer, causing cancer cells to grow. Imatinib blocks the tyrosine kinase activity and helps stop the growth of cancer cells.

Other TKI drugs called dasatinib, nilotinib, and ponatinib are sometimes used if patients cannot tolerate imatinib. These drugs are sometimes called 2nd generation TKIs.

During treatment, doctors closely watch how patients respond to therapy. This is called monitoring. Monitoring may include a health history, physical exam, complete blood count, and molecular testing.

Molecular testing can measure the number of leukemia cells in blood. It can find 1 leukemia cell among 10,000–100,000 normal cells. Molecular tests occur every 3–6 months after the start of therapy.

Testing can also show changes in CML cells. After taking a TKI drug, CML cells may change. The change may mean the medicine will not work as well. Doctors use this information to guide treatment.

Children may face side effects not seen in adults, such as growth problems. This is because children are growing during treatment with TKI drugs. Talk to your child’s care team about possible side effects.

Stem cell transplant

stem cell transplant (also known as bone marrow transplant or hematopoietic cell transplant) is another treatment option for CML.

A transplant can cure CML. But the patient must have a suitable cell donor.

A transplant can have serious side effects.

Darshana Magan

Childhod cancer survivor story

"I bungee jumped in New Zealand. I skydived in Montauk. I rock climbed and rappelled next to a waterfall. If I can beat cancer, there's nothing that I can't do." —Darshana Magan

Darshana Magan was diagnosed with an advanced stage of chronic myeloid leukemia when she was 11. Learn how she dealt with her fear of relapse and now advocates for her health as an adult childhood cancer survivor.

Read her story

Prognosis of CML

When discussing prognosis, doctors often talk about the 5-year survival rate. This rate is the percentage of patients who live at least 5 years after diagnosis.

For chronic leukemias, 5-year survival rates are less helpful. Children may live for a long time with their leukemia without being cured. Five-year survival rates for pediatric CML are 90% in the United States.

Support for CML patients

Patients who take TKI drugs

Patients may need to take TKI drugs to treat their CML for the rest of their lives. The long-term side effects of these drugs, such as effects on puberty and fertility, are not known. Researchers trying to find out if it is possible to stop taking TKI drugs or reduce their dosage.

Patients who had stem cell transplants

Stem cell transplants can also have long-term side effects. These may include problems with growth, puberty, fertility, and organ function. Talk to your care team for more details.

It is important to have regular follow-up appointments. Patients should also have good health habits. These include eating healthy foods, doing regular physical activities, and getting enough sleep. Talk to your care team for more information. 

Questions to ask your care team

  • What are my child’s treatment options? 
  • What are the possible side effects of treatment? 
  • What can be done to manage side effects? 
  • Will my child need to be in the hospital for treatment? 
  • Where is the treatment available? Is it close to home or will we have to travel? 
  • Will the treatment affect my child’s ability to have children in the future? What are fertility preservation options? 

Key points about CML

  • Chronic myeloid leukemia (CML) is a blood and bone marrow cancer. CML is rare in children.
  • Most children with CML have a genetic change called the Philadelphia chromosome.
  • Drugs called tyrosine kinase inhibitors (TKIs) are the first line of treatment for CML. They target an enzyme that causes leukemia to cells to grow and divide quickly.
  • Doctors closely watch how patients respond to therapy.
  • Talk to your child’s care team about possible side effects.

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Reviewed: August 2023

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