You might hear your doctor call this type of test a tumour profiling test, a gene expression profiling (GEP) test, a gene expression analysis test, or a gene assay.
Examples include EndoPredict (EPclin score), Oncotype DX Breast Recurrence Score and Prosigna.
What these tests are not
GEP tests look for abnormalities in gene activity within cancer cells, not genes in normal body cells.
They should not be confused with tests that look for an inherited faulty gene that increases a person’s risk of getting cancer in the first place.
GEP tests are also different to other tests that show whether your cancer is likely to respond to a particular drug. This is generally known as personalised medicine.
GEP tests are a step towards personalised medicine because they help a doctor to decide who needs further treatment in general. But personalised medicine tests show whether cancer cells have a particular protein that means a specific drug is likely to work.
An example of this is the Her2 test, this shows whether your breast cancer is likely to respond to trastuzumab (Herceptin).
How GEP tests work
GEP tests look at groups of cancer genes to find out how active they are. The activity of particular genes helps the doctor predict whether a cancer is likely to come back. This in turn can help them decide who needs extra treatment to lower the risk of their cancer coming back.
For example, you might not need to have chemotherapy if the risk of the cancer coming back after surgery and radiotherapy is low. Your doctor is more likely to recommend chemotherapy if the chance of the cancer coming back is higher.
It is important that people don’t have unnecessary treatments, because all treatment have some side effects.
In many cases, it is clear to a specialist whether a patient definitely does or does not need further treatment. So these tests might be most useful where there is some uncertainty about the risk of your cancer coming back.
GEP tests for breast cancer
There a number of GEP tests. The National Institute for Health and Clinical Excellence (NICE) has assessed some of these. It recommends that the following tests should be an option for some people with breast cancer to help decide whether chemotherapy is needed after surgery:
- EndoPredict (EPclin score)
- Oncotype DX Breast Recurrence Score
NICE recommend these tests for people with intermediate grade breast cancer with all of the following:
- stage 1 or 2 disease (early breast cancer)
- no cancer cells in the lymph nodes
- oestrogen receptors in their cancer cells (oestrogen receptor positive)
- their cancer cells have a small number of HER2 receptors (HER2 negative)
Scoring the cancer
Doctors carry out these tests on the cancer after it has been removed with surgery. They look at a group of genes in the cancer cells to find out how they are behaving. The cancer is then given a score. The lower the score, the lower the risk of the cancer coming back. The higher the score, the higher the risk.
Doctors would recommend chemotherapy to people with a higher score. But they wouldn’t usually recommend it to those with a low score.
NICE also looked at two other tests, but has not recommended them:
- IHC4+C – as there is not enough evidence to show that it is reliable
- Mamma Print – because it is not cost effective
NICE only covers England and Wales. Your cancer specialist will be able to tell you if GEP testing is available if you live in Scotland or Northern Ireland.
Are GEP tests available for other cancer types?
GEP tests are not widely available and are still used mainly within research. They are still in the early stages of development for most types of cancer. It takes time for scientists to develop these tests, to make sure that they work and that they are accurate and cost effective.
The tests have to be different for each type of cancer. For example, the gene activity in the cells of a breast cancer is different to the cells of a bowel cancer. Even within one type of cancer it might be necessary to develop different tests for different stages of that cancer.
Researchers have been looking into GEP tests for different cancers including breast cancer, bowel cancer, food pipe (oesophageal) cancer and stomach cancer.