Her-2/neu Testing

Also known as: c-erbB-2

Formal name: Human epidermal growth factor receptor

Related tests: Hormone Receptor Status; Tumour markers

At a Glance

Why Get Tested?

To determine whether a breast cancer tumour is positive for Her-2/neu, which helps to guide treatment and determine outcome

When to Get Tested?

If you have been diagnosed with invasive breast cancer and your doctor wants to determine whether the Her-2/neu gene is being over-expressed in the tumour

Sample Required?

A sample of breast cancer tissue obtained during a biopsy; sometimes a blood sample, taken from a vein in your arm, is also required

The Test Sample

What is being tested?

Her-2/neu is an oncogene. It codes for a receptor for a particular growth factor that causes cells to grow. Normal epithelial cells contain two copies of the Her-2/neu gene and produce low levels of the Her-2 protein on the surface of their cells. In about 20-30% of invasive breast cancers (and some other cancers, such as ovarian and bladder cancer), the Her-2/neu gene is amplified (far too many copies are produced) and its protein is over-expressed (an abnormally large amount of the protein is produced). Tumours that have this over-expression tend to grow more aggressively and resist hormonal therapy and some chemotherapies, and patients generally have a poorer outcome.

There are two main ways to test Her-2/neu status in cancer tissue: immunohistochemistry (IHC) and fluorescent in situ hybridization (FISH). IHC measures the amount of Her-2/neu protein present. FISH looks at the genetic level for actual gene amplification – the number of copies of the gene present. IHC is currently the most widely used initial testing method; however, if it is indeterminate or negative, then the FISH method is often done as a follow-up test.

How is the sample collected for testing?

A sample of breast cancer tissue is obtained by doing a fine needle aspiration, needle biopsy, or surgical biopsy. Her-2/neu protein sometimes is measured in a blood sample taken from a vein in the arm. The amount of Her-2/neu protein present in serum is loosely associated with the amount of cancer present; however it will not be positive until the tumour is fairly big and is not widely used for determining Her-2/neu status.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

The Test

How is it used?

Her-2/neu testing is primarily used to select patients for treatment with Herceptin (trastuzumab). It may also be used to help determine how aggressive a breast cancer tumour is likely to be.

It is also used as a predictor of response to certain types of chemotherapy and hormone therapy but these findings require further validation.

The serum Her2/neu test is sometimes used to monitor cancer therapy. If the level is initially elevated then falls, it is likely that treatment is working; if it stays elevated, treatment is not working; and if the level falls then rises, the cancer may be recurring.

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When is it requested?

Her-2/neu testing is recommended as part of an initial workup of invasive breast cancer and is sometimes done with recurrent breast cancer. It is not diagnostic but helps the doctor determine treatment options and understand more about the tumour’s characteristics.

Serum Her-2/neu is sometimes requested initially to establish a baseline and then, if elevated, used to monitor cancer treatment.

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What does the test result mean?

A positive tissue (IHC )Her-2/neu test means that the Her-2/neu gene is over-expressing (producing an excess amount of) Her-2/neu protein. If a FISH test is done, then amplification (production of too many copies) of the Her-2/Mneu gene can be detected. If either test is positive, the patient is likely to have an aggressive tumour. HER-2 positive patients are potential candidates for Herceptin therapy. [See "Is there anything else I should know?"].

Currently, Herceptin is only approved in the UK for the treatment of advanced breast cancer. In the future however, it is likely to be approved for the treatment of early breast cancer too.

If the IHC test is negative but the FISH test is positive, the patient still may benefit from Herceptin, but if both are negative the treatment will not be useful.

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Is there anything else I should know?

Her-2/neu-positive tumours may be susceptible to Herceptin (trastuzumab), a therapy created to target Her-2/neu protein. Herceptin, an antibody made in the laboratory, attaches itself to the excess protein molecules and inhibits the growth of the cancer. The development of this specialized therapy has increased the use of Her-2/neu testing. Herceptin may be used alone or with some chemotherapy agents but is only useful in those who have Her-2/neu amplification and protein over-expression.

Tissue Her-2/neu testing is not available in every laboratory. Both IHC and FISH require experience and special training to perform and interpret. Your doctor will probably send your sample to a reference laboratory and the results may take several weeks to return.

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Common Questions

1. Besides Her-2/neu, what other laboratory tests may my doctor request on my breast cancer tissue?

During an initial workup of invasive breast cancer, your doctor is likely to do a tissue test for hormone receptor status. A patient with a positive oestrogen and/or progesterone receptor status may find their response to endocrine or hormone therapy diminished if they are also Her-2/neu-positive, limiting that treatment option.

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2. Does Herceptin work for everyone who is Her-2/neu positive?

Unfortunately, no. Only about one-third of patients who are positive for Her-2/neu will respond to Herceptin therapy. There are other cellular factors involved that are not well understood yet. Herceptin is sometimes combined with other chemotherapy agents to make it more effective.

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.