Chronic Myeloid Leukemia (CML)

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Chronic Myelogenous Leukemia Facts

About 4,800 people in the United States developed chronic myelogenous leukemia (CML) in 2008.  About 21,000 people in the United States are living with CML (SEER, National Cancer Institute, 2008).  The progress that has been made in treating CML gives patients more hope than ever before.

Leukemia is a type of cancer.  There are four main types of leukemia, and CML is one of the four types. CML starts with a change to a single stem cell. Both children and adults can get CML, but most patients are adults.

Every cell with a nucleus has chromosomes. Patients with CML have the Philadelphia chromosome (Ph chromosome). The Ph chromosome is made as a result of a piece of chromosome 22 breaking off. With CML there is a switch in pieces of chromosome 9 and 22. The break on chromosome 9 involves a gene called ABL, and the break on chromosome 22 involves a gene called BCR. When a piece of chromosome 9 attaches to the end of chromosome 22, the BCR-ABL cancer gene is made. This cancer gene gives the cell instructions to make a protein that leads to CML. 

Phases of CML

CML can have three phases:

  • The chronic phase
  • The accelerated phase
  • The blast crisis phase

Most patients are in the chronic phase of the disease when their CML is found.  During this phase, CML symptoms are less. White blood cells can still fight infection.  Once a patient in the chronic phase is treated, red blood cells and platelets can do their jobs. Most patients can go back to their usual activities.

In the accelerated phase, the patient may develop anemia, the number of white blood cells may go up or down, and the platelets may go down. 

During the blast crisis phase, the number of blast cells increases in the marrow and blood, the number of red blood cells and platelets decreases, the patient may have infections, and the patient may be tired and have shortness of breath, bone pain or bleeding.

Symptoms

CML signs and symptoms usually develop slowly.  Some patients learn about their CML after a routine blood test taken during an annual check-up. Some changes that a person with CML may have are:

  • Tiredness
  • Shortness of breath doing activities
  • Paler skin than usual
  • Enlarged spleen
  • Night sweats
  • Weight loss

Diagnosis

Lab tests are used to make a CML diagnosis and are also to check the patient’s response to treatment. People with CML may need these tests:

  • Blood tests: These are done to look for leukemia cells. In the CML patient, the white blood cell count goes up, often to very high levels. Platelet counts also go up, and hemoglobin levels go down.
  • Bone marrow aspirate or biopsy: This is done to look for leukemia cells and to find out if the person has CML. There are changes in bone marrow cells that cannot be seen in the peripheral blood cells.
  • Cytogenetic analysis: This lab test is done on the peripheral blood as well as the bone marrow. The purpose is to determine if the patient has the Ph chromosome and if the patient has CML.
  • Fluorescence in situ hybridization (FISH): This method measures the percentage of Ph chromosome (CML) cells.
  • Polymerase chain reaction: This is a very sensitive test that can measure cancer cell markers in the blood. It is used to detect remaining blood cancer cells that are below the level of detection of cytogenetic methods like FISH.

Risk Factors

Doctors are working to understand the changes that lead to the development of the Ph chromosome and the BCR-ABL cancer gene.  Some risk factors may be (1) very high levels of radiation (such as in atomic-bomb survivors who were exposed to radiation in WWII) and (2) high-dose radiation therapy used to treat other cancers.  However, most people with CML do not have these risk factors.  There is no link between dental or medical X-rays and risk of CML.  You cannot catch CML from someone else.