Hormone Receptor-Positive Breast Cancer

August 31, 2015

Hormone receptorinfo-icon-positive, or HR-positive, breast cancer grows in response to the hormones estrogeninfo-icon and progesteroneinfo-icon. These hormones occur naturally in the body and prompt cellinfo-icon action in our system in different ways.

If your doctor recommends hormonal therapyinfo-icon 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 factorinfo-icon in breast cancer. Or that hormone replacement therapyinfo-icon, or HRT, is used to treat symptoms of menopauseinfo-icon 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 receptorinfo-icon (ERinfo-icon), progesterone receptorinfo-icon (PRinfo-icon), 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.


Role of Hormones in the Body

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 menopauseinfo-icon.

After menopause, the ovaries no longer make estradiolinfo-icon, 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 cycleinfo-icon, also tapers off with the coming of menopause.

How Estrogen Makes Some Cancers Grow

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 estrogeninfo-icon. If estrogen receptors are found when your pathologistinfo-icon looks at your tumorinfo-icon samples, the breast cancer is called estrogen receptor-positiveinfo-icon, or ER-info-iconpositive. When progesteroneinfo-icon receptors are found on breast cancer cells, the cancer is called progesterone receptor-positiveinfo-icon or PR-info-iconpositive.

About 75 percent of breast cancers are hormone receptorinfo-icon-positive, also known as hormoneinfo-icon-sensitive. They may be both ERinfo-icon- and PR-positive, ER-positive only, or PR-positive only. Even if the cancer has only one type of receptorinfo-icon, or tests just slightly positive, studies show hormonal therapyinfo-icon 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

How Do We Test for Hormone Receptor-Positive Breast Cancer?

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 receptorinfo-icon status, where your doctors search for the presence or absence of estrogeninfo-icon and progesteroneinfo-icon receptors. Receptors are molecules that live inside or on the surface of a cellinfo-icon. These molecules bind to a specific substance in the body to cause an effect in the cell.

The test uses ink to stain the hormoneinfo-icon receptors in a sample of tumorinfo-icon tissueinfo-icon. Cells that have the receptors will turn the color of the ink. This test is called an immunohistochemical staining assayinfo-icon or immunohistochemistryinfo-icon (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-positiveinfo-icon, or ER-info-iconpositive. 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-positiveinfo-icon or PR-info-iconpositive.
  • If both estrogen and progesterone receptors are found, the breast cancer is both ERinfo-icon- 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 proteininfo-icon 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.

If none of these receptors are found, the cancer is called triple-negative.

For more information on a hormone receptor-positive breast cancer diagnosisinfo-icon, go to our section on Testing.


Treatments for HR-positive breast cancer may include surgeryinfo-icon, radiation therapyinfo-icon, chemotherapyinfo-icon, targeted therapyinfo-icon (if you also have HER2-positive disease) or hormonal therapyinfo-icon.

Hormonal therapy, also called endocrineinfo-icon or anti-estrogeninfo-icon therapyinfo-icon, only works in HR-positive cancers. It reduces or blocks the estrogen and progesteroneinfo-icon that the cancer relies on to grow and survive. This treatment disrupts the signals sent by the hormoneinfo-icon 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.

It is important to note that hormonal therapy is not the same as hormone replacement therapyinfo-icon (HRT), which is sometimes given after menopauseinfo-icon to replace hormones no longer made by the ovaries.

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 premenopausalinfo-icon women. Common side effects include hot flashes and vaginal dischargeinfo-icon, 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 postmenopausalinfo-icon women. But they may be used in premenopausal women who have breast cancer with a high risk for recurrenceinfo-icon, along with medicines that suppress the ovaries. Side effects may include bone thinning, osteoporosisinfo-icon, bone fractures and problems with blood cholesterol. Aromatase inhibitors cause joint paininfo-icon and muscle aches in about 50 percent of women who take them. They have less risk of blood clots and stroke than tamoxifeninfo-icon.

The most common side effects of SERMs and aromatase inhibitors are hot flashes, fatigueinfo-icon, difficulty sleeping, night sweats and vaginal dryness.

  • Ovarian suppressioninfo-icon or ablationinfo-icon uses medicineinfo-icon to stop premenopausal women’s ovaries from making estrogen.
  • Oophorectomyinfo-icon, 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.

Get more information about hormonal therapy in our section on Treatments and Research.

Triple-Positive Breast Cancer

During the course of your diagnosisinfo-icon 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 receptorinfo-icon, progesterone receptorinfo-icon and another receptorinfo-icon, 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 hormoneinfo-icon receptors