Estrogen Receptor, Progesterone Receptor Breast Cancer Testing
The healthcare practitioner who will obtain the sample for testing will provide instructions for how to prepare for the procedure.
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 determines 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.
When is it ordered?
In 2010, the American Society of Clinical Oncology (ASCO) and the College of American Pathologists (CAP) jointly published guidelines that recommend that all tumors from individuals with newly diagnosed invasive breast cancer be evaluated for estrogen and progesterone receptors. The guidelines also state that all recurrent breast cancers should be tested and that the option of testing should be provided for patients who have non-invasive breast cancer.
A 2015 ASCO Clinical Practice Guideline reaffirmed that retesting of metastatic tumors for ER and PR receptors should be offered, although it is unclear whether changing treatment on the basis of a change in receptor test results affects clinical outcomes.
The 2017 NCCN guideline for breast cancer also recommends ER testing for ER and PR for invasive breast cancer.
What does the test result mean?
The results for ER receptor and PR receptor testing cover a range from low to high levels of receptor expression. Patients receive greater benefit from hormone therapy if their breast tumor has more ER receptors. Studies indicate that tumors with less receptor expression are less likely to respond to the therapies that aim to reduce stimulation of the receptors such as tamoxifen, but even low positivity may be associated with some response. The more receptors present, the more likely the response.
Guidelines recommend classifying tumors with as few as 1% positive cells as receptor positive, but for tumors with low ER expression, the decision for targeted therapy should be based on an analysis of its risks versus potential benefits. If a person's cancer is ER-negative but PR-positive, or ER-positive but PR-negative, then the person may still benefit from hormone therapy.
If the cancer is both ER-negative and PR-negative, then the person is not likely to benefit from hormone therapy.
An individual's response to hormone therapy will depend on a variety of factors, but typical approximate response rates include:
- ER-positive, PR-positive: 75-80%
- ER-positive, PR-negative: 40-50%
- ER-negative, PR-positive: 25-30%
- ER-negative, PR-negative: 10% or less
If there is a discrepancy between test results after testing a primary and a metastatic tumor sample, many times the ER and PR status of the metastasis can be used to guide therapy when considered in the context of the clinical scenario and your treatment goals.
What other testing might be done?
HER2 testing is typically done at the same time as hormone receptor status testing. Additional treatment options are possible for tumors that are HER2-positive and these cancers may benefit from anti-HER2 therapy regardless of hormone receptor status. Also, a healthcare practitioner may decide on a case-by-case basis whether to offer breast cancer gene expression profiling and, based on the results (as well as other factors), whether to offer additional treatment.
I was diagnosed with ductal-carcinoma in situ. Will hormone receptor testing be done?
When you have been diagnosed with ductal-carcinoma in situ (DCIS, cancer confined to the breast ducts), you and your physician may choose to determine estrogen receptor status depending upon your treatment preferences. The 2017 NCCN guideline for breast cancer recommends ER testing DCIS. Results of ER testing of DCIS can help determine whether there may be an opportunity for adjuvant hormone therapy and reducing risk for recurrence or progression to invasive breast cancer.
How long will it take for results?
Hormone receptor status testing is not available in every laboratory. It requires experience and special training to perform and interpret. A healthcare practitioner will often send a sample to a reference laboratory and it may take several days to weeks before the results are available. It is recommended that testing be done by a lab that follows the American Society of Clinical Oncology/College of American Pathologists Guideline Recommendations to avoid inaccurate results.
Can a blood sample be used instead of a tissue sample to perform these tests?
Would this testing also be performed on a man?
Is there anything else I should know?
It takes a small amount of cancer tissue to perform hormone receptor status testing. If a sufficient sample is not available, your healthcare practitioner may make an assumption that your cancer is ER-positive and PR-positive in order to broaden the treatment options. However, for women with ER-negative invasive breast cancer, studies have demonstrated no benefit from endocrine treatments.
While uncommon, truly ER-negative but PR-positive invasive breast tumors are also considered eligible for hormone therapy. Receptor status may provide some information about prognosis.
You may obtain a copy of your ER and PR test report and review the results with your healthcare practitioner to fully understand the results.