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Chronic Myeloid Leukemia

Chronic myeloid leukemia is a type of leukemia that starts in the myeloid cells in the bone marrow. These cells normally help the body fight infection but in this type of cancer are instead more likely to cause infection by creating an imbalance to the healthy blood cells.

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About This Condition

Understanding Chronic Myeloid Leukemia

What is chronic myeloid leukemia (CML)?

Chronic myeloid leukemia (CML) is a type of leukemia that starts in myeloid cells in the bone marrow.  It’s also known as chronic myelogenous leukemia. It starts in cells that normally help the body fight infections.

There is a change in a chromosome in the cells of almost all patients with CML. The change is called the Philadelphia chromosome. It creates an abnormal gene called BCR-ABL. This causes the leukemia cells to grow out of control.

As the leukemia cells grow, they can crowd out the normal cells in the bone marrow. This can lead to not enough different types of blood cells. People with CML have too many white blood cells in their blood.

CML is a type of chronic leukemia. This means it tends to grow slowly. CML does not always cause symptoms right away. Some people with CML have no symptoms when CML is diagnosed.

What are the symptoms of chronic myeloid leukemia (CML)?

Some people don’t have any symptoms before being diagnosed with CML. The cancer is often found when a person has blood tests done for another reason and the tests show too many white blood cells. If CML does cause symptoms, they can include:  

  • Feeling tired (fatigue).
  • Feeling weak.
  • Fevers.
  • Chills or night sweats.
  • Frequent infections.
  • Pain or a sense of fullness in the upper abdomen, from an enlarged spleen.
  • Feeling full after eating only a small amount.
  • Weight loss.
  • Bleeding or bruising easily.
  • Bone or joint pain.
  • Itchy skin.

Many of these symptoms can be caused by other health problems. In fact, most of them are more likely to be caused by something else. However, it is important to see your healthcare provider if you have these symptoms. Only a healthcare provider can tell if you have CML, another type of cancer, or some medical problem that needs to be treated.

How is chronic myeloid leukemia (CML) diagnosed?

If your healthcare provider thinks you might have CML, you will need certain exams and tests to be sure. Your healthcare provider will ask you about your health history, your symptoms, risk factors, and family history of disease. Your healthcare provider will also give you a physical exam.

What tests might I need?

You may have one or more of the following tests:  

  • Blood tests. CML is often found with blood tests before you have symptoms. Blood is taken from the arm or hand with a needle. Tests can look at the numbers of different types of blood cells. People with CML often have too many white blood cells.

  • Bone marrow aspiration and biopsy. This procedure is done by taking small amounts of bone marrow fluid (aspiration), solid bone marrow tissue (core biopsy), or both. Bone marrow samples are usually taken from the back of the hip (pelvic) bone. For the bone marrow aspiration, the area over the hip is numbed. A thin, hollow needle is inserted into the pelvic bone. A syringe is used to pull out a small amount of liquid bone marrow. You may have some brief pain when the marrow is removed. A bone marrow biopsy is usually done just after the aspiration. A slightly bigger needle is used to take out a small core of bone and marrow. The biopsy may also cause some brief pain. The fluid and bone marrow are looked at for the number, size, and maturity of blood cells and abnormal cells. Other tests can also be done on these cells.

How is blood or bone marrow tested?

Nearly all CML has a genetic change called the Philadelphia chromosome, an abnormal gene called BCR-ABL, or both. People with CML also have too many white blood cells. Tests are used to look for these changes. The tests done on blood or bone marrow samples may include:                                                                                                                                                            

  • Cytogenetics. For these tests, cells are grown in a lab for a week or more. The chromosomes inside the cells are then stained with special dyes and viewed with a microscope. Major problems in the chromosomes can often be seen. But smaller changes may not be visible. These tests usually take a few weeks. This is because the cells need time to be grown in the lab.

  • Fluorescence in situ hybridization (FISH). This test is another way to look for changes in chromosomes. The cells in the sample are stained with fluorescent dyes that will only attach to certain parts of chromosomes. The cells are then viewed with a microscope using a special light. This test can find some chromosome changes that can't be seen with standard cytogenetic testing. It's also a quicker test. 

  • Polymerase chain reaction (PCR). This is a very sensitive test that can detect very low levels of leukemia cells in a test sample. It works by increasing the amount of genetic material in a sample so that it can be detected. This test can find small levels of chromosome changes such as the BCR-ABL gene that other tests may not find.

Getting your test results

When your healthcare provider has the results of your tests, he or she will contact you with the results. Your provider will talk with you about other tests you may need if CML is found. Make sure you understand the results and what follow-up you need.

What is a phase of CML?

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's 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 this type of leukemia.

The phases of CML

There are three phases of CML: 

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

  • Accelerated phase. During this phase, you have more than 10% but fewer than 20% blasts. Or you have more than 20% of another type of white blood cell called basophils. Or you have a very abnormal platelet count. 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. The leukemia cells may have abnormal changes in their chromosomes.

Blast phase (blast crisis). During this phase, you have more than 20% of the blasts in your blood or bone marrow. These blast cells often spread outside the bone marrow. Blood counts are not normal. You may have symptoms such as tiredness, fever, loss of appetite, bleeding, shortness of breath, 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.

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