What is a BCR-ABL genetic test?

A BCR-ABL genetic test looks for a genetic mutation (change) on a specific chromosome.

Chromosomes are the parts of your cells that contain your genes. Genes are parts of DNA passed down from your mother and father. They carry information that determines your unique traits, such as height and eye color.

People normally have 46 chromosomes, divided into 23 pairs, in each cell. One of each pair of chromosomes comes from your mother, and the other pair comes from your father.

BCR-ABL is a mutation that is formed by the combination of two genes, known as BCR and ABL. It’s sometimes called a fusion gene.

• The BCR gene is normally on chromosome number 22.
• The ABL gene is normally on chromosome number 9.
• The BCR-ABL mutation happens when pieces of BCR and ABL genes break off and switch places.
• The piece of chromosome 9 that breaks off includes part of the ABL gene. When this piece moves over to chromosome 22, part of the ABL gene attaches to the BCR gene. The merged gene is called the BCR-ABL fusion gene. 
• The changed chromosome 22, which contains the BCR-ABL gene, is called the Philadelphia chromosome because that’s the city where researchers first discovered it.
• The BCR-ABL gene is not the type of mutation that is inherited from your parents. It is a type of somatic mutation, which means you are not born with it. You get it later in life.

The BCR-ABL gene shows up in patients with certain types of leukemia, a cancer of the bone marrow and white blood cells. BCR-ABL is found in almost all patients with a type of leukemia called chronic myeloid leukemia (CML). Another name for CML is chronic myelogenous leukemia. Both names refer to the same disease.

The BCR-ABL gene is also found in some patients with a form of acute lymphoblastic leukemia (ALL) and rarely in patients with acute myelogenous leukemia (AML).

Certain cancer medicines are especially effective in treating leukemia patients with the BCR-ABL gene mutation. These medicines also have fewer side effects than other cancer treatments. The same medicines are not effective in treating different types of leukemia or other cancers.

Other names: BCR-ABL1, BCR-ABL1 fusion, Philadelphia chromosome

What is it used for?

A BCR-ABL test is most often used to diagnose or rule out chronic myeloid leukemia (CML) or a specific form of acute lymphoblastic leukemia (ALL) called Ph-positive ALL. Ph-positive means a Philadelphia chromosome was found. The test is not used to diagnose other types of leukemia.

The test may also be used to:

• See if cancer treatment is effective.
• See if a patient has developed a resistance to certain treatment. That means a treatment that used to be effective is no longer working.

Why do I need a BCR-ABL genetic test?

You may need a BCR-ABL test if you have symptoms of chronic myeloid leukemia (CML) or Ph-positive acute lymphoblastic leukemia (ALL). These include:

• Fatigue
• Fever
• Weight loss
• Night sweats (excessive sweating while sleeping)
• Joint or bone pain

Some people with CML or Ph-positive ALL have no symptoms, or very mild symptoms, especially in the early stages of the disease. So your health care provider may order this test if a complete blood count or other blood test showed results that were not normal. You should also let your provider know if you have any symptoms that concern you. CML and Ph-positive ALL are easier to treat when found early.

You may also need this test if you are currently being treated for CML or Ph-positive ALL. The test can help your provider see if your treatment is working.

What happens during a BCR-ABL genetic test?

A BCR-ABL test is usually a blood test or a procedure called a bone marrow aspiration and biopsy.

If you are getting a blood test, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

If you are getting a bone marrow aspiration and biopsy, your procedure may include the following steps:

• You’ll lie down on your side or your stomach, depending on which bone will be used for testing. Most bone marrow tests are taken from the hip bone.
• Your body will be covered with cloth, so that only the area around the testing site is showing.
• The site will be cleaned with an antiseptic.
• You will get an injection of a numbing solution. It may sting.
• Once the area is numb, the health care provider will take the sample. You will need to lie very still during the tests.
  • For a bone marrow aspiration, which is usually performed first, the health care provider will insert a needle through the bone and pull out bone marrow fluid and cells. You may feel a sharp but brief pain when the needle is inserted.
  • For a bone marrow biopsy, the health care provider will use a special tool that twists into the bone to take out a sample of bone marrow tissue. You may feel some pressure on the site while the sample is being taken.
• It takes about 10 minutes to perform both tests.
• After the test, the health care provider will cover the site with a bandage.
• Plan to have someone drive you home, since you may be given a sedative before the tests, which may make you drowsy.

Will I need to do anything to prepare for the test?

You usually don’t need any special preparations for a blood or bone marrow test.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

After a bone marrow test, you may feel stiff or sore at the injection site. This usually goes away in a few days. Your health care provider may recommend or prescribe a pain reliever to help.

What do the results mean?

If your results show you have the BCR-ABL gene, as well as an abnormal amount of white blood cells, you will probably be diagnosed with chronic myeloid leukemia (CML) or Ph-positive, acute lymphoblastic leukemia (ALL).

If you are currently being treated for CML or Ph-positive ALL, your results may show:

• The amount of BCR-ABL in your blood or bone marrow is increasing. This may mean your treatment is not working and/or you’ve become resistant to a certain treatment.
• The amount of BCR-ABL in your blood or bone marrow is decreasing. This may mean your treatment is working.
• The amount of BCR-ABL in your blood or bone marrow has not increased or decreased. This may mean your disease is stable.

If you have questions about your results, talk to your health care provider.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about a BCR-ABL genetic test?

Treatments for chronic myeloid leukemia (CML) and Ph-positive, acute lymphoblastic leukemia (ALL) have been successful in patients with these forms of leukemia. It’s important to see your health care provider regularly to make sure your treatments continue to work. If you become resistant to treatment, your provider may recommend other types of cancer therapy.