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How is hormone therapy used in breast cancer?

By Ashley McClure-Wolfson, PharmD, BCACP, AAHIVP May 05, 2023 • 7 min

If you’ve been prescribed hormone therapy for breast cancer treatment or prevention, you probably have a lot of questions. This article will help answer some FAQs about what hormone therapy is, how it can help you, common side effects and how long you might take it.

What is hormone therapy?

Before we talk about hormone therapy, it’s important to understand how hormones work. Hormones are chemical messengers made in the body that travel through your blood to different cells and tissues. Estrogen and progesterone are hormones produced in the ovaries in premenopausal women. In all women, other tissues can also make these hormones (like fat cells and the skin). Some types of breast cancer (called hormone receptor-positive, or simply HR-positive) use estrogen and/or progesterone to grow. About 67% to 80% of breast cancers in women are HR-positive.

Hormone therapy is used in HR-positive breast cancer to either stop the body from making these hormones or change how these hormones work with the cancer cells.

There are two main types of hormone therapy:

  • Aromatase inhibitors (includes anastrozole, exemestane and letrozole)
  • Selective estrogen receptor modulators, or SERMs (namely tamoxifen)

These medications are typically given as tablets that are taken by mouth once daily.

How can hormone therapy help me? 

Hormone therapy can be used as treatment in early breast cancer or in advanced breast cancer. It can also be used to prevent breast cancer in women who are at high risk.

Advanced breast cancer:

  • Hormone therapy can be used if the cancer has come back after treatment or has spread to other parts of the body. Your hormone therapy can slow the growth of the tumor or may shrink it for a period of time. You might take your hormone therapy alone or in combination with targeted therapy, a different type of anticancer medication.

Early breast cancer:

  • Hormone therapy is sometimes used after surgery (called adjuvant therapy) or before surgery (called neoadjuvant therapy).
  • Adjuvant hormone therapy can reduce the risk of the breast cancer coming back and can help you live a longer, cancer-free life.
  • Neoadjuvant hormone therapy can reduce the size of the tumor before surgery.

Prevention of breast cancer:

  • Hormone therapy can lower the chances of developing breast cancer in women who are at increased risk. That means that if you have a higher risk of developing breast cancer, you may be able to lower your chances of getting it by taking hormone therapy. 

What are the common side effects?

As with any medication, it’s important to talk openly with your care team, including your pharmacist. Talk about your concerns and any side effects you may be experiencing. They can give you tips to help you manage these side effects at home.

Common side effects of anastrozole, exemestane and letrozole include:

  • Bone pain
  • Feeling tired
  • Headache
  • Hot flashes
  • Joint pain, stiffness or swelling
  • Muscle pains
  • Nausea
  • Vaginal dryness

Common side effects of tamoxifen include:

  • Changes to the menstrual cycle (if premenopausal)
  • Headache
  • Mood changes
  • Nausea
  • Hot flashes
  • Feeling tired
  • Joint pain, stiffness or swelling
  • Muscle pains
  • Vaginal discharge or dryness

These are not all the possible side effects of hormone therapy. For more information, talk with your pharmacist or your cancer care team. 

How long will I need to take hormone therapy? 

One of the most common questions women ask is, “How long will I need to take my hormone therapy?” It’s also one of the most important questions. Hormone therapy not only treats breast cancer, but it can also prevent it from coming back or from developing in the first place. But it only works if you take it. Your healthcare provider will tell you how long you can expect to take your hormone therapy. It’s important to keep taking your hormone therapy every day as prescribed until your provider tells you to stop.

Your individual treatment plan may be different, but the following guidelines are recommended for most women:

Advanced breast cancer:

  • It’s common for women with advanced breast cancer to take hormone therapy for many years. You’ll have regular checkups with your healthcare provider. During these visits, they will monitor how well you are responding to treatment. Your provider may talk with you about changing your medication if the cancer isn’t responding to it or if you are experiencing side effects. At that time, you may decide to switch to a different hormone therapy. Your provider can help answer any questions or concerns you may have about your individual treatment plan.

Early breast cancer:

  • If you’re taking adjuvant hormone therapy (after surgery), then you’ll likely be taking it for five to 10 years. This will help lower the risk of the cancer coming back and can also reduce the risk of dying from breast cancer.

Breast cancer prevention:

  • You can plan on taking your hormone therapy for at least five years. Some women may benefit from taking it for 10 years or more, depending on their individual risk factors.

No matter where you are on your cancer journey, your Walgreens pharmacist is here to help. 

Published May 2023.