Chronic Myeloid Leukemia

Overview

Chronic myeloid leukemia (CML) is a cancer that starts in the blood-forming cells of the bone marrow. In CML, the marrow makes too many of a type of white blood cell. It is usually slow-growing, which is why it is called chronic, and it often progresses through phases over time if not treated.

Most cases of CML are linked to a specific genetic change called the Philadelphia chromosome, which produces an abnormal protein that drives the uncontrolled growth of cells. The discovery of this protein led to targeted medications that have transformed treatment, allowing many people with CML to control the disease for many years. CML mainly affects adults and is uncommon in children.

Symptoms

Many people with CML have no symptoms early on, and it is sometimes found on a routine blood test. When symptoms occur, they may include:

• Fatigue and weakness.
• Unintended weight loss.
• Night sweats.
• Fever.
• A feeling of fullness or discomfort under the left ribs from an enlarged spleen.
• Easy bruising or bleeding.
• Frequent infections.
• Bone pain in some cases.

Symptoms tend to be mild in the early (chronic) phase and may become more pronounced if the disease advances.

Causes

CML is caused by a genetic change that develops in a blood-forming cell during a person's lifetime. Specifically:

• Two chromosomes swap pieces, creating the Philadelphia chromosome.
• This produces an abnormal gene that makes a protein driving cells to grow and divide uncontrollably.
• The change is not inherited and is not passed from parent to child; it occurs in the affected cells during life.

The reason the genetic change happens is usually unknown. It is not caused by anything a person did, and in most cases there is no identifiable trigger.

Risk Factors

There are few known risk factors for CML. Those identified include:

• Older age, as risk increases with age.
• Being slightly more common in men.
• Exposure to high doses of radiation, such as from radiation therapy or major radiation accidents, which is uncommon.

Most people who develop CML have no clear risk factor, and the disease is not linked to family history in the usual sense.

Diagnosis

CML is diagnosed through blood and bone marrow testing:

• Complete blood count, which often shows a high white blood cell count.
• Blood smear examined under a microscope.
• Bone marrow tests, in which a small sample is taken to examine the cells.
• Genetic tests that look for the Philadelphia chromosome and the abnormal gene it creates, which confirm the diagnosis and are used to track the disease.

These genetic tests are also used over time to measure how well treatment is working.

Treatment

Treatment has advanced significantly, and many people with CML now manage it as a long-term condition. Options include:

• Targeted therapy with oral medications known as tyrosine kinase inhibitors, which block the abnormal protein and are the main treatment for most people. They can control the disease very effectively, often for many years.
• Regular monitoring with genetic tests to confirm the medication is working and to adjust treatment if needed.
• Stem cell (bone marrow) transplant, which may be considered in selected cases, particularly if other treatments are not effective.
• Other medications or chemotherapy in certain situations.

With consistent treatment and monitoring, the outlook for many people with CML has improved dramatically. Taking medication exactly as prescribed is important to keep the disease under control.

Prevention

There is no known way to prevent CML, because the genetic change that causes it usually occurs for unknown reasons and is not inherited. Avoiding unnecessary exposure to high doses of radiation is the only general precaution, and even that accounts for very few cases. Early detection through a blood test, sometimes done for another reason, can lead to treatment before symptoms become significant.

When to See a Doctor

See a doctor if you have ongoing fatigue, unexplained weight loss, night sweats, fevers, easy bruising or bleeding, frequent infections, or a feeling of fullness or discomfort under the left ribs. A simple blood test can detect abnormalities that prompt further evaluation.

Seek prompt care for severe symptoms such as significant bleeding, very high fever, severe abdominal pain, or feeling extremely unwell, which need urgent assessment. If you are already being treated for CML, report new or worsening symptoms to your care team.

Related Topics

Frequently Asked Questions

References

1. American Cancer Society. Chronic myeloid leukemia.
2. National Cancer Institute (NCI).
3. Mayo Clinic.
4. MedlinePlus, U.S. National Library of Medicine.