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Chronic myeloid leukemia (CML) is a type of cancer that starts in the blood-forming cells of the bone marrow and invades the blood. CML is also called “chronic myelogenous leukemia,” “chronic granulocytic leukemia, “and “chronic myelocytic leukemia.” CML is one of four main types of leukemia. CML in children is very rare.
Since the introduction of tyrosine kinase inhibitor (TKI) therapy in 2001, CML has been transformed from a life-threatening disease to a manageable chronic condition for most patients. Most CML patients are treated with daily oral drug therapy. People with CML are living longer and experiencing fewer treatment side effects. Patients who meet specific criteria may even have the option of discontinuing treatment once their disease is in remission.
Find facts and statistics about CML and other blood cancers.
The information on this page covers how CML is diagnosed in adults. Visit CML in children and young adults to learn about signs and symptoms, diagnosis, and treatment information for children with CML.
What should I do if I am diagnosed with CML?
- Talk with your doctor about your diagnostic tests and what the results mean
- Make sure your doctor continually monitors your response to medication, which is essential to bringing your CML under control
- Choose a doctor who specializes in treating CML, known as a hematologist-oncologist. Your local cancer specialist can also work with a leukemia specialist. Learn how to choose a blood cancer specialist or treatment center.
- Talk to your doctor about all of your treatment options, goals of treatment, and the results you can expect from treatment
- Obtain and keep records of your test results and the treatment you receive as this information is useful for long-term follow-up of your condition. Find out how.
Learn more about communicating with your blood care specialist or find a list of suggested questions to ask your healthcare providers.
How does CML develop?
Most blood cells are made in the bone marrow, the soft spongy tissue in the center of bones. They begin as stem cells and develop into healthy red blood cells, white blood cells, and platelets. Once developed, they leave the bone marrow and enter the bloodstream.
CML starts with a mutation (change) to a single stem cell in the bone marrow. This mutated stem cell becomes a leukemia cell and beings to multiply into many CML cells.
Without treatment, the number of red blood cells becomes lower than normal; the number of white blood cells becomes higher than normal and continues to grow.
View a 3D model of CML’s impact on the body. Click or tap the "Interact in 3D" button to begin.
The Philadelphia chromosome
In CML cells, a change takes place on chromosome 22. The changed chromosome 22 is known as the Philadelphia chromosome, or the Ph chromosome. The Ph chromosome is created when a piece of chromosome 22 breaks off and attaches to the end of chromosome 9. A piece of chromosome 9 also breaks off and attaches to the end of chromosome 22.
BCR::ABL1 cancer gene
The break on chromosome 22 involves a gene called BCR. The break on chromosome 9 involves a gene called ABL1. The BCR and ABL1 genes combine to make the CML-causing gene, called BCR::ABL1. This gene makes an abnormal protein that signals to the body to make too many granulocytes (white blood cells). The white blood cells that have the BCR::ABL1 oncogene are called “leukemia cells” or “CML cells.”
Leukemia cells are abnormal. They do not become healthy white blood cells, and they do not die when they should. Over time, the leukemia cells build up in the bone marrow and crowd out healthy blood cells.
How the BCR::ABL1 cancer-causing gene is created
This graphic illustrates how the BCR and ABL1 genes combine to make the CML-causing gene, called BCR::ABL1.
What are risk factors for CML?
For most people who have chronic myeloid leukemia (CML), there are no obvious reasons why they develop the disease. No one is born with CML. It happens when there is an injury to the DNA of a single bone marrow cell.
Risk factors for CML are:
- Sex: CML is slightly more common in males than females
- Age: the risk of getting CML increases with age
- Radiation exposure: in a small number of patients, CML is caused by exposure to very high doses of radiation (such as being a survivor of an atomic bomb blast or a nuclear reactor accident)
- A slight increase in risk also occurs in some individuals treated with high-dose radiation therapy for other cancers, such as lymphoma. Most people treated for cancer with radiation do not develop CML, and most people who have CML have not been exposed to high doses of radiation.
- Exposures to diagnostic dental or medical X-rays have not generally been associated with an increased risk of CML. CML has been reported in individuals undergoing excessive diagnostic X-rays or computed tomography (CT) scans, so every X-ray and CT scan should be well justified to minimize the risk of CML and other types of leukemia.
Source: Chronic Myeloid Leukemia: In Detail. Reviewed by Linday A.M. Rein, M.D.
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