Types of breast cancer: ER positive, HER2 positive and triple negative
Diagnosing the type of breast cancer a woman has is important for doctors when choosing the treatment approach.
Breast cancers can be:
Some medication for breast cancer only works with one of these types. For example trastuzumab, also known as Herceptin, is only effective for HER2 breast cancer.
Hormone receptor-positive breast cancer
About 75% of all breast cancers are "ER positive". They grow in response to the hormone oestrogen. About 65% of these are also "PR positive". They grow in response to another hormone, progesterone.
If your breast cancer’s cells have a significant number of receptors for either oestrogen or progesterone, your cancer is considered hormone-receptor positive and will likely to respond to hormonal therapies.
Breast cancer tumours that are ER/PR-positive are 60% likely to respond to hormonal therapy. Tumours that are ER/PR negative are only 5% to 10% likely to respond to hormonal therapy.
Hormonal therapies for breast cancer are treatments used after surgery, chemotherapy, and/or radiotherapy are finished. They are designed to help prevent recurrence of the disease by blocking the effects of oestrogen. They do this in one of several ways.
- The drug tamoxifen, taken by some women for up to five years after initial treatment for breast cancer, helps prevent recurrence by blocking the oestrogen receptors on breast cancer cells and preventing oestrogen from binding to them.
- A class of medicines called aromatase inhibitors actually stops oestrogen production in post- menopausal women. These medicines cannot be taken by women who have not yet gone through menopause.
HER2-positive breast cancer
In about 20% of breast cancers, the cancer cells make too much of a protein known as HER2. These breast cancers tend to be much more aggressive and are fast-growing.
For women with HER2-positive breast cancers the medicine trastuzumab has been shown to dramatically reduce the risk of recurrence. It is approved for NHS treatment for some people with early and advanced breast cancer. The drug lapatinib may also be used for metastatic breast cancer.
Trastuzumab has far fewer immediate side effects than chemotherapy - there is usually no nausea or hair loss for example. However there is a small but real risk of heart damage and possible lung damage. Scientists are still studying how long women should take trastuzumab for the greatest benefit. Other medicines targeting the HER2 protein are also being developed.
Triple-negative breast cancer
Some breast cancers - estimates range between 15% and 20% - are known as "triple negative" because they lack oestrogen and progesterone receptors and do not have too much of the HER2 protein. The majority of breast cancers associated with the breast cancer gene known as BRCA1 are triple negative.
These cancers generally respond well to adjuvant chemotherapy. However they have a poorer prognosis than other types of breast cancer. So far, no targeted therapies such as tamoxifen or trastuzumab have been developed to help prevent recurrence in women with triple-negative breast cancer. Cancer experts are studying several promising targeted strategies aimed at triple-negative breast cancer.