There are three phases, or stages, of chronic myeloid leukemia (CML) — chronic, accelerated, and blast. CML blast crisis is also referred to as the blast phase, acute phase, or blast crisis phase. The phase of CML is based on how many blasts (immature white blood cells) are in the blood or bone marrow. People with chronic phase CML have fewer blast cells than people with accelerated and blast phase CML. Chronic means that leukemia usually gets worse slowly. If you have been diagnosed with CML, ask your doctor to explain your phase clearly, in a way that you can understand.

What Is CML Blast Crisis?

CML blast crisis is usually the last stage of CML disease progression. Bone marrow and blood samples from people with CML blast crisis will have 20 percent or more blasts present. Blast cells may also be found in other organs or tissues around the body outside of the bone marrow. People with CML blast crisis may have very similar symptoms to those of a person with acute myeloid leukemia.

People living with CML may progress to the blast stage if they do not receive treatment in earlier stages or if their cancer becomes resistant to therapy.

What Are the Symptoms of CML Blast Crisis?

CML symptoms are caused by leukemia cells replacing normal cells. The body cannot function properly without these cells.

The symptoms of the blast phase include:

• High fever
• Tiredness
• Shortness of breath
• Stomach pain
• Bone pain
• Little or no appetite and weight loss
• Unexplained bleeding
• Infections

People with CML blast crisis may have abnormal laboratory test results, including:

• Anemia (low red blood cells)
• Very high white blood cell count
• Either high or low platelet count

How Is CML Blast Crisis Diagnosed?

If you begin to have symptoms of blast crisis, your doctor will order tests to check your blood and bone marrow for signs of blast crisis.

Only 1 percent to 2 percent of people are diagnosed with CML for the first time in the blast phase.

Blood Tests

For blood tests, blood is usually taken from a vein in your arm. A complete blood count (CBC) will tell your doctor how many of each type of cell is present in your blood. They will also look at your blood under a microscope to examine what the cells look like. This is called a peripheral blood smear.

Results of a CBC for people with leukemia look different from CBC for someone without leukemia, including:

• Increased number of white blood cells (WBCs)
• Low red blood cells (RBCs)
• Increased number of immature WBCs (blasts)
• A low or high number of platelets

Your doctor will also use blood tests to find out if you have any problems in your kidneys or liver.

Bone Marrow Samples

Because leukemia starts in the bone marrow, your doctor needs to test samples of your bone marrow. Your doctor will examine the sample to see if it has more blood-forming cells than expected.

Genetic Tests

Your doctor may order tests to see if there have been any changes to the cancer cells. Blast crisis can be caused by genetic changes.

If you have not already been diagnosed with CML, your doctor will look for abnormalities in your DNA and its structure (called chromosomal abnormalities). They will specifically be looking for what is known as the Philadelphia chromosome. This chromosome has an abnormal gene (mutation) called BCR-ABL1, which makes an abnormal protein called tyrosine kinase. This tyrosine kinase causes CML cells to grow out of control.

Your doctor may also check for gene mutations that can cause certain treatments to be less effective.

What Are the Treatment Options for CML Blast Crisis?

The goal of treatment for blast crisis is to return to the chronic phase. Treatment options for CML blast crisis depend on which treatments you have been on in the past. Treatment for the blast phase of CML may be similar to other types of leukemia, like acute myeloid leukemia or acute lymphocytic leukemia. This is because the blast phase acts very similarly to the acute phases of leukemia.

Targeted Therapy

Drugs that target a protein unique to CML cells are typically the first treatments tried. These medications are called tyrosine kinase inhibitors (TKIs). TKIs usually work best for people in the chronic phase of CML but can also help people in more advanced phases.

Imatinib mesylate (Gleevec) is first-line therapy for people who have not been treated for CML before. However, doses must be higher, and it might not work for as long during a blast crisis as it does when it’s used earlier in the disease.

If you are already taking a TKI or if your leukemia has become resistant to imatinib, your doctor may increase your dose, try a different drug, or add chemotherapy to your treatment. Other TKIs that your doctor may recommend include:

• Dasatinib (Sprycel)
• Nilotinib (Tasigna)
• Bosutinib (Bosulif)
• Ponatinib (Iclusig)
• Asciminib (Scemblix)

Chemotherapy

Chemotherapy is the use of drugs to treat cancer by killing rapidly growing cancer cells.

Chemotherapy drugs that may be used to treat blast phase CML include:

• Hydroxyurea
• Cytarabine (ara-C)
• Busulfan (sold as Myleran and Busulfex)
• Cyclophosphamide (Cytoxan)
• Vincristine sulfate
• Daunorubicin (Cerubidine)
• Adriamycin

Stem Cell Transplant

Stem cell transplants, sometimes referred to as bone marrow transplants, may be offered to people in the blast phase of CML, especially if they can be brought back to the chronic phase of CML.

Supportive Treatment

You may receive treatments to help you deal with the symptoms of CML or the side effects of medications. Because most people with blast phase CML can’t be cured, your treatments might be focused on improving your quality of life. This is known as palliative care.

Radiation

Radiation therapy destroys cancer cells using high-energy rays. This is not usually part of CML treatment but can be used to relieve pain caused by bone damage or an enlarged spleen.

Surgery

If leukemia spreads to the spleen, it may become large enough to press on other organs and cause pain and discomfort. When this happens, your doctor may recommend removing your spleen in a procedure called a splenectomy.

Investigational Approaches

You may be asked to join a clinical trial for CML. Clinical trials are used to study the effects of new drugs or procedures on people. There are risks and benefits to joining a clinical trial. Talk to your health care team to decide if this option is right for you.

Outlook for CML Blast Crisis

With treatment advances in targeted therapy like TKIs, most people with CML can expect an average life expectancy. However, about 1 percent to 5 percent of patients will progress to the accelerated phase or blast phase from the chronic phase every year, according to findings published in the British Journal of Haematology. Studies show that most people who progress to the blast phase have an overall survival rate of less than 12 months, according to the authors.

Prognostic factors (predictors) for progressing to the blast phase include:

• Not receiving TKI therapy
• Low platelet count
• Age over 60 years
• Several genetic mutations

Talk With Others Who Understand

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