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What is chronic myeloid leukemia (CML)?
Chronic myeloid leukemia (CML) is a cancer of the blood and bone marrow. All blood cells are made by stem cells in the bone marrow, which is the spongy tissue inside your bones.
There are 3 types of blood cells:
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Red cells, which carry oxygen to all the tissues in the body |
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White cells, which fight infection |
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Platelets, which allow the blood to clot to help stop bleeding when a
blood vessel is damaged |
In CML, the stem cells in the bone marrow make too many white blood cells, some of which never mature. These immature white blood cells collect in the bone marrow and blood. Eventually, the extra white blood cells crowd out the healthy red cells and platelets and interfere with the functioning of other organs. This causes the symptoms of CML.
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What causes chronic myeloid leukemia (CML)?
Like most cancers, CML is caused by unhealthy changes in cells. These changes are called mutations. In CML, the mutation occurs in the DNA of the stem cells. DNA is the part of the cell that controls what the cell looks like and what its job in the body will be. For instance, DNA in a bone marrow stem cell tells it to make blood cells. A mutation changes the DNA and how the cell acts.
Genes, which make up chromosomes (KRO-muh-somes), contain DNA. In healthy cells, minor mutations can sometimes occur without causing any problems. But sometimes, the wrong mutation occurs at the wrong time. When the DNA in the chromosome of a bone marrow stem cell is broken and then rejoined in a certain way, it forms a new chromosome. In the case of CML, this chromosome is called a Philadelphia chromosome. Almost all patients with CML have this new chromosome. It causes the stem cells to make too many white blood cells.
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What are the phases of chronic myeloid leukemia (CML)?
CML has 3 phases:
1-Chronic phase
In this phase, healthy white blood cells and platelets are still working well, even though too many white blood cells are being produced. Some immature cells escape into the bloodstream, but this does not happen enough to cause problems. That's why people with CML have few or no symptoms during this early stage. The chronic phase may last for a few months to a few years, but will progress to the next phase in time.
2-Accelerated phase
As the disease gets worse, the number of white blood cells and immature cells increases in the bloodstream. Symptoms begin to appear and worsen, and the disease progresses. This phase is harder to manage and may become more difficult as symptoms get worse.
3-Blast phase
During this phase, more than 30% of the cells in the bloodstream and the bone marrow are immature cells, called blasts. The disease becomes severe and may become life threatening. Sometimes the blast cells form tumours in the bone or lymph nodes. Lymph nodes are the small structures in the body that produce and store infection-fighting cells.
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Who is more likely to get chronic myeloid leukemia (CML)?
CML affects about 480 people in the Canada each year. It occurs most often in adults. More men than women get CML.
The risk for the disease increases with age. About 1 in every 100,000 people who are age 50 or older will get CML. The risk increases to 1 in every 10,000 for people who are age 80 or older.
A very small number of children may also get CML. Only about 2% of all patients who develop CML are younger than age 20.
The broken bones and fractures that result from untreated osteoporosis can also lead to disability and loss of independence.
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What are the signs or symptoms of chronic myeloid leukemia (CML)?
The symptoms of CML develop slowly. Sometimes people find out that they have CML before they have symptoms. Doctors often find the disease during a regular medical check-up or through a blood test for something else.
Some common symptoms of CML include:
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Feeling generally unwell |
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Tiring easily |
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Having a pale complexion |
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Feeling short of breath while being active |
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Not feeling as hungry as usual |
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Feeling discomfort on the left side of the belly |
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Sweating a lot, especially at night |
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Losing weight without trying |
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Being very uncomfortable in warm temperatures |
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Bruising easily |
These symptoms are not unique to CML. A doctor will need to use specific tests to decide whether a person has CML.
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How is chronic myeloid leukemia (CML) diagnosed?
The signs and symptoms of CML are common and can be confused with those of other conditions. People with these symptoms will often see the doctor to find out what's causing them. The doctor will want to know how long the symptoms have been present and will do a physical exam. He or she will check for signs of swelling in the liver, lymph nodes, and spleen.
The doctor may order a blood test called a complete blood count (CBC). This test shows how many white blood cells, red blood cells, and platelets there are in a patient's blood. The test can help the doctor decide whether a patient has CML.
To learn more, the doctor may take a sample of bone marrow. To do this, the doctor inserts a needle into a bone, such as the pelvic bone. Next, the doctor draws out some of the liquid marrow from the bone. Then, he or she will look at the bone marrow sample under a microscope. This can help find out what kind of leukemia the patient has.
Cytogenetic (si-toe-je-NEH-tick) analysis of the blood and bone marrow samples can show if the Philadelphia chromosome or other abnormalities are present. It can help confirm that the patient has CML.
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What is the goal of treatment for chronic myeloid leukemia (CML)?
The main goal of treatment for all types of leukemia, including CML, is complete remission (ree-MIH-shun). Remission means that there is no longer any sign of the disease. If someone with CML is in remission, blood tests show only healthy blood and bone marrow cells.
For people in the chronic phase of CML, the goal of treatment is to destroy all cells that have the Philadelphia chromosome. When this goal is reached, it is called a complete cytogenetic response.
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What drugs are used to treat CML?
Treatment for CML can be complex. No two patients are the same. There are several choices for drug therapy. Doctors can often treat the chronic phase of CML with certain drugs, such as the ones listed below.
Hydroxyurea and busulfan
These chemotherapy drugs have no effect on the chromosomes, and they do not stop the progression of the disease. However, they have been successful in lowering white blood cell counts, which can help reduce symptoms. They are most often used during the chronic phase.
Interferon-alpha
Interferon-alpha is a natural substance found in the body. A synthetic version is used to treat certain cancers. Doctors don't know exactly how it works in treating CML. They do know that it reduces the number of cells containing the Philadelphia chromosome in about 40% of people who have been treated with it. That effect gives some relief from symptoms. But because it does not destroy all the Philadelphia chromosomes, interferon-alpha does not appear to cure CML.
Molecular therapy
New medications are currently being used to target the underlying genetic mutation that causes CML. At this time, Health Canada has approved only one drug in this class, Gleevec (imatinib), based on unique findings from the clinical trials. Other drugs and combinations of drugs are still being tested and may be approved over the next few years. Talk with your doctor to learn more about the medications in this class.
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What other treatment choices do I have?
Right now, stem-cell transplants, called SCTs, offer people with CML the greatest chance for a cure. Stem-cell transplants get rid of all the Philadelphia chromosomes. However, stem-cell transplants can also have some severe side effects. The patient and doctor will need to compare risks and benefits before deciding on this treatment.
SCTs require a matching donor. Doctors will test a possible donor carefully to make sure that he or she has a closely matched tissue type to the patient. The donor may be closely related to the person with CML, such as a brother or sister, or the donor may be unrelated. In a process much like a blood transfusion, stem cells from the donor are put into the patient's bloodstream. Stem-cell transplantation most often is used in combination with high-dose chemotherapy and radiation to first destroy the patient's own marrow. This combination allows the donated stem cells to grow into healthy cells in the patient, but it can sometimes attack healthy cells and tissues.
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What questions can I ask my doctor about treating chronic myeloid leukemia (CML)?
If you or a loved one has been diagnosed with CML, you may find it helpful to write down any questions you want to discuss with the doctor before your next appointment. Here are a few suggestions to help you get started on your own list:
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What kind of leukemia do I have? |
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What are my treatment choices? |
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Which treatment do you think is best for me? Why? |
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How effective will that treatment be? |
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How often will my complete blood count be taken? What does this test mean? |
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Has cytogenetic testing been done on my blood and bone marrow samples? |
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How often will cytogenetic testing be done? |
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Will my treatment be changed based on my cytogenetic testing result? |
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How long will the treatment last? |
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What kind of side effects does the treatment have? |
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How can I manage the side effects? |
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Will I have pain, and if so, how can I relieve it? |
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How will treatment affect my daily activities? |
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Will other medications I am taking affect my treatment? |
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If this treatment doesn't work, what are my options? |
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