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Hormone Therapy for Breast Cancer: What Is It and Who Needs It?

By November 10, 2022November 29th, 2022No Comments

Hormones are vital chemical messengers in the human body. Without them, our bodies would not function normally and might fall into dysfunction and illness.

However, did you know that hormones can also be the cause of some diseases, like breast cancer?

Hormone therapy for breast cancer is what you need to stop, treat, and even prevent the development of these diseases.

RELATED: 5 Facts & Myths About Female Testosterone Replacement Therapy

 

Understanding Hormone Therapy for Breast Cancer

What Is Hormone Therapy for Breast Cancer?

Hormone therapy for breast cancer involves altering the activities and amounts of the estrogen hormone in the female body to treat breast cancer.

Hormone therapy for breast cancer should not be mistaken for menopausal hormone therapy (also known as hormone replacement therapy or HRT), which uses estrogen alone or in conjunction with progesterone to treat menopausal symptoms.

It is impossible to simultaneously prescribe menopausal hormone therapy and hormone therapy for breast cancer. Usually, a woman must stop menopausal treatment after receiving a breast cancer diagnosis and being prescribed hormone therapy for the disease.

 

How Does Hormone Therapy for Breast Cancer Work?

Blocking Estrogen Activities on Cancer Cells

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The first mechanism by which hormone therapy helps treat breast cancer is that it blocks the receptors on the cancer cells from attaching to estrogen.

A receptor is a protein that can be activated when it’s attached to estrogen. If a cancer cell receptor and estrogen are bound, the activated receptor can cause changes in some genes, allowing estrogen to be the “fuel” that drives cancer growth.

Because hormone therapy inhibits the receptors enabling the activities between the cancer cells and estrogen, only women with cancer cells that have receptors (hormone receptor-positive cancer) should consider hormone therapy for breast cancer.

That said, about 2 out of 3 breast cancers (67–80%) are hormone receptor-positive. In contrast, women whose tumors don’t have hormone receptors (hormone receptor-negative cancer) cannot benefit from the therapy and should choose other treatments.

How an estrogen molecule is attached to an estrogen receptor of a cancer cell. Source: Cancer Research UK.

How an estrogen molecule is attached to an estrogen receptor of a cancer cell. Source: Cancer Research UK

 

Reducing the Body’s Production of Estrogen

Another mechanism is lowering the amount of estrogen produced by the female body to the point that estrogen cannot fuel breast cancer development.

As mentioned above, estrogen can promote the growth of breast cancer (hormone receptor-positive cancer). In healthy breast tissues, estrogen is involved in the development and function of normal cells. Unfortunately, if normal cells are turned cancerous for some reason, estrogen can cause cancer cells to multiply and spread.

RELATED: The Impact of Hormone Replacement Therapy on Menopause Symptoms

 

Types of Hormone Therapy for Breast Cancer

Doctor-examines-mammogram-snapshot-of-breast-of-female-patient-on-the-monitors-Types-of-Hormone-Therapy-for-Breast-Cancer

Medications That Block Estrogen Activities on Cancer Cells

Medications Types Indications Duration and side effects
Tamoxifen (Nolvadex) Selective estrogen receptor modulator (SERM; anti-estrogen in breast cells, pro-estrogen in other cells) Mainly for pre-menopausal women with early-stage breast cancer

Lower the risk of developing breast cancer

Lower the risk of cancer coming back

Slow or stop the growth of the cancer

Oral. Taken either after or before surgery

5 to 10 years

Hot flashes

Vaginal dryness or discharge

Changes in the menstrual cycle

Toremifene (Fareston) Selective estrogen receptor modulator (SERM) Used less often than Tamoxifen

Only approved to treat post-menopausal women with metastatic breast cancer

Oral. Not likely to work if Tamoxifen has already been used and has stopped working

5 years (long-term use is usually not recommended)

Side effects are similar to Tamoxifen

Fulvestrant (Faslodex) Selective estrogen receptor degrader (SERD; attach to and break down estrogen receptors; anti-estrogen throughout the body) Mainly for post-menopausal women with advanced breast cancer

Given alone to treat advanced breast cancer that has/has not been treated with other hormone therapy

Injectable. Twice in the first month, 2 weeks apart, then once a month.

As long as it keeps breast cancer under control

Hot flashes

Night sweats

Headache

Mild nausea

Bone pain

Injection site pain

 

Medications That Reduce the Body’s Production of Estrogen

Medications Types Indications Duration and side effects
Letrozole (Femara)

Anastrozole (Arimidex)

Exemestane

(Aromasin)

Aromatase inhibitors (AIs; stop most estrogen production by blocking the aromatase enzyme) Mainly for post-menopausal women with treated early-stage breast cancer

Lower the estrogen level

Slow the growth of the cancer cells

Prevent cancer from coming back

Oral. Taken once a day

2 to 5 years

Hot flashes

Vaginal dryness

Bone and joint pain

Muscle pain

 

Medications That Shut Down the Ovaries (Ovarian Suppression)

Medications Types Indications Duration and side effects
Goserelin (Zoladex)

Leuprolide (Lupron)

Luteinizing hormone-releasing hormone (LHRH) agonists (stop the signals sent to the ovaries to produce estrogen) For pre-menopausal women

Stop the ovaries from producing estrogen. The ovaries should start working again after therapy discontinuation

Injectable. Given alone or with other hormone medications (Tamoxifen, Fulvestrant, aromatase inhibitors)

5 to 10 years

Symptoms of menopause (temporary): hot flashes, night sweats, vaginal dryness, and mood swings

 

When Should You Take Hormone Therapy for Breast Cancer?

After Breast Cancer Surgery (Adjuvant Therapy)

You can take hormone therapy for breast cancer after surgery to help reduce the risk of breast cancer recurrence.

Research shows that women who get at least five years of adjuvant therapy after surgery for early-stage breast cancer have lower risks of breast cancer recurrence and can live longer, up to 15 years.

 

Before Breast Cancer Surgery (Neoadjuvant Therapy)

Hormone therapy for breast cancer can also shrink a tumor before surgery, increasing the chance that surgery can entirely remove the cancer.

A shrinking tumor means you may only have a less complicated operation. Hormone therapy may also be necessary when surgery needs to be delayed or chemotherapy, which also helps shrink the tumor, is unavailable.

RELATED: Key Points of the North American Association Society (NAMS) Position Statement on Hormone Replacement Therapy (HRT) for Women

 

Can Hormone Therapy Prevent Breast Cancer From Occurring?

Yes. Most breast cancers are hormone receptor-positive, and trials have demonstrated the use of hormone therapy in preventing breast cancer in women with higher risks.

According to research:

  • Tamoxifen lowers the risk of breast cancer by about 50% in post-menopausal women for at least 20 years.
  • Some aromatase inhibitors reduce the risk of breast cancer by 50-65% in post-menopausal women for 3-7 years.

 

Depending on your condition, you may undergo multiple tests to keep track of your health and look for cancer progression or recurrence while receiving hormone therapy for breast cancer. Your doctor may adjust your treatment based on the results of these tests to determine how you respond to the treatment.

 

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