Chronic Myeloid Leukemia (CML): Phases

March 21, 2017

Chronic Myeloid Leukemia (CML): Phases 

What does phase of CML mean?

Most types of cancer are noted 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 is in your bone marrow and blood, the leukemia cells are always traveling around the body. 

Instead of stages, CML is described in phases. The phases note how many immature white blood cells (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 the leukemia. 

The phases of CML

There are 3 phases of CML, including: 

  • Chronic phase. During this phase, there are fewer than 10% immature white blood cells (blasts) in your blood or bone marrow. Symptoms are mild symptoms and get better with standard treatments. Most people diagnosed with CML are in this phase.

  • Accelerated phase. During this phase, there are more than 10% but fewer than 20% blasts. Or there is more than 20% of another type of white blood cell called basophils. Or there is a very abnormal platelet count. You may have symptoms such as a fever, low appetite, and weight loss. Symptoms and blood counts may not respond as well to treatment. The leukemia cells may have other changes in the chromosomes, in addition to the Philadelphia chromosome.

  • Blast phase (blast crisis). During this phase, there are more than 20% of the blasts in your blood or bone marrow. These blast cells often spread to other areas of your body outside the bone marrow.  You may have symptoms such as tiredness, fever, loss of appetite, and an enlarged spleen. This phase is considered aggressive. This 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.


March 21, 2017

Reviewed By:  

Alteri, Rick, MD,Cunningham, Louise, RN