Hormone receptor status
Some breast cancer cells need estrogen and/or progesterone (hormones produced in the body) to grow. These cancer cells have special proteins inside, called hormone receptors.
When hormones attach to hormone receptors, the cancer cells with these receptors grow.
A pathologist determines the hormone receptor status by testing the tumor tissue removed during a biopsy. The standard of care is to test all breast cancers for hormone receptor status.
- Hormone receptor-positive tumors are estrogen receptor-positive (ER-positive) and progesterone receptor-positive (PR-positive). These tumors express hormone receptors. This means they have a lot of hormone receptors.
- Hormone receptor-negative tumors are estrogen receptor-negative (ER-negative) and progesterone receptor-negative (PR- negative). These tumors do not express hormone receptors. This means they have few or no hormone receptors.
About 70-80 percent of breast cancers are hormone receptor-positive [18,29].
Hormone receptor status is part of breast cancer staging and helps guide your treatment.
You may hear the term “biomarker” to describe hormone receptors. A biomarker is any molecule in your body (here, in the breast cancer tissue removed during surgery) that can be measured and gives information about your health. In this case, hormone receptor status gives information about your breast cancer.
Hormone receptor status and hormone therapy
Hormone receptor-positive breast cancers can be treated with hormone therapies.
Hormone therapy drugs include tamoxifen and the aromatase inhibitors, anastrozole (Arimidex), letrozole (Femara) and exemestane (Aromasin). Ovarian suppression, with surgery or drug therapy, is also a hormone therapy.
Hormone receptor-negative breast cancers are not treated with hormone therapies because they don’t have hormone receptors.
Estrogen receptor status and progesterone receptor status
Breast cancers that are ER-positive tend to be PR-positive. And, cancers that are ER-negative tend to be PR-negative.
How do hormone therapies work?
Hormone therapies slow or stop the growth of hormone receptor-positive tumors by preventing the cancer cells from getting the hormones they need to grow.
They work in a few ways:
- Some hormone therapies, such as tamoxifen, attach to the hormone receptor in the cancer cell and block estrogen from attaching to the hormone receptor.
- Some hormone therapies, such as aromatase inhibitors and ovarian suppression, lower the level of estrogen in the body so the cancer cells can’t get the estrogen they need to grow.
Hormone receptor status and early breast cancer prognosis
Hormone receptor status is related to the risk of breast cancer recurrence.
Hormone receptor-positive tumors have a slightly lower risk of breast cancer recurrence than hormone receptor-negative tumors in the first 5 years after diagnosis .
After about 5 years, this difference begins to decrease and over time, goes away .
For a summary of research studies on hormone receptor status and survival, visit the Breast Cancer Research Studies section.
HER2 (human epidermal growth factor receptor 2) is a protein that appears on the surface of some breast cancer cells. It may also be called HER2/neu or ErbB2.
The HER2 protein is an important part of the pathway for cell growth and survival.
- HER2-positive breast cancer cells have a lot of HER2 protein. You may also hear the term HER2 over-expression.
- HER2-negative breast cancer cells have little or no HER2 protein.
About 10-20 percent of newly diagnosed breast cancers are HER2-positive [18,30].
HER2 status is part of breast cancer staging and helps guide your treatment.
You may hear the term “biomarker” to describe HER2. A biomarker is any molecule in your body (here, in the breast cancer tissue removed during surgery) that can be measured and gives information about your health. In this case, HER2 status gives information about your breast cancer.
Learn about HER2 status information on a pathology report.
Testing for HER2 status
The standard of care is to test all breast cancers for HER2 status.
The main tests for HER2 status are:
- Immunohistochemistry (IHC), which detects the number of HER2 protein receptors on the cancer cells
- Fluorescence in situ hybridization (FISH), which detects the number of HER2 genes in the cancer cells
HER2-positive cancers and HER2-targeted therapies
HER2-positive breast cancers can be treated with HER2-targeted therapies, such as trastuzumab (Herceptin). These drug therapies target the HER2 receptor.
Trastuzumab and other HER2-targeted therapies are not used for HER2-negative cancers.
Proliferation rate is the percentage of cancer cells actively dividing.
In general, the higher the proliferation rate, the more aggressive the tumor tends to be and the more likely it is to spread to other parts of the body.
Tumors with a high proliferation rate (those that are growing fast) often have a poorer prognosis than those with a low proliferation rate.
Proliferation rate could be a good predictor of prognosis and whether or not a tumor will respond to chemotherapy. However, there are issues related to the measurement of proliferation rate.
Some medical centers assess proliferation rate, but it’s not standard. Proliferation rate isn’t routinely used by all health care providers to guide treatment.
The Ki-67 test is a common way to measure proliferation rate. When cells are growing and dividing (proliferating), they make proteins called proliferation antigens. Ki-67 is a proliferation antigen.
The result of this test is reported as the percentage of tumor cells with Ki-67 antigen. The higher the percentage, the more aggressive the tumor tends to be.
If abemaciclib is being considered for your treatment plan, Ki-67 testing may be done on your tumor. Hormone receptor-positive breast cancers that have a Ki-67 score of 20 percent or higher, as well as other tumor factors, may be treated with abemaciclib.
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