Chronic Myelogenous Leukemia (CML)

What Is Chronic Myelogenous Leukemia?

Chronic myelogenous (mye-eh-LAH-jeh-nis) leukemia is a type of leukemia that develops in the bone marrow, the soft spongy area inside the bones.

It starts in early myeloid (MYE-eh-loyd) cells, which are blood cells that usually become white blood cells. These myeloid cells do not mature normally into white blood cells. Instead, they collect in the bone marrow and blood in large numbers.

Chronic myelogenous leukemia is also known as chronic myeloid leukemia.

What Causes Chronic Myelogenous Leukemia?

A chromosomal problem causes chronic myelogenous leukemia. Chromosomes contain pieces of DNA called genes. There are 23 pairs of chromosomes.

CML happens when a piece of a chromosome breaks off and attaches to a part of another chromosome. The combination of the two chromosomes forms an abnormal gene known as BCR-ABL. This gene then guides the body to make too many abnormal white blood cells.

Who Gets Chronic Myelogenous Leukemia?

Chronic myelogenous leukemia is very rare in children. Each year, only about 150 children in the United States are diagnosed with CML.

Although researchers know which genes are involved in the development of CML, they do not yet know why some people get it and others do not.

What Are the Signs & Symptoms of Chronic Myelogenous Leukemia?

Chronic myelogenous leukemia tends to progress slowly. So at first a child may have few or no symptoms. In fact, symptoms can take months or even years to develop.

The symptoms of all types of leukemia are generally the same and include:

• getting a lot of infections (such as or tonsillitis) because the white blood cells don't fight infection as usual
• tiredness and weakness due to infections
• swollen lymph nodes from cancer cells collecting in them
• fever due to infections
• easy bruising or bleeding because the bone marrow doesn't make enough platelets (cells that help blood clotting)
• bone and joint pain because the bone marrow is full of abnormal cells
• belly pain and swelling caused by abnormal blood cells building up in organs like the kidneys, liver, and spleen

How Is Chronic Myelogenous Leukemia Diagnosed?

Because symptoms might not begin for quite a while with chronic myelogenous leukemia, doctors might find it when a child has a routine blood test for other reasons. 

When doctors suspect CML, they will order more tests, such as:

• Blood tests. Tests such as a complete blood count, liver and kidney function panels, and blood chemistries can give important information about the number of normal blood cells and how well the organs are working. The shapes and sizes of the blood cells are checked with a microscope.
• Imaging studies. These may include an X-ray, CT scan, MRI, or ultrasound. These can see whether there's a mass of leukemia cells in the chest that could affect breathing or blood circulation. They also can rule out other possible causes of a child's symptoms.
• Bone marrow aspiration and biopsy. The doctor puts a needle into a large bone, usually the hip, and removes a small amount of bone marrow. Then the lab does these tests on the bone marrow sample:
  • Flow cytometry tests. Doctors look at the cancer cells and figure out the type of leukemia. This is important because treatment differs depending on the type.
  • Genetic tests. By looking at the blood or bone marrow, doctors check for changes in the genes. The changes can help doctors figure out the best treatment.
  • Tissue typing or HLA (human leukocyte antigen) typing. If a child needs a stem cell transplant (bone marrow transplant), this test helps doctors find a suitable stem cell donor. It works by comparing the proteins on the surface of a child's blood cells with the proteins on a potential donor's cells. The more HLA markers a child and donor share, the greater the chances that a transplant will be successful.

How Is Chronic Myelogenous Leukemia Treated?

Treatment of CML depends on things like:

• the stage of the leukemia (whether it's in the early or later stages)
• the number of cancerous cells in the body
• how well the liver, kidneys, and spleen are working

This information, in addition to a child's age and overall health, helps doctors develop treatment plans that may include:

• Targeted therapy. This treatment uses medicines to find and attack the cancer cells without hurting the normal cells. These medicines, called tyrosine kinase inhibitors (TKI), target the cancer cells in CML and are usually used as the first treatment for patients with early CML.
• Chemotherapy. This is the use of special medicines to kill cancer cells. Some are used in combination to attack the cells in different ways.
• Rarely, stem cell transplant (bone marrow transplant). This involves destroying cancer cells and normal bone marrow and immune system cells with high-dose chemotherapy and then putting healthy donor stem cells into the body. The new stem cells can rebuild a healthy blood supply and immune system.

The goal is remission, which is when there is no evidence of cancer cells in the body. Then, doctors use tyrosine kinase inhibitors to keep a child in remission and to keep killing cancer cells. The cancer team regularly checks how the chemotherapy is working by doing blood tests and measuring how many abnormal genes remain in the blood.

Looking Ahead

Having a child being treated for cancer can feel overwhelming for any family. But you're not alone. To find support, talk to your child's doctor or a hospital social worker. Many resources are available to help you get through this difficult time.