All breast cancers are tested for oestrogen, progesterone and HER2 receptors.
The results of these tests will indicate whether certain treatments, particularly hormone therapy and targeted treatments, might be appropriate for you based on the receptor status of your breast cancer. You will receive your receptor status information in your pathology report.
Hormone receptor status
Oestrogen and progesterone receptors are proteins found on the surface of breast cells. These receptors are present in healthy breast cells and help control the way breast cells grow, but in 70% of breast cancers, the receptors are over-expressed. These cancers are called hormone sensitive or hormone receptor-positive, meaning that oestrogen and progesterone can attach to the receptors and fuel the growth of the cancer. Hormone sensitive breast cancers may be:
- both oestrogen receptor-positive and progesterone receptor-positive (ER+, PR+)
- oestrogen receptor-positive only (ER+, PR -)
- progesterone receptor-positive only (ER-, PR+)
Even if the cancer cells show just a low level of hormone sensitivity, hormone therapy can help reduce the risk of the cancer recurring by preventing oestrogen from stimulating growth of the cancer cells.
Oestrogen receptor-negative (ER-, PR-) cancers have few or no hormone receptors so they don't respond to hormone therapy.
It's now known that some breast cancers can change their hormone receptor status over time, changing from positive to negative or vice versa. If the cancer recurs then the tests will be performed again.
The HER2 (Human Epidermal Growth Factor Receptor 2) gene has a role in controlling the growth of normal breast cells. The gene is also known as HER2/neu or ERBB2 and it makes proteins (receptors) which are located on the surface of breast cells. However, in about 20% of breast cancers the gene makes too many copies of itself. This is called HER2 amplification and it leads to too many HER2 receptors being created. This over-expression of the receptors results in cancer cells dividing and growing at a much faster rate.
HER2-positive breast cancer is any type of breast cancer which tests positive for HER2 over-expression.
HER2-positive breast cancers tend to be more aggressive than HER2-negative cancers and are often less sensitive to hormone therapy. HER2-positive disease previously carried a bleak prognosis, but the development of targeted treatments has significantly improved outcomes. For example, chemotherapy and Herceptin (a treatment which specifically targets the HER2 receptor), administered together has been shown to reduce the risk of recurrence by up to half compared to treatment with chemotherapy alone.
Treatment for early HER2-positive breast cancer generally involves surgery, chemotherapy and Herceptin, and may include radiation therapy and hormonal therapy.
Triple-negative breast cancer
Triple-negative breast cancer (TNBC) is breast cancer that tests negative for all three receptors (oestrogen, progesterone, and HER2). About 15% of breast cancers are triple-negative. This type tends to occur more commonly in pre-menopausal women and people with a faulty BRCA1 gene. New Zealand statistics show that Pacific, Maori and Asian women have a higher incidence of triple-negative breast cancer than Caucasian women .
People with TNBC don't benefit from treatment with tamoxifen, aromatase inhibitors, or Herceptin as the cancers lack the receptors which these treatments target. There are currently no specifically targeted treatments for this form of breast cancer although many new drugs are being investigated in clinical trials. Treatment consists of surgery, chemotherapy and often radiation therapy.
In most cases, TNBC is very responsive to chemotherapy, which can be given either before or after surgery. Triple-negative disease has a higher risk of recurring outside the breast in the first two to five years but a lesser risk after five to eight years compared to other forms of breast cancer.
Download The Triple Negative Foundation’s PDF:
Guide to Understanding Triple Negative Breast Cancer