Some breast cancers develop due to a problem involving hormones, including estrogen and progesterone. These hormones play a role in telling breast cells to grow.

In hormone receptor-positive breast cancer, the receptors for hormones cause breast cells to grow in an uncontrolled way.

Two types of hormone receptor-positive breast cancer are estrogen receptor-positive (ER-positive) breast cancer and progesterone receptor-positive (PR-positive) breast cancer.

In these cancers, the cancer cells receive their growth signals from estrogen and progesterone, respectively.

When the growth of cancer cells results from problems with both types of receptor, it is simply called hormone receptor-positive breast cancer. When hormones are not involved, it is called hormone receptor-negative breast cancer.

This article focuses on ER-positive breast cancer, including its risk factors, symptoms, diagnosis, and treatment.

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Experts believe that hormone receptor-positive cancers account for two-thirds of breast cancer cases.

In ER-positive breast cancer, cancerous cells receive their growth signals from the hormone estrogen.

Estrogen receptors are the most common type of hormone receptor on breast cells. For this reason, ER-positive breast cancer is more common than other types of breast cancer.

In fact, two-thirds of breast cancer cases are hormone receptor-positive, according to the American Cancer Society.

A number of risk factors may increase a person's risk of developing ER-positive breast cancer. We will cover these in more detail below.

Sex: Females are far more likely than males to develop any type of breast cancer, but males can have it. When they do, 90% of cases will be hormone receptor-positive. Males with health conditions that lead to higher levels of estrogen in the body have a higher risk.

Age: Hormone receptor-positive breast cancer becomes more likely with age.

Lifetime exposure: Females who start menstruating early, reach menopause late, and never have children may have a higher risk, as they have a longer lifetime exposure to estrogen and progesterone.

Hormone treatment: The National Cancer Institute note that using hormone treatment — such as to relieve the symptoms of menopause — may increase the risk of this type of cancer. Females whose mothers took a hormone treatment called diethylstilbestrol during pregnancy between 1940 and 1971 may also have a higher risk.

Other factors: Other factors that may increase the risk include excessive alcohol consumption, a high body mass index (BMI) in early life, obesity after menopause, and a lack of physical activity. These may all increase exposure to breast cancer related hormones.

Factors that may lower a person's risk of this type of cancer include breastfeeding, as this may reduce exposure to estrogen.

Click here to learn more about male breast cancer.

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A person with ER-positive breast cancer may experience pain in the breast or nipple.

The symptoms of ER-positive breast cancer are similar to those of many other types of breast cancer. The most common symptom is a lump.

Other symptoms can include:

  • skin irritation or dimpling
  • discharge from the nipple
  • breast swelling
  • pain in the breast or nipple
  • redness or thickness of the nipple or breast skin
  • a change in breast shape

A lump is a common symptom of breast cancer, but not all breast cancers involve a lump. What other signs should people look out for? Learn more here.

If a person finds a lump or other breast changes, or if these appear during routine screening, a doctor may suggest an ultrasound to gather more information.

If breast cancer is a possibility, the doctor will usually recommend a biopsy.

A biopsy can confirm:

  • whether or not cancer is present
  • if it is present, which type of cancer it is
  • whether or not hormone receptors play a role

During a biopsy, a medical professional will remove a small amount of breast tissue for examination. Sometimes, a surgeon will remove the tumor and send the tissue they have removed to the laboratory for analysis.

Another option is immunohistochemistry testing. This procedure uses a tissue sample to identify estrogen and progesterone receptors in cancer cells.

The results will help a doctor determine the best treatment option.

What happens during a breast biopsy? Learn more here.

Treatment for ER-positive breast cancer aims to reduce estrogen levels in the body or stop estrogen from encouraging the growth of cancerous breast cells.

The choice of treatment will depend on many factors, including:

  • the stage of the cancer
  • if it has spread, how far
  • the type of breast cancer

If the cancer is ER- or PR-positive, a doctor will probably recommend hormone therapy as part of the treatment plan.

If there is no sign of hormonal involvement, the cancer will be hormone receptor-negative. It will not respond to hormone treatment, so the doctor will suggest another approach for treatment.

Types of hormone treatment

Several hormone therapy options are available. We list them in more detail below.

Luteinizing hormone-releasing hormone agonist

A luteinizing hormone-releasing hormone (LHRH) agonist can "turn off" the production of estrogen in the ovaries. As a result, less estrogen is available to support the growth of ER-positive breast cancer.

This treatment is most common among females with early stage ER-positive breast cancer who have not yet reached menopause. A doctor may combine LHRH with another option, such as tamoxifen.

Examples of LHRH agonists include:

  • goserelin acetate (Zoladex)
  • leuprolide (Lupron)
  • triptorelin pamoate (Trelstar)

Using these drugs can trigger temporary symptoms of menopause, such as:

  • hot flashes
  • vaginal dryness
  • mood swings

Aromatase inhibitors

Aromatase inhibitors block an enzyme called aromatase. Aromatase converts the hormone androgen into estrogen. Blocking aromatase reduces the amount of estrogen available for the body to use.

This means that there is less estrogen available to encourage ER-positive breast cancer cells to grow.

Aromatase inhibitors only work in females who have already gone through menopause. These drugs target the adrenal gland and fat tissue where the body makes estrogen, but they do not prevent the ovaries from producing estrogen. After menopause, females receive much less estrogen from their ovaries than they did before menopause.

Common examples of aromatase inhibitors include:

  • anastrozole (Arimidex)
  • exemestane (Aromasin)
  • letrozole (Femara)

Side effects include muscle pain and pain or stiffness in the joints. In the long term, there may also be a higher risk of osteoporosis.

Selective estrogen receptor response modulators

Selective estrogen receptor response modulators (SERMs) act as blockers on the breast cells. They attach to the estrogen receptors in breast cells. In this way, they stop estrogen from sending the signal to the cell to grow.

Examples of SERMs include:

  • tamoxifen (Nolvadex, Soltamox)
  • toremifene (Fareston), for people with advanced ER-positive breast cancer after menopause

A doctor may prescribe one of these drugs alongside another option.

Possible adverse effects include:

  • mood swings
  • hot flashes
  • vaginal dryness or discharge

Taking additional medication may help reduce these effects.

Much less commonly, there may be a higher risk of uterine cancer, blood clots, deep vein thrombosis, pulmonary embolism, and stroke.

Estrogen receptor downregulators

Estrogen receptor downregulators (ERDs) also block the effects of estrogen.

ERDs change the shape of estrogen receptors so that they do not work as well. They also reduce the number of estrogen receptors on the breast cells, so that there will be less room for estrogen to attach to receptors.

One examples of an ERD is fulvestrant (Faslodex). A doctor may prescribe this:

  • for advanced ER-positive breast cancer in postmenopausal females
  • if other hormone therapy medicines — such as tamoxifen — are not working

Possible adverse effects include:

  • hot flashes
  • headaches
  • nausea
  • bone pain
  • pain at the site of the injection

Prolonged use of these drugs can increase the risk of osteoporosis.

Preventive surgery

Before menopause, a doctor may suggest surgery to remove the ovaries. Undergoing this procedure can lower estrogen levels in the body and may help prevent a recurrence of breast cancer.

However, this is an invasive treatment that can have a considerable impact on a person's life. They will no longer be able to bear children, for example.

The individual will make this decision with their doctor after talking through all the considerations.

Early detection through screening

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The earlier a doctor can diagnose ER-positive breast cancer, the better the survival rate.

Current guidelines from the American College of Physicians suggest asking a doctor about screening from the age of 40 years. People with an average risk of breast cancer should undergo screening every 2 years from the age of 50–74.

Other organizations, including the American Cancer Society, have different recommendations — namely, that females ages 45–54 should undergo annual screenings.

Each person's situation is different, however, and a doctor may recommend a different plan for a person with a higher risk.

The outlook for people with ER-positive breast cancer tends to be good, especially when a doctor has made an early diagnosis.

A person who receives a diagnosis of any type of breast cancer in the early stages has a 99% chance of surviving for at least another 5 years, and often longer. However, if the cancer spreads to other organs, there is a 27% chance of surviving at least 5 more years.

Knowing the signs, seeking help if symptoms appear, undergoing screening as recommended, and getting suitable treatment if necessary are all ways to increase the chance of a full recovery from breast cancer.

Q:

I have been using the pill as birth control for several years. Will this increase my risk of breast cancer?

A:

Studies looking into the link between taking birth control pills and the risk of breast cancer have consistently shown that the risk of breast and cervical cancers increased in women who use oral contraceptives.

For breast cancer specifically, studies have shown that women who had ever used oral contraceptives had a slight (7%) increase in the relative risk of breast cancer compared with women who had never used oral contraceptives.

The longer a woman uses oral contraceptives, the greater the risk of breast cancer seems to be.

However, this may depend on the hormone formulation, as there are many different types and combinations of hormones in these contraceptives. The risk seems to decline after women stop taking the pill. In one study, this was evident by 10 years following cessation.

Christina Chun, MPH Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.