Chronic Myeloid Leukemia (CML)

In chronic myeloid leukemia, a type of leukemia, patients have an abnormal chromosome in their blood cells called the Philadelphia chromosome, which was discovered at Penn. This slow-growing blood cancer takes longer to develop and can progress into acute leukemia, which needs immediate medical attention. The leukemia specialists at Penn Medicine offer personalized, cutting-edge treatments for CML and other blood cancers.

What is Chronic Myeloid Leukemia (CML)?

Chronic myeloid leukemia (CML) is a slow-developing cancer of the bone marrow in which immature cells called “blasts” overtake the healthy bone marrow. Patients with CML have an abnormal chromosome in their blood cells called the Philadelphia chromosome. No one is born with the Philadelphia chromosome; rather it is a result of a genetic accident that happens in a blood-forming stem cell in the bone marrow. It is actually a combination of 2 chromosomes (chromosomes 9 and 22) that become abnormally fused. This fusion results in the creation of a new gene called BCR-ABL.

Chronic myeloid leukemia is classified as a myeloproliferative neoplasm. These are slow growing types of leukemia which result in overproduction of white blood cells by the bone marrow, causing high blood counts.

Chronic myeloid leukemia (CML) may also be referred to as chronic myelogenous leukemia, chronic myelocytic leukemia or chronic granulocytic leukemia.

Acute vs. Chronic Myeloid Leukemia

Unlike acute myeloid leukemia (AML), CML takes longer to develop. Most people can live with CML for many years. Rarely CML can also turn into acute leukemia, which needs immediate medical attention. It is also important to know that some patients with acute leukemia (especially acute lymphocytic leukemia) have the Philadelphia chromosome, but do not have CML. Treatment is different, though some strategies overlap for CML and ALL with the Philadelphia chromosome.

CML Symptoms and Signs

Signs and symptoms of CML may look like other signs and symptoms of diseases or conditions.

If you have any, some, or all, of these symptoms*, please speak with your physician:

  • Pale skin
  • Shortness of breath
  • Tiredness, lethargy
  • Night sweats
  • Unexplained weight loss / loss of appetite
  • Enlarged spleen or liver (upon physician examination)

*From the Leukemia and Lymphoma Society

Types of Chronic Myeloid Leukemia

Chronic Myeloid Leukemia (CML) has three phases:

  • Chronic phase
  • Accelerated phase
  • Blast phase

Most patients with CML are diagnosed in the chronic phase of disease, when they have only a small number of immature cells (blasts) in the blood or bone marrow. Often they only find out they have the disease because blood counts were checked and found to be abnormal. In accelerated and blast phase disease, the number of immature cells increase, and patients typically experience more symptoms.

People with CML have either the Philadelphia chromosome, or the gene made by the Philadelphia chromosome called Bcr-Abl. When you are diagnosed, your physicians will request testing to find out if you have the Philadelphia chromosome or Bcr-Abl. New, targeted treatments have been developed to treat these chromosomal abnormalities.

How Is CML Diagnosed?

Many people do not have symptoms of chronic myeloid leukemia (CML) when they are diagnosed. They may be diagnosed during a routine checkup, or if their family doctor prescribes blood tests for an unrelated issue.

If your doctor suspects CML, further leukemia diagnosis tests will determine if you have the Philadelphia chromosome, or the Bcr-Abl oncogene. The phase of your CML will also be identified, usually by a bone marrow biopsy. Knowing all of this information will allow us to use different targeted therapies specific to your type of cancer.

Staging Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is not staged like other solid tumor cancers. Instead, CML is broken down into three phases. The number of blasts present in the blood stream identifies each phase.

  • The Chronic Phase: In the Chronic Phase, people with CML may have little or no symptoms at all. A blood test may detect the CML. In this phase, the CML may be controlled with drugs. If you become resistant to drugs, your disease may progress to the next phase, the Accelerated Phase.
  • The Accelerated Phase: In the Accelerated Phase of CML, you may begin experiencing symptoms associated with an enlarged spleen, low red blood cell count, or an increase or decrease in white blood cells.
  • The Blast Phase: The Blast Phase of CML is diagnosed when you have an increase of blast cells in your bone marrow and blood. In this phase, you are at higher risk for other complications of CML such as shortness of breath, infection and bleeding. Once CML gets to the Blast Phase, it can accelerate into acute lymphocytic leukemia (ALL) or acute myeloid leukemia (AML), and requires immediate medical attention.

CML Treatment Process and Options

The diagnosed phase of your chronic myeloid leukemia (CML) and presence of the Philadelphia chromosome, or Bcr-Abl oncogene, will determine your treatment plan. Penn Medicine's Abramson Cancer Center's hematologists and medical oncologists are part of large multidisciplinary leukemia treatment teams whose approach to cancer and blood disorders is to treat the entire individual — not just the disease. Some of the procedures used to treat your CML include the following:

Treatment for Chronic Myeloid Leukemia (CML) – Chronic Phase

In the Chronic phase, CML may be controlled with drugs. If you become resistant to drugs, your disease may progress to the next phase, the Accelerated Phase. Through research and clinical trials, people with CML can now live longer, symptom-free lives.

Speak with your hematologist-oncologist about your options for treatment, and current clinical trials available for people with CML.

Treatment for Chronic Myeloid Leukemia (CML) – Accelerated Phase

In the Accelerated Phase of CML, you may be given drugs to help you get into remission, with no evidence of leukemia, or back into the chronic phase. Also, if you have very high blood counts, your doctor may recommend removal of white blood cells through a process called leukapheresis.

Treatment for Chronic Myeloid Leukemia (CML) – Blast Phase

The Blast Phase of CML is diagnosed when you have an increase of blast cells in your bone marrow and blood. In this phase, you are at higher risk for other complications of CML such as shortness of breath, infection and bleeding. Treatment for this phase of CML includes those listed above. Your doctor may also speak with you about a stem cell transplant.

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