Estrogen receptor-positive (ER-positive) breast cancer is the most common type of breast cancer diagnosed today. According to the , about 2 out of every 3 cases of breast cancer are hormone receptor-positive. Most of these cases are ER-positive, meaning that there are estrogen receptors on the surface of the cell that bind to estrogen.

If your doctor suspects breast cancer, you will likely have a biopsy. A doctor will test your cells to see if they are cancerous. If there is cancer, your doctor will also test the cells for characteristics that include what receptors, if any, are present on the surface of the cancer cells. The outcome of this testing is important when making treatment decisions. What treatment options are available is highly dependent on the test results.

If you have ER-positive breast cancer, your cancer cells grow in the presence of the hormone estrogen. Estrogen occurs naturally in the body. Drugs that interfere with estrogen’s ability to promote cancer cell growth are used to treat ER-positive breast cancers.

ER-positive breast cancers have the most favorable outlook of all subtypes, according to a study in . ER-positive cancer typically responds to hormone therapy. Even with a relapse, this type has more treatment options than ER-negative tumors. Some declines in women’s breast cancer mortality rates can be attributed to the effectiveness of hormone therapy drugs prescribed for women with ER-positive breast cancer.

In breast cancer, hormone receptors are the proteins located in and around breast cells. These receptors signal cells — both healthy and cancerous — to grow. In the case of breast cancer, the hormone receptors tell the cancer cells to grow uncontrollably, and a tumor results.

Hormone receptors can interact with estrogen or progesterone. Estrogen receptors are the most common. This is why ER-positive is the most common form of breast cancer. Some people are diagnosed with progesterone receptor-positive (PR-positive) breast cancer. The key difference is whether cancerous cells are getting growth signals from estrogen or progesterone.

Testing for hormone receptors is important in treating breast cancer. In some cases, there are no hormone receptors present, so hormone therapy isn’t a good treatment option. This is called hormone receptor-negative breast cancer. However, according to , about 2 out of 3 people with breast cancer have some form of hormone receptors present. This makes them candidates for hormone therapy.

Your outlook depends on the stage of your cancer when it’s discovered. Cancer is staged numerically. Each number reflects different characteristics of your breast cancer. These include the size of the tumor and whether cancer has moved into lymph nodes or distant organs. But the cancer subtype doesn’t play a role in staging, only in treatment decisions.

Survival statistics of women with the major subtypes of breast cancer — such as ER-positive, HER2-positive, and triple-negative — are grouped together. With treatment, most women with very early stage breast cancers of any subtype can expect a normal life span.

Survival rates are based on how many people are still alive years after they were first diagnosed. Five-year and 10-year survival are commonly reported.

According to the , 5-year survival rates are:

  • stage 0: 100 percent
  • stage 1: 100 percent
  • stage 2: 93 percent
  • stage 3: 72 percent
  • stage 4 (the metastatic stage): 22 percent

One thing to note is that these statistics also included women with the more aggressive HER2-positive and triple-negative cancers. And it takes 5 years to get to a 5-year statistical survival rate, so newer therapies are not included in these numbers. It’s likely that a woman with ER-positive breast cancer diagnosed today may have a higher chance of survival.

All women who have ER-positive breast cancer will be recommended a type of hormone therapy. This type of therapy aims to prevent estrogen from activating cancer cell growth.

In the past, premenopausal women were treated with a selective estrogen receptor modulator like tamoxifen. Postmenopausal women were treated with an aromatase inhibitor like Arimidex. Both treatments starve the cancer cells of estrogen so they can’t grow.

More recent studies found that premenopausal women had better outcomes when they were given medication to stop ovarian production of estrogen, or if they had their ovaries removed. A woman enters menopause when her ovaries stop producing estrogen. Then they are treated with aromatase inhibitors like women who enter menopause naturally.

Most women with early stage breast cancer will have surgery before starting hormone therapy. Surgical options will vary depending on the size of the breast, patient preference, and the size of the cancer. A lumpectomy removes breast tissue but not the entire breast. A mastectomy removes the entire breast. Most women will likely also have one or more lymph nodes removed from under the arm. Depending on what type of surgery you have you may also need radiation.

In cases of early stage ER-positive cancer, you can ask your doctor if an Oncotype DX test is needed. This test will examine 21 genes in cancerous tumors that can help identify whether your risk of relapse is high. The test can also show whether chemotherapy will be beneficial and reduce your risk of relapse.

If you have a low recurrence score you will likely not need chemotherapy. If you have a high recurrence score you will likely need chemotherapy, surgery, and hormone therapy. The Oncotype DX test, which may be paid for by Medicare and most insurance plans, is recommended for women who:

  • have early stage ER-positive node positive or node negative breast cancer
  • have HER 2-negative breast cancer

Advanced cancer, or stage 4 cancer, means that the tumor has already metastasized and started to grow in another organ. In cases of breast cancer this usually occurs in the bones, liver, lungs, or brain.

Stage 4 is the most advanced stage of breast cancer. But it’s uncommon to have stage 4 ER-positive breast cancer at the time of the initial diagnosis. Although at this point the cancer is incurable, a woman with stage 4 ER-positive breast cancer may respond well to hormone therapies that can extend life for many years.

ER-positive breast cancer has a high chance of being successfully treated, especially when it’s discovered early. A diagnosis at a later stage will have a less positive outlook, but being diagnosed at a later stage is less common. And there are still many treatment options for late stage cancer.

The outlook for women with ER-positive breast cancer is generally good and there are effective treatments. The chances for a long life are excellent.