BCR-ABL1 Genetic Test

What is a BCR-ABL1 genetic test?

A BCR-ABL1 genetic test uses a sample of blood or bone marrow to look for an abnormal gene called BCR-ABL1. This abnormal gene is found in certain types of blood cancer, such as chronic myeloid leukemia (CML).

Genes are parts of DNA in your cells that you inherit from your parents. You inherit two copies of each gene, one from each parent. Genes carry information that controls what you look like and how your body works. They also provide instructions for your cells to make proteins, which your body needs to work correctly.

However, some genes, including abnormal genes, can develop during your lifetime. These are called acquired gene changes. They can happen if cells make a mistake when dividing to make new cells or if your DNA is damaged from exposure to substances that cause cancer. Other times, the cause is unknown. The changes often show up only in certain types of cells. Changes in your genes are also called mutations or variants. 

The BCR-ABL1 gene is an example of an acquired gene change. This means you don't inherit it from your parents, and you can't pass it down to your children. It forms when a piece of one chromosome (chromosome 9) breaks off and fuses to another (chromosome 22). Chromosomes are tiny “packages” in your cells that contain your genes. Normally, you're born with a set of 46 chromosomes in each cell. The chromosomes are grouped into 23 pairs. Each pair has two chromosomes, one inherited from each parent.

Chromosome 9 contains the ABL1 gene. Chromosome 22 contains the BCR gene. So, when a piece of chromosome 9 breaks off and fuses to chromosome 22, part of the ABL1 gene fuses to the BCR gene, creating BCR-ABL1. The changed chromosome 22 is called a “Philadelphia chromosome” after the city where researchers discovered it. 

The abnormal BCR-ABL1 gene carries instructions for an abnormal protein called the BCR-ABL1 protein. This protein is too active and causes cells in your bone marrow to make large numbers of abnormal white blood cells. These cells grow and divide too much. When this happens, they can build up in the blood and bone marrow and crowd out healthy blood cells, leading to leukemia.

Your health care provider can use different types of BCR-ABL1 tests to see if you have the abnormal BCR-ABL1 gene. These check your blood or bone marrow and include:

• Molecular tests, such as PCR tests. These can look for genetic material made from the BCR-ABL1 gene in a sample of blood or bone marrow. They are sometimes called quantitative tests because they can measure how much of the BCR-ABL1 gene's material is in your blood or bone marrow.
• Chromosome testing. This test can look for the Philadelphia chromosome. 
• FISH (fluorescence in situ hybridization) testing. This test looks for specific changes in chromosomes or genes, including the change that forms BCR-ABL1.

Other names: BCR-ABL, BCR-ABL fusion, Philadelphia chromosome, B-cell acute lymphoblastic leukemia (B-ALL), chronic myelogenous leukemia (CML), t(9;22), BCR-ABL1 Transcript Detection by RT-PCR, Quantitative BCR-ABL1 Translocation Detection by RT-PCR 

What is it used for?

BCR-ABL1 genetic testing is most often used with other tests to help diagnose two specific types of blood cancer:

• Chronic myeloid leukemia (CML)
• Philadelphia-positive acute lymphoblastic leukemia (Ph+ ALL), a type of acute lymphoblastic leukemia that has the Philadelphia chromosome

Rarely, BCR-ABL1 is found in acute myeloid leukemia (AML). Testing for BCR-ABL1 may be used with other tests to help diagnose this type of AML.

BCR-ABL1 testing may also be used to help plan treatment. For example, people with a blood cancer that has the BCR-ABL1 gene may be treated with medicines called tyrosine kinase inhibitors (TKIs). These medicines are a type of targeted therapy. Targeted therapy uses medicines or other substances that mainly attack specific cancer cells and cause less harm to normal cells than cancer chemotherapy or radiation therapy do.

Quantitative (or molecular) BCR-ABL1 tests are also used to monitor treatment. Because these tests measure the amount of genetic material made from the BCR-ABL1 gene, your provider can compare the results over time to:

• See if cancer treatment is working
• Check for signs that the leukemia is no longer responding to treatment as expected
• Check for signs that the leukemia has come back

In certain cases, additional BCR-ABL1 testing can look for other changes that may make some medicines less effective. The results can help your provider decide whether your treatment needs to change.

Why do I need a BCR-ABL1 genetic test?

You may need a BCR-ABL1 genetic test if your provider thinks you may have a type of leukemia that involves the BCR-ABL1 gene. For example, your provider may test for the BCR-ABL1 gene if you had a complete blood count (CBC) that shows you have an unusually high number of white blood cells.

Some people with chronic myeloid leukemia (CML) have no symptoms when the disease is first found. If you do have symptoms, they may include:

• Fatigue
• Fever
• Weight loss for no known reason
• Night sweats (heavy sweating during sleep)
• Bone pain
• Pain or fullness below your ribs on the left side
• Painless lumps in your armpits, groin, neck, or belly

If tests have already shown that you have a type of leukemia that involves a BCR-ABL1 gene, you may need additional BCR-ABL1 tests so that your provider can:

• Make treatment decisions
• See how well your treatment is working (if treatment is helping, the number of cells with BCR-ABL1 genes will decrease)
• Monitor your health after treatment to see if blood cancer is coming back

What happens during a BCR-ABL1 genetic test?

A BCR-ABL1 genetic test usually uses a sample of blood or bone marrow.

If you are having 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 having a bone marrow test, a provider usually takes a sample from the back of the hip bone. You will be given an injection (shot) of medicine to numb the area. You may also be given medicine to help you relax or sleep.

A bone marrow test has two parts that are usually done one after the other:

• For a bone marrow aspiration, the provider pushes a thin needle into the bone and removes a sample of bone marrow fluid with a syringe attached to the needle. 
• For a bone marrow biopsy, the provider inserts a hollow needle into the bone and twists the needle to take out a small piece of bone marrow tissue. You may feel some pressure or brief pain while the sample is being taken.

The procedure takes only a few minutes. Afterwards, the area will be bandaged. You'll stay lying down for about 15 minutes to make sure the bleeding stops. You may need to stay longer if you had medicine to relax or sleep.

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

You usually don't need any special preparations for a blood test.

If you're having a bone marrow test, your provider will tell you whether you need to fast (not eat or drink) for a few hours before the procedure.

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 where the sample was taken. This usually goes away in a few days. If you need pain relief, talk with your provider.

What do the results mean?

If you had BCR-ABL1 genetic testing to diagnose a blood cancer, your provider will consider your results along with the results of other tests.

If BCR-ABL1 is found, it may be a sign that you have a blood cancer involving this gene change. Most people with chronic myeloid leukemia (CML) have BCR-ABL1. It is also found in Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) and, rarely, in certain other blood cancers.

If BCR-ABL1 is not found, CML is less likely. But in rare cases, a test may not detect an uncommon form of BCR-ABL1. Your provider will consider your results along with your symptoms and the results of other tests.

If you had a BCR-ABL1 gene test to see if your cancer treatment is working, your provider will compare your results with past test results to look for changes over time. In general:

• If the amount of BCR-ABL1 in your sample decreases, it usually means that the leukemia is responding to treatment. Your results may also describe how much the amount of BCR-ABL1 has decreased.
• If the amount of BCR-ABL1 in your sample increases, it may be a sign that the leukemia is not responding to treatment as expected or that it has come back. Your provider may order another BCR-ABL1 test or other tests before deciding whether your treatment needs to change.

Some laboratories may use different testing methods, especially if they need to use more specialized tests to look for less common types of BCR-ABL1. So, it's important to have your tests done the same way and usually in the same lab. If you have questions about how your results are compared, talk to your provider.

If your test does not detect BCR-ABL1, it doesn't necessarily mean that no leukemia cells remain. The amount of BCR-ABL1 may be too low for the test to detect.

The way your results are reported depends on which test you had. Ask your provider to explain what your test results mean for your health and treatment

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