Summary

If you have breast cancer or one of certain stomach or oesophageal cancers your surgeon or oncologist may send a sample of your tumour to the laboratory so the tumour’s DNA can be tested to see if there is an HER-2 genetic mutation. If your tumour is found to have a mutation it is HER-2 positive and you may benefit from the HER2-targeted treatment, Herceptin (trastuzumab). 

Why get tested?

HER-2 stands for human epidermal growth factor receptor 2. This is a gene that codes for a particular growth factor receptor which is part of normal cell growth. In HER-2 positive cancers there are too many gene copies which causes cancer cells to grow quickly.

In the past, HER-2-positive breast cancers were associated with an increased risk of recurrence and a poorer outcome. However, the use of Herceptin (trastuzumab) a targeted treatment against HER-2 positive cancers, together with chemotherapy has dramatically improved outcomes for HER-positive breasts cancer stomach and oesophageal cancers.

Herceptin blocks the ability of the cancer cells to receive chemical signals that tell the cells to grow.  Currently, it is approved in Australia for the treatment of HER2 positive early-stage breast cancer and HER2 positive advanced breast cancer. It has also been approved for use in advanced cancers of the stomach or lower oesophagus if they are shown to be HER-2 positive.

HER-2 testing cannot diagnose cancer but helps your doctor understand more about the tumour’s characteristics and make decisions about treatment.

Most HER-2 testing involves taking a sample of tumour tissue using a fine needle aspiration, needle biopsy or surgical biopsy.

An HER-2 blood test is sometimes used to monitor cancer treatment. An initial test establishes a baseline and then tests are repeated to see if this changes.

What is HER-2?

The HER-2 gene codes for a particular growth factor receptor on the surface of cells that sends signals to the nucleus enabling cells to grow. It is known as an oncogene. Normally, an oncogene turns on cell growth as needed but if there is a mutation and the gene isn’t working properly there is uncontrolled cell growth which can lead to cancer.

Normal cells contain two copies of the HER-2 gene and produce low levels of the protein. In about 20 to 30 per cent of invasive breast cancers and some other cancers, including certain stomach and oesophageal cancers, far too many copies of the HER-2 gene are made. The result is that an abnormally large amount of the HER-2 protein is produced  – said to be over-expressed. Cancers that have this over-expression are known as HER-2-positive. HER-2-positive tumours tend to grow more aggressively and respond differently to treatment than HER2-negative tumours.

Two types of tests
There are two main ways to test HER-2 status in cancer tissue. These are immunohistochemistry (IHC) and fluorescence in situ hybridisation (FISH). IHC measures the amount of HER-2 protein present. FISH looks at the genetic level for actual gene production – the number of copies of the HER-2 gene.

Having the test

Sample 
Most HER-2 testing involves taking a sample of tumour tissue using a fine needle aspiration, needle biopsy or surgical biopsy. When used to monitor treatment a blood sample is used.

Any preparation?
None
 

Your results

Diagnosis
A positive HER-2 IHC test means that the HER-2 gene is over-expressing – producing an excess amount of HER-2 protein. A positive FISH test means that there are too many copies of the HER-2 gene being produced. If you are HER2-positive you are a potential candidate for HER-2 targeted therapy such as Herceptin (trastuzumab). 
Monitoring
The HER-2 test is also sometimes used to monitor cancer therapy. If the level is initially raised then it falls, it is likely that treatment is working. If it stays higher, treatment is not working. If the level falls, then rises, the cancer may be recurring.

Herceptin (trastuzumab) is a therapy created to target HER-2 protein. Herceptin, an antibody made in the laboratory, attaches itself to the excess protein molecules and inhibits the growth of the cancer. Herceptin may be used alone or with some chemotherapy agents.

Tissue HER2 testing is not available in every laboratory. Both IHC and FISH require experience and special training to perform and to interpret.
 

More information

Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.

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