New Health Guide

ER Positive Breast Cancer

Oct 11, 2013

Not all types of breast cancer are the same. Some types (60%) have cancer cells that are ER positive (ER+), which means that they have estrogen receptors. These estrogen-receptor-positive cancer cells have protein molecules, which bind to estrogen to encourage their growth and proliferation. How to treat ER positive breast cancer? What do other results from hormone receptor test mean?

Treatments for ER Positive Breast Cancer

There are various ways to treat ER positive breast cancer:

1. Selective Estrogen-receptor Tesponse Modulators

Referred to as SERMs, these drugs block the harmful effects of excess estrogen in breast cells by binding to your receptors. The most common SERM used for ER+ breast cancer is Tamoxifen. Fareston (toremifene) is also used for advanced cases among postmenopausal women. Raloxifene is another SERM that has been used to prevent breast cancer in women who have a high risk of developing estrogen-positive breast cancer.

2. Aromatase Inhibitors

These drugs stop estrogen production in women who are postmenopausal. They block the effects of aromatase enzyme, which converts another hormone called androgen into estrogen in small amounts. This results in less estrogen becoming available to induce growth and proliferation of ER-positive cancer cells. These medications work only with postmenopausal women, since they do not affect estrogen produced from the ovaries of younger women. Estrogen in postmenopausal women comes from their fat tissues and their adrenal glands. Examples of aromatase inhibitors are Arimidex (anastrozole), Femara (letrozole), and Aromasin (exemestane).

3. Estrogen-receptor Downregulators

Also called ERDs, these drugs block estrogen effects in your breast by occupying estrogen receptors, preventing estrogen molecules from binding to them. ERDs also affect the number and shape of the receptors so that they do not work well. One example is Faslodex (fulvestrant), which is used in the treatment of advanced, estrogen positive breast cancer among postmenopausal women.

4. Luteinizing Hormone-releasing Hormone Agents

LHRHs shut off ovarian function and stop the production of estrogen, which results in less estrogen being available to support growth of ER+ breast cancer. These are usually injected once every month for several months. These are often given to premenopausal women who have early-stage breast cancer. When stopped, your ovaries begin functioning normally after some time. Examples include Lupron (leuprolide), Zoladex (goserelin), and Trelstar (Triptorelin).

Below is a general discussion of ER positive breast cancer and breast cancer in general:

What do Hormone Receptor Test Results Mean?

Most testing laboratories use a special staining procedure, which detects estrogen receptors in breast cancer cells. This test, called immunohistochemical staining, is used in various ways by different labs, so they analyze and report the results in various ways.

Your doctor will tell you after your tests which category best describes your breast cancer type. Most types of breast cancer are estrogen-receptor-positive.

Test Results



Breast cancer cells are positive for estrogen receptors. This occurs in 80% of patients.


Breast cancer cells are positive for estrogen receptors and are also positive for progesterone receptors. Both hormones support the growth of the breast cancer. This occurs in 65% of patients.


Breast cancer cells are positive for estrogen receptors but are negative for progesterone receptors. This occurs in 13% of patients.


Breast cancer cells are negative for estrogen receptors and but are positive for progesterone receptors. This means that progesterone is more likely to support growth of cancer cells. This occurs in 2% of patients.


Breast cancer cells are negative for receptors for both hormones. This is also known as “hormone-receptor-negative”, which occurs in 25% of patients.


A positive test result for either or both types of hormone receptors means that your breast cancer is “hormone-receptor-positive.” In these cases, hormonal therapy can help slow down or stop breast cancer cell growth by reducing estrogen levels or by blocking estrogen effects. These medications may also help reduce the risk of cancer recurrence or cancer coming back after treatment.

If tests come out positive, your doctor may prescribe hormonal therapy to be included in your plan of treatment. If breast cancer is hormone receptor-negative, hormonal therapy is unlikely to be recommended. Other effective treatments, however, are available.