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.
There are many different hormones that control the body’s functions. Three hormones are often referred to as “sex hormones” because they are involved in sexual development and reproduction. These hormones are:
Estrogen has multiples roles in women. It helps sex organs develop, makes pregnancy possible and strengthens bones. In women who have periods or menstruate, the ovaries make most of the body’s estrogen. Hormone levels are usually high. With age, the ovaries slow down, making less estrogen. Gradually, over time, periods become irregular and then stop altogether, a time in life known as menopause.
After menopause, the ovaries no longer make estradiol, the most active estrogen hormone. But smaller amounts of estrogen are still made elsewhere in the body. The adrenal glands, which sit on top of the kidneys, are involved in a process that converts the hormone androgen into estrogen. Fat cells and other body parts also do so as well.
The hormone progesterone, which is produced by the ovaries and helps regulate the menstrual cycle, also tapers off with the coming of menopause.
There are receptors on the surface of cells that work like satellite dishes. They detect incoming signals from the body’s hormones that direct cells to grow, multiply and repair damage.
Breast cancer cells all have receptors, but not all of them have receptors for estrogen. If estrogen receptors are found when your pathologist looks at your tumor samples, the breast cancer is called estrogen receptor-positive, or ER-positive. When progesterone receptors are found on breast cancer cells, the cancer is called progesterone receptor-positive or PR-positive.
About 75 percent of breast cancers are hormone receptor-positive, also known as hormone-sensitive. 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.
One of those tests checked your hormone receptor status, where your doctors search for the presence or absence of estrogen and progesterone receptors. Receptors are molecules that live inside or on the surface of a cell. These molecules bind to a specific substance in the body to cause an effect in the cell.
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. About 75 percent of all breast cancers are 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. About 65 percent of ER-positive breast cancers are also PR-positive
- About 30 percent of hormone-positive breast cancers are ER-positive but PR-negative.
- Between 3 and 5 percent of hormone-positive breast cancers are PR-positive and ER-negative.
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 growth-promoting 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 HR-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, or lessen the number of hormone receptors. It can reduce 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 stimulate 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 about 50 percent of 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