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Chronic Myeloid Leukemia (CML): Phases 

What does phase of CML mean?

Most types of cancer are grouped in stages. Stages tell the size of the tumor and how far the cancer has spread. But chronic myeloid leukemia (CML) is different. It rarely causes tumors. And because it's in your bone marrow and blood, the leukemia cells are always moving around the body. 

Instead of stages, CML is described in phases. The phases note how many immature white blood cells (called blasts) are in the blood or bone marrow. The phase of CML is one of the most important things to know when deciding how to treat this type of leukemia. 

The phases of CML

There are 3 phases of CML: 

  • Chronic phase. During this phase, you have fewer than 10% immature white blood cells, called blasts, in your blood or bone marrow. If there are symptoms, they're mild and get better with treatment. Most people diagnosed with CML are in this phase. It can last many years.

  • Accelerated phase. During this phase, you have 1 or more of these:

    • 15% or more, but fewer than 30% blasts

    • 20% or more of a type of white blood cell called basophils

    • A very low platelet count (these are blood cells that prevent bleeding by helping the blood to clot)

    • The number of blast cells plus the number of promyelocytes (an immature myeloid cell) make up 30% or more of your blood

    • New gene changes in the leukemia cells that have the Philadelphia chromosome

  • You may have symptoms such as a fever, low appetite, enlarged spleen, and weight loss. Symptoms and blood counts may not respond as well to treatment.

  • Blast phase (blast crisis). During this phase, you have 30% or more blasts in your blood, bone marrow, or both. These blast cells often spread outside the bone marrow. Blood counts are not normal. You may have symptoms such as severe tiredness (fatigue), fever, loss of appetite, bleeding, shortness of breath, and an enlarged spleen. This phase means the cancer is growing quickly.

Talking with your healthcare provider 

Once the phase of your CML is known, your healthcare provider will talk with you about what it means for your treatment. Make sure to ask any questions or talk about your concerns.

Online Medical Reviewer: Kimberly Stump-Sutliff RN MSN AOCNS
Online Medical Reviewer: Louise Cunningham RN BSN
Online Medical Reviewer: Todd Gersten MD
Date Last Reviewed: 2/1/2021
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