Types of Breast Cancer: ER Positive, HER2 Positive, and Triple Negative
One major way of defining your type of breast cancer is whether or not it is:
- Hormone receptor (estrogen or progesterone receptor) positive
- HER2 positive
- Triple negative, not positive to receptors for estrogen, progesterone, or HER2.
These classifications provide doctors with valuable information about how the tumor acts and what kind of treatment may work best.
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In general, surgical and radiation treatments are similar for these different types of breast cancer. But drug treatments – such as chemotherapy, hormonal therapies, and other medications -- are usually different. These treatments are targeted to the specific type of cancer.
Hormone Receptor-Positive Breast Cancer
About 75% of all breast cancers are “ER positive.” They grow in response to the hormone estrogen. 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 estrogen or progesterone, your cancer is considered hormone-receptor positive and likely to respond to hormonal therapies.
Breast cancer tumors that are ER/PR-positive are 60% likely to respond to hormonal therapy. Tumors that are ER/PR negative are only 5% to 10% likely to respond to hormonal therapy.
Hormonal therapies for breast cancer are treatments usually taken after surgery, chemotherapy, and/or radiation are finished. They are designed to help prevent recurrence of the disease by blocking the effects of estrogen. 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 estrogen receptors on breast cancer cells and preventing estrogen from binding to them.
- A class of drugs called aromatase inhibitors actually stops estrogen production in post-menopausal women. These drugs cannot be taken by women who have not yet gone through menopause.
HER2-Positive Breast Cancer
In about 20% to 25% of breast cancers, the cancer cells make too much of a protein known as HER2/neu. These breast cancers tend to be much more aggressive and fast-growing.
For women with HER2-positive breast cancers, the drug Herceptin has been shown to dramatically reduce the risk of recurrence. It has now become standard treatment to give Herceptin along with adjuvant (after-surgery) chemotherapy or in those with metastatic breast cancer. Another drug, Tykerb, is often given for metastatic cancer if Herceptin fails.
Herceptin has far fewer immediate side effects than chemotherapy -- for example, there is usually no nausea or hair loss. However, there is a small but real risk of heart damage and possible lung damage. Scientists are still studying how long women should take Herceptin for the greatest benefit. Other drugs targeting the HER2 protein are also being developed.
Triple-Negative Breast Cancer
Some breast cancers -- estimates range between 10% and 17% -- -are known as “triple negative” because they lack estrogen and progesterone receptors and do not overexpress 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. Overall, however, they have a poorer prognosis than other types of breast cancer. So far, no targeted therapies like tamoxifen or Herceptin 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.
WebMD Medical Reference
Reviewed by
Arnold Wax, MD on February 18, 2010
© 2010 WebMD, LLC. All rights reserved.
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