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CML Phases and Prognostic Factors

CML has three phases. The phase of your chronic myeloid leukemia (CML) plays a large part in determining the type of treatment you'll receive. Doctors use diagnostic tests to determine the phase of CML. Determining the CML phase is based primarily on the number of immature white blood cells (blasts) in the patient’s blood and bone marrow. 


Chronic Phase. Most patients are diagnosed with CML in the with chronic phase of the disease.

​People with chronic phase CML

  • May or may not have symptoms
  • Have an increased number of white blood cells
  • Usually respond well to standard treatment (i.e., symptoms go away, white blood cell counts return to normal levels, hemoglobin concentration improves and spleen reduces in size)

If untreated, chronic phase CML will eventually progress to accelerated phase CML and/or blast phase CML.

Accelerated Phase. In the accelerated phase, the number of immature blast cells has risen, and sometimes new chromosomal changes, in addition to the Ph chromosome, will occur.

​People with accelerated phase CML may have

  • More than 20 percent basophils (type of white blood cell) in the bloodstream
  • More then 15, but less than 30 percent blasts in the blood and bone marrow
  • Low platelet counts unrelated to therapy
  • Increased spleen size
  • Worsening anemia (caused by low levels of red blood cells)
  • Additional chromosome abnormalities in the CML cells

​In the accelerated phase, the number of CML cells grow faster and cause symptoms such as fatigue, fever, weight loss and an enlarged spleen. If untreated, accelerated phase CML will eventually transform to blast phase CML.

Blast Phase (Also Called "Blast Crisis Phase"). The blast phase appears and behaves like the acute form of myeloid leukemia.

People who have blast phase CML may have

  • Anemia
  • A very high white blood cell count
  • Very high or very low platelet counts
  • Blast cells that have spread outside the blood and/or the bone marrow to other tissues and organs
  • CML cells with new chromosome abnormalities
  • Symptoms such as
    • Fever
    • Fatigue
    • Shortness of breath
    • Abdominal pain
    • Bone pain
    • Enlarged spleen
    • Poor appetite and weight loss
    • Bleeding
    • Infections

Prognostic Factors

Along with the phases of CML, there are other factors that affect treatment decisions and predict a patient’s prognosis (chance for recovery). These are known as “prognostic factors.” The following are prognostic factors for patients with CML at the time of diagnosis:

  • Phase of CML—Patients who have either accelerated or blast phase CML have a less favorable prognosis than those who have chronic phase CML.
  • Age—Patients 60 years of age or older have a less favorable prognosis.
  • Spleen size—A patient with an enlarged spleen has a less favorable prognosis.
  • Platelet count—Patients who have very high or very low platelet counts have a less favorable prognosis.
  • Blasts in the blood—Patients who have a high number of blasts in the blood have a less favorable prognosis.
  • Increased numbers of basophils and eosinophils in the blood—Patients with an increase in these types of white blood cells have a less favorable prognosis.

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