Hormone Receptor-Positive Breast Cancer
Hormone receptor-positive, or HR-positive, breast cancer grows in response to the hormones estrogen and progesterone. These hormones occur naturally in the body and prompt cell action in our system in different ways.
If your doctor recommends hormonal therapy as part of your breast cancer treatment, you may be confused. You may have heard that hormones that occur naturally in the body are a risk factor in breast cancer. Or that hormone replacement therapy, or HRT, is used to treat symptoms of menopause that are caused by the body’s dwindling supply of hormones.
Hormonal therapy for breast cancer, which is different than HRT, is used to treat cancers that are hormone receptor-positive based on tests in your pathology report. This means that the cancer cells have receptors for either of two hormones that occur naturally in the body: the estrogen receptor (ER), progesterone receptor (PR), or both. Your doctor uses hormonal therapy to treat hormone receptor-positive breast cancer.
To understand the goal of hormonal therapy, it helps to be familiar with what hormones do.
Our bodies naturally make hormones such as
These hormones prompt cell action in our system in different ways. They are all important for good health.
Estrogen has multiples roles. It helps sex organs develop, makes pregnancy possible, strengthens bones and more. In women who have periods or menstruate, called premenopausal women, the ovaries make most of the body’s estrogen. Hormone levels are usually high. With age, the ovaries slow down, making less estrogen. This "in-between" time, called perimenopause, happens several years before menopause. Gradually, over time, periods become irregular and then stop altogether, a time in life known as menopause. Postmenopause is when you have no periods for 12 months in a row.
After menopause, the ovaries no longer make estradiol, the most active estrogen. But your body still makes estrone, an estrogen created by converting the male sex hormone androstenedione from the adrenal glands, fat cells and elsewere. An enzyme known as aromatase converts that hormone to estrogen. This is why anti-estrogen hormonal therapy with aromatase inhibitors helps postmenopausal women.
All cells have receptors so they can respond to hormonal changes. Breast cancer cells have receptors, too.
Estrogen sends signals that control cell pathways. Hormone receptors on the surface of breast cancer cells work like satellite dishes. They detect and bring in hormone signals. These signals can direct cancer cells to grow, multiply and repair damage.
Breast cancer cells all have receptors, but not all of them have receptors for estrogen. When breast cells have estrogen receptors, the breast cancer is called estrogen receptor-positive, or ER-positive, and estrogen helps the cancer to grow. When progesterone receptors are found, the cancer is called progesterone receptor-positive, or PR-positive, and progesterone helps the cancer to grow. Your doctor may refer to the cancer as hormone receptor-positive or hormone-sensitive.
About two-thirds of breast cancers are hormone receptor-positive. They may be both ER- and PR-positive, ER-positive only, or PR-positive only. Even if the cancer has only one type of receptor, or tests just slightly positive, studies show hormonal therapy can protect you from having cancer return, or recur.
Depending on the type of hormonal therapy used to treat hormone receptor-positive breast cancer, it may
- block estrogen receptors
- reduce the amount of estrogen made in the body
- lessen the number of hormone receptors
After you were diagnosed with breast cancer, you should have had a number of tests to help your doctors learn more about the cancer and how to treat it. You can find your test results in a document called your pathology report.
The test uses ink to stain the hormone receptors in a sample of tumor tissue. Cells that have the receptors will turn the color of the ink. This test is called an immunohistochemical staining assay or immunohistochemistry (IHC) test. The results show
- If estrogen receptors are found, the breast cancer grows in response to the hormone estrogen. It is called estrogen receptor-positive, or ER-positive.
- If progesterone receptors are found, the breast cancer grows in response to the hormone progesterone. It is called progesterone receptor-positive or PR-positive.
- If both estrogen and progesterone receptors are found, the breast cancer is both ER- and PR-positive.
It is possible to have breast cancer that is both HER2-positive and hormone receptor-positive. Cancer that grows because of estrogen and progesterone and the protein HER2 is sometimes known as triple-positive breast cancer.
If you have triple-positive breast cancer, your treatment will likely include medicines that target both HER2 and hormone receptors.
Hormonal therapy, also called endocrine or anti-estrogen therapy, only works in hormone receptor-positive cancers. It reduces or blocks the estrogen and progesterone that the cancer relies on to grow and survive. This treatment disrupts the signals sent by the hormone receptors to cells.
Depending on the type, hormonal therapy may block estrogen receptors, reduce the amount of estrogen made in the body, or lessen the number of hormone receptors. It can lower the risk of the disease recurring (coming back), prevent new breast cancers and improve survival.
The main types of hormonal therapy are:
- Selective estrogen-receptor response modulators (SERMs). SERMs work by blocking the effects of estrogen on cancer cells so it can’t tell the cancer to grow. Tamoxifen is the standard hormonal therapy for premenopausal women. Common side effects include hot flashes and vaginal discharge, dryness or irritation. Rare serious side effects include stroke and a slight increased risk of blood clots and endometrial (uterine) cancer.
- Aromatase inhibitors (AIs) prevent the body from making any estrogen or progesterone. In general, AIs are given to postmenopausal women. But they may be used in premenopausal women who have breast cancer with a high risk for recurrence, along with medicines that suppress the ovaries. Side effects may include bone thinning, osteoporosis, bone fractures and problems with blood cholesterol. Aromatase inhibitors cause joint pain and muscle aches in many women who take them. They have less risk of blood clots and stroke than tamoxifen.
The most common side effects of SERMs and aromatase inhibitors are hot flashes, fatigue, difficulty sleeping, night sweats and vaginal dryness.
- Ovarian suppression or ablation uses medicine to stop premenopausal women’s ovaries from making estrogen.
- Oophorectomy, or surgery to remove the ovaries, is another way some premenopausal women can greatly lower the amount of estrogen in the body.
Before taking hormonal therapy, discuss any history of medical conditions with your doctor. Be sure you talk about any medicines or supplements you are taking as well as the risks, benefits and side effects of each type of therapy in order to make the best treatment decision for you.
During the course of your diagnosis you may hear the term triple-positive breast cancer. While that is not an official diagnosis, doctors and others sometimes use the term to describe breast cancer that tests positive for three receptors: the estrogen receptor, progesterone receptor and another receptor, called HER2.
Knowing your HER2 status is important because there are treatments designed especially for HER2-positive breast cancers. If you have triple-positive breast cancer, your treatment will likely include medicines that target the HER2 receptors and medicines that target the hormone receptors