Genetic tests on your chronic lymphocytic leukaemia (CLL) cells

Your doctors do tests on your blood and bone marrow to look for changes in certain genes . This information helps them to decide which treatment is best for you. It can also help them decide when you need to start treatment.

You might hear these tests called cytogenetic tests or molecular analysis. The doctors are looking for changes in genes and chromosomes in the leukaemia cells.  

This is different to testing you to see if you have an inherited faulty gene that increases your risk of getting cancer in the first place. These genetic tests on your leukaemia cells should not be confused with tests that look for an inherited faulty gene.

Why you might have these tests

You might have these genetic tests on your leukaemia cells when you are first diagnosed with CLL. The results of these tests:

• help doctors decide which type of drug might help you if you need to have treatment
• provide information about how your CLL might behave. This helps your doctor talk to you about your outlook (prognosis)

You might need to have some genetic tests only once as the results won’t change. But the doctors repeat some tests if your CLL progresses. Again this can help them to decide about the best treatment. This is because some genes might change over time. This is called mutating.

Types of tests

There are different types of tests.

FISH tests and other tests to look for structural changes in genes

One type is called a FISH test. FISH stands for fluorescent in situ hybridization. The FISH technique uses a special fluorescent dye. This makes it easier to see particular gene and chromosome changes.

Doctors use the FISH test to look for changes to chromosomes and genes. This includes whether part of a chromosome is missing (deleted). For example, in CLL, doctors look very carefully for deletions in chromosome 17. They also look for other structural changes - for example changes in chromosomes 11,12 and 13.

Other molecular tests

DNA sequencing is another way to look for gene changes. In CLL, doctors use this test to look for faults (mutations) in certain genes. For example, they look for faults in the TP53 gene.

Doctors might also look at how many faults (mutations) are in the IGHV gene. This helps them decide if your CLL is “mutated” or “unmutated”.

What happens

You might not need any extra tests. The doctor can do genetic tests on blood samples. You have blood tests when you are diagnosed, and before each treatment.

Or they can test your bone marrow sample if you have had a bone marrow test. Your doctor will tell you if you need to have any extra tests.

Understanding your results

You might hear or read that your CLL:

• has a TP53 mutation (mutated TP53) – this means there are changes in the TP53 gene
• is del 17p or has a p53 deletion / mutation – this means part of chromosome 17 is missing (deleted)
• has an IGHV mutation (mutated IGHV) – this means there are changes in the IGHV gene
• does not have an IGHV mutation (unmutated IGHV) – this means there are no changes in the IGHV gene
• has other structural changes or mutations

Your doctor might tell you that your genetic tests don’t show any abnormalities. This means the doctor hasn’t found any changes. But this might be because they are too small to find. Another reason could be there might be gene changes that researchers haven’t discovered yet. So a ‘normal’ result doesn’t necessarily mean you don’t have any abnormal genes.

Your doctor will talk with you about any other changes and what they mean. For example, they might find changes such as a deletion in chromosome 13. If they find this on its own, it often means that your CLL will not progress and you don't need treatment.

Your doctor will talk to you about whether you need to have treatment. This also depends on many different factors such as the stage of your CLL and what symptoms you have.

If you have a TP53 mutation / del 17p and need treatment

You won’t have chemotherapy. This is because doctors know that chemotherapy doesn’t work as well for people with this gene mutation. Your doctor will talk to you about your other treatment options.

If you have an IGHV mutation and need treatment

People with faulty (mutated) IGHV often never need treatment. If you do need treatment, you might have chemotherapy as well as immunotherapy treatment. 

People with faulty IGHV, who don't have any other gene changes, often respond well to all treatments. For some people, the treatment can control the CLL for a long period of time.

If you don’t have an IGHV mutation (unmutated IGHV) and need treatment

Your doctor will talk to you about your treatment options. Some treatments might not work as well if your CLL cells have an unmutated IGHV gene. This is when you compare it to people with a mutated IGHV gene.