Understanding ER/PR Testing
One of the most important ways of understanding and classifying breast cancers is their hormone receptor status. Breast cancers are either ER/PR (estrogen receptor/progesterone receptor) positive or negative. This means that the cells either require estrogen to reproduce and flourish (positive) or are not affected by the absence or presence of estrogen (negative). There may be prognostic implications of this classification, but it is especially important in treatment planning. Women who have Er/PR positive breast cancers always receive tamoxifen or one of the AIs as part of their systemic treatment. Women who have ER/PR negative tumors are rarely given these drugs as they are irrelevant to their situations. I am including an excellent summary and explanation from ASCO's Patient Site.
What to Know Patient Information Resources from ASCO
To help doctors give their patients the best possible care, the American Society of Clinical Oncology (ASCO) and the College of American Pathologists (CAP) developed evidence-based recommendations to improve the accuracy of testing for estrogen and progesterone receptors for breast cancer. This guide for patients is based on ASCO's and CAP's recommendations.
BACKGROUND About estrogen and progesterone receptors Estrogen receptors (ER) and progesterone receptors (PR; also called PgR) may be found in breast cancer cells. Cancer cells with these receptors depend on estrogen and related hormones, such as progesterone, to grow. Estrogen and progesterone influence many hormonal functions in women, such as breast development. If breast cancer cells have estrogen receptors, the cancer is called ER-positive breast cancer. If breast cancer cells have progesterone receptors, the cancer is called PR-positive breast cancer. If the cells do not have either of these two receptors, the cancer is called ER/ PR-negative. About two-thirds of breast cancers are ER and/ or PR positive.
About hormone therapy: Learning whether a tumor has estrogen and/or progesterone receptors helps doctors determine a patient's risk of recurrence (return of the cancer after treatment) and whether the cancer can be treated with hormone therapy. Hormone therapy blocks the tumor from using estrogen and/or progesterone for cancers that are ER and/or PR positive, slowing or stopping tumor growth. Two types of drugs may be used; one type called tamoxifen (Nolvadex) can be used for treatment.
KEY POINTS • Estrogen and progesterone receptors are found on breast cancer cells that depend on estrogen and related hormones to grow. • All patients with invasive breast cancer or a breast cancer recurrence should have their tumors tested for estrogen and progesterone receptors. • This testing should be performed by an accredited laboratory that follows specific testing procedures and handles the samples in a consistent way.
Other types of drugs called aromatase inhibitors (AIs) stop tissues and organs other than the ovaries from producing estrogen. AIs must never be used alone for women who have not gone through menopause. For women who have not gone through menopause, hormone therapy for ER and/or PR positive tumors may include stopping the production of estrogen and progesterone in the ovaries with surgery or injections.
Testing estrogen and progesterone receptors: Testing the tumor for both estrogen and progesterone receptors is a standard part of a breast cancer diagnosis. Because the results are used to guide treatment, it's important that the results be accurate. The most common method currently used to test a tumor for estrogen and progesterone receptors is called immunohistochemistry or IHC. IHC testing can detect estrogen and progesterone receptors in cancer cells from a sample of tissue. This tissue may come from a biopsy (removal of a small amount of tissue for examination under a microscope), or from the surgery to remove all of the tumor and some or all of the breast.
RECOMMENDATIONS: To improve the accuracy of ER and PR testing, ASCO and the CAP recommend the following: • The ER and PR status should be tested on the primary tumor and/or areas of spread (called metastases) for each patient newly diagnosed with invasive breast cancer or a breast cancer recurrence. • A tumor is ER and/or PR positive if at least 1% of the cells examined have estrogen and/ or progesterone receptors, and for such a tumor, patients should talk with their doctors about considering hormone therapy. • Testing is best done on larger tissue samples. If the cancer has spread, testing on those areas may be considered as well. • Laboratories testing for ER and PR should be accredited by the CAP or meet the additional accreditation requirements in the guideline and show agreement with other validated ER and PR tests for both positive and negative results. The laboratory must also be inspected every two years to be sure that the testing methods conform to the guideline requirements.
WHAT THIS MEANS FOR PATIENTS Because the results of ER and PR testing can make a difference in a patient's treatment and chance of recurrence, it's important that these tests are accurate. This guideline was developed to help both doctors and laboratories know how to improve the accuracy of ER and PR testing for patients with breast cancer.
QUESTIONS TO ASK THE DOCTOR: To learn more about estrogen and progesterone receptor testing for breast cancer, consider asking your doctor the following questions: • What are the results of the ER and PR tests on my tumor sample? What do they mean? • Does this laboratory meet the standard guidelines like those from ASCO and the CAP? • Is a board-certified pathologist on my treatment team? • Do you know if this is an experienced lab and if my tissue was quickly given to the pathologist after my biopsy or surgery as recommended by guidelines? • Can I obtain a copy of my pathology report (laboratory test results)? • Is my ER and PR status indicated on the pathology report? Was the ASCO-CAP guideline recommendation used to define the status? • Based on these test results, what treatments do you recommend and why? • What are the possible side effects of these treatments?
Understanding the ER/PR status of the primary tumor and any recurrent tumors can help doctors make sure that patients receive the appropriate treatment and avoid side effects of a treatment that may not work. Use this guideline to talk with your doctor about the accuracy of your ER and PR test results and what that means for your treatment.