Hormone Therapy for Breast Cancer

Approximately two out of three breast cancers are hormone receptor positive, according to the American Cancer Society. This means that the breast cancer cells have receptors for either estrogen or progesterone, which are hormones that enable the growth of cancer.

Hormone therapy, also called endocrine therapy, prevents the hormones from binding to these receptors. Hormone therapy only works on cancers that are hormone receptor positive. This isn’t the same hormone therapy that’s given for menopause.

In this article, you’ll read more about hormone therapy, including how and when it’s used to treat breast cancer. You’ll also learn about the side effects and risks, and what to expect.

Every person’s experience is different, so it’s best to talk with your healthcare provider if you have specific questions about your breast cancer treatment.

This article will discuss the different types of hormone therapy, when it's used, what to expect, and the side effects and risks to this type of treatment.

When Is Hormone Therapy Used?

Hormone therapy is used when tumors are hormone receptor positive. It can be done at any cancer stage, but is typically done after surgery to reduce the risk of the cancer returning. This makes it adjuvant treatment.

Although sometimes it can be used before surgery to help shrink the tumor, it’s generally prescribed post-surgery.

It can also be prescribed for people whose cancers have returned or metastasized (spread to other parts of the body).

Types of Hormone Therapy Treatment

Different kinds of hormone therapy treat breast cancer, including treatments that block:

• Ovarian function
• Estrogen production
• Effects of estrogen

Blocking Ovarian Function

The ovaries are the main sources of estrogen production. Blocking or suppressing ovarian function can reduce or get rid of all estrogen production.

This can be done via ovarian ablation, surgery (removal of the ovaries), or radiation. These are typically performed in premenopausal women and are permanent procedures.

Ovary function can also be temporarily suppressed with drugs known as gonadotropin-releasing hormone (GnRH) agonists or luteinizing hormone-releasing hormone (LHRH) agonists. These drugs block the signals that tell the ovaries to make estrogen.

Examples of these drugs include:

• Zoladex (goserelin)
• Lupron (leuprolide)

Blocking Estrogen Production

Drugs called aromatase inhibitors are used mainly in postmenopausal women. They have not been well studied in men with breast cancer. They block aromatase, which is an enzyme that’s used to make estrogen.

Premenopausal women make too much aromatase to inhibit, so these are only given to premenopausal women if they’re also taking drugs to suppress ovarian function.

Aromatase inhibitors include:

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

Blocking the Effects of Estrogen

Different kinds of drugs are used to block the effects of estrogen.

Selective estrogen receptor modulators (SERMs) block the effects of estrogen in breast tissue. SERMs mimic estrogen and attach to the estrogen receptors, preventing estrogen from binding to receptors.

Examples of SERMs include:

• Nolvadex (tamoxifen)
• Fareston (toremifene)

Another drug that blocks the effects of estrogen is Faslodex (fulvestrant). The difference is that, unlike SERMs, Faslodex doesn’t mimic estrogen.

Side Effects and Risks

Like many medications and treatments, there can be side effects and risks to hormone therapy. These side effects depend on the specific drug used and the type of hormone therapy.

Your healthcare provider will discuss all of the potential side effects, benefits, and risks with you, taking into consideration your cancer type and your personal and family health history.

Ovarian Suppression

Three common side effects of ovarian suppression are:

• Bone loss
• Mood swings or changes
• Loss of libido

Blocking Estrogen Production

Aromatase inhibitors are used to block estrogen production. Side effects of aromatase inhibitors can include:

• Risk of heart attack, heart failure, and high cholesterol (hypercholesterolemia)
• Bone loss
• Joint pain
• Mood changes, depression

Each drug can have its own specific side effects. Talk with your healthcare provider about the side effects of the specific drug prescribed to you. It’s also worth noting that not everyone will have the same side effects to each drug.

Blocking Estrogen’s Effects

Selective estrogen receptor modulators block estrogen’s effects, especially in the breast tissue.

Side effects of SERMs can include:

• Increased risk of endometrial cancer
• Hot flashes
• Atrophic vaginitis
• Blood clots and pulmonary embolism
• Increased risk of stroke
• Increased risk of cataracts

Talk with your healthcare provider about whether these drugs are right for you. They can discuss the potential risks along with the benefits, given your medical situation.

What to Expect

Hormone therapy is typically a daily pill taken orally, although it may be a monthly shot if you’re on Faslodex.

You’ll still see your treatment team regularly for follow-up visits. If you’re experiencing any side effects or unusual symptoms, tell your healthcare provider. They can often help with side effects or offer tips to minimize them. They’ll also monitor your cancer for any changes or recurrence.

Summary

Hormone therapy for breast cancer is much different than general hormone therapy for menopause. Everyone’s treatment journey is unique, and you may or may not be on this as part of your treatment plan.

Your healthcare provider will discuss which hormone therapy is best for you. Ask them about any potential risks or side effects, as well as any potential adverse reactions to medications you may be taking.

A Word From VeryWell

Receiving a cancer diagnosis can feel overwhelming. It’s natural to be apprehensive about starting cancer treatment, especially if you’re unfamiliar with it.

Talk with your healthcare provider about your concerns regarding any of these medications, especially if you’re worried about the permanent effects to estrogen production or if you’re premenopausal.