What is Estrogen Receptor, Progesterone Receptor Breast Cancer Testing?

Also Known As: Estrogen Receptors, Progesterone Receptors, ER and PR Status, Hormone Receptor Status

Formal Name: Estrogen and Progesterone Receptor Status

Receptors are specialized proteins on the surface of or within cells that bind to specific substances. The binding typically has a specific effect on the cells. Many, but not all, breast cancer cells have receptors that bind to the hormones estrogen and/or progesterone. Breast cancer tumors with estrogen receptors (ER) and/or progesterone receptors (PR) typically depend on the hormones to grow and divide. ER and PR testing of breast tumor tissue determine if one or both types of receptors are present. About two out of three breast cancers are positive for ER and PR.

How is the test used?

Hormone receptor testing of breast tumor tissue is used to determine if estrogen receptors (ER) and/or progesterone receptors (PR) are present and whether the tumor tissues depend on estrogen and/or progesterone to grow. Knowing if a tumor grows under the influence of hormones indicates whether removal of one’s ovaries, which produce the hormones, or blocking the hormones with drugs (hormone therapy or endocrine therapy) can inhibit tumor growth to prolong survival. Studies have demonstrated a benefit from such hormone therapy for patients with ER-positive tumors.

Hormone Receptor-Positive Breast Cancer

About 80% of all breast cancers are “ER-positive.” That means the cancer cells 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 has a significant number of receptors for either estrogen or progesterone, it’s considered hormone-receptor-positive.
Tumors that are ER/PR-positive are much more likely to respond to hormone therapy than tumors that are ER/PR-negative.
You may have hormone therapy after surgery, chemotherapy, and radiation are finished. These treatments can help prevent a return of the disease by blocking the effects of estrogen. They do this in one of several ways.

• The medication tamoxifen (Nolvadex) helps stop cancer from coming back by blocking hormone receptors, preventing hormones from binding to them. It’s sometimes taken up to 5 years after initial treatment for breast cancer.
• A class of medicines called aromatase inhibitors actually stops estrogen production. These include anastrozole (Arimidex), exemestane (Aromasin), and letrozole (Femara). They’re only used in women who’ve already gone through menopause. Fulvestrant (Faslodex) is a medication that blocks and damages estrogen receptors that are sometimes used in the treatment of metastatic breast cancer. Toremifene (Fareston) is a drug that blocks estrogen receptors that can also be given to certain women with metastatic breast cancer.
• CDK 4/6 inhibitors abemaciclib (Verzenio), palbociclib (Ibrance), and ribociclib (Kisqali) are sometimes used with aromatase inhibitors or the hormone therapy fulvestrant (Faslodex).

Learn more about hormone therapy to treat breast cancer.

HER2-Positive Breast Cancer

In about 20% of breast cancers, the cells make too much of a protein known as HER2. These cancers tend to be aggressive and fast-growing.

For women with HER2-positive breast cancers, the targeted drug trastuzumab (Herceptin) has been shown to dramatically reduce the risk of cancer coming back. It‘s the standard treatment to give this medication along with chemotherapy after surgery to people with breast cancer that’s spread to other areas. It can also be used for early-stage breast cancer. But there is a small but real risk of heart damage and possible lung damage.

There are several other targeted therapies sometimes used in the treatment of HER2-positive breast cancer. These include:

• Ado-trastuzumab emtansine (Kadcyla)
• Fam-trastuzumab deruxtecan-nxki (Enhertu)
• Lapatinib (Tykerb)
• Margetuximab (Margenza)
• Neratinib (Nerlynx)
• Pertuzumab (Perjeta)
• Tucatinib (Tukysa)

Read more on HER2-positive breast cancer causes, symptoms, and treatment.

Triple-Negative Breast Cancer

Some breast cancers -- between 10% and 20% -- are known as “triple-negative” because they don’t have estrogen and progesterone receptors and don’t overexpress the HER2 protein. Many breast cancers associated with the gene BRCA1 are triple-negative. They are often treated with surgery, chemotherapy, and radiation.

Olaparib (Lynparza) and talazoparib (Talzenna) are targeted therapy medicines that can be used to treat women with a BRCA mutation who have metastatic HER2-negative breast cancer. These drugs block a protein called PARP. Atezolizumab (Tecentriq) is an immunotherapy drug used in combination with the chemotherapy nab-paclitaxel (Abraxane) to block a protein called PD-L1 in certain breast cancers that are triple-negative. Get an overview of triple-negative breast cancer symptoms and treatment.