Hormone Therapy in Breast Cancer
A breast cancer diagnosis involves many decisions about treatment, and understanding why certain therapies are recommended can help you feel more informed and prepared.
For people with hormone receptor-positive breast cancer, hormone therapy (also called endocrine therapy) is an important part of treatment. Unlike chemotherapy, which targets rapidly dividing cancer cells, hormone therapy works by blocking or reducing the effects of hormones that can encourage certain breast cancers to grow.
Hormone therapy is often prescribed after surgery and may be used alongside other treatments such as radiation therapy or chemotherapy. It is commonly taken for 5–10 years to reduce the risk of breast cancer recurrence.
While hormone therapy is highly effective, the long duration of treatment means some people experience ongoing side effects that can affect everyday activities, exercise tolerance, physical function, and quality of life. Understanding how these medications work and how to manage their effects is an important part of breast cancer rehabilitation.
What Are Hormone Receptors in Breast Cancer?
To understand hormone therapy, it helps to understand hormone receptor status. Some breast cancer cells have proteins called hormone receptors that attach to hormones circulating in the body. These hormones can act like signals that stimulate cancer cells to grow.
The two main hormone receptors tested in breast cancer are:
Oestrogen receptors (ER)
Oestrogen receptor-positive (ER-positive) breast cancers have receptors that allow oestrogen to promote cancer cell growth.
Progesterone receptors (PR)
Progesterone receptor-positive (PR-positive) breast cancers have receptors that respond to progesterone.
Breast cancer that is ER-positive and/or PR-positive is considered hormone receptor-positive (HR-positive). Approximately 70–80% of breast cancers are hormone receptor-positive, meaning hormone therapy is often recommended as part of treatment.
How Does Hormone Therapy Work?
Hormone therapy does not work by removing hormones completely. Instead, it reduces the ability of cancer cells to use hormones as growth signals. There are several types of hormone therapy used in breast cancer treatment, and they work in different ways. Some medications reduce the amount of oestrogen produced by the body, while others block oestrogen from acting on breast cancer cells.
Ovarian suppression may also be used to reduce oestrogen production in premenopausal women. By reducing or blocking these hormonal signals, hormone therapy can help slow or prevent the growth of breast cancer cells and reduce the risk of the cancer returning.
The medication recommended depends on factors including:
- Whether you are premenopausal or postmenopausal
- Your age
- Your cancer characteristics
- Your risk of recurrence
- Previous treatments received
- Your overall health
Types of Hormone Therapy
The main categories of hormone therapy used in breast cancer treatment include:
- Selective oestrogen receptor modulators (SERMs)
- Aromatase inhibitors (AIs)
- Ovarian suppression therapy
- Selective oestrogen receptor degraders (SERDs)
1. Selective Oestrogen Receptor Modulators (SERMs)
SERMs block oestrogen from attaching to receptors on breast cancer cells, reducing the hormonal signals that can encourage cancer cells to grow. Tamoxifen is the most commonly used SERM in breast cancer treatment.
Tamoxifen can be used in:
- Premenopausal women
- Perimenopausal women
- Postmenopausal women
- Some men with hormone receptor-positive breast cancer
Treatment is commonly prescribed for 5 years, although some people may continue for longer depending on recurrence risk.
Common side effects of tamoxifen include:
- Hot flushes
- Night sweats
- Mood changes
- Fatigue
- Vaginal dryness or changes
- Reduced libido
- Menstrual changes
- Joint or muscle discomfort
Tamoxifen can also have effects on bone health. In premenopausal women, it may help maintain bone density, while in postmenopausal women it may slightly increase bone loss risk.
2. Aromatase Inhibitors (AIs)
Aromatase inhibitors reduce the amount of oestrogen produced in the body. After menopause, most oestrogen is produced through conversion of other hormones in tissues such as fat and muscle. Aromatase inhibitors block this conversion process.
Common aromatase inhibitors include:
- Anastrozole
- Letrozole
- Exemestane
These medications are mainly used in postmenopausal women, although they may also be used in younger women when combined with ovarian suppression therapy.
Common side effects of AIs include:
- Joint stiffness and pain
- Muscle aches
- Hot flushes
- Fatigue
- Reduced bone density
- Increased risk of osteoporosis
- Vaginal symptoms
- Changes in cholesterol levels
Joint pain and stiffness are among the most commonly reported side effects and can significantly affect mobility and exercise participation.
3. Ovarian Suppression Therapy
Before menopause, the ovaries are the main source of oestrogen. Ovarian suppression therapy temporarily reduces ovarian hormone production, lowering oestrogen levels.
This may be achieved through:
Medication injections
Medications called gonadotropin-releasing hormone (GnRH) agonists temporarily switch off ovarian function.
Examples include:
- Goserelin (Zoladex)
- Leuprorelin
Surgical removal of the ovaries
Some people may undergo:
- Bilateral oophorectomy (removal of both ovaries)
Why is ovarian suppression used?
It may be recommended for people with higher-risk hormone receptor-positive breast cancer, particularly younger women.
Ovarian suppression may be combined with:
- Tamoxifen
- Aromatase inhibitors
4. Selective Oestrogen Receptor Degraders (SERDs)
SERDs work differently from tamoxifen by attaching to oestrogen receptors and causing them to break down. The most established example is Fulvestrant (Faslodex). Fulvestrant is usually given as an injection and is commonly used for advanced or metastatic hormone receptor-positive breast cancer. Newer oral SERDs are also being investigated and introduced into treatment pathways.
Common Side Effects of Hormone Therapy and How to Manage Them
Hormone therapy causes changes to the body’s hormonal environment, which can lead to symptoms similar to menopause.
Hot flushes and night sweats: Caused by reduced oestrogen levels and may affect sleep. Strategies include exercise, stress management, breathable clothing, and discussing treatment options with your healthcare team.
Joint pain and stiffness: Common with aromatase inhibitors and may cause aching, reduced mobility, and difficulty with activities. Exercise, including resistance, aerobic, and flexibility training, can help manage symptoms.
Fatigue: May be related to hormonal changes, sleep disruption, reduced activity, stress, or other treatments. Exercise rehabilitation can improve energy, physical capacity, and quality of life.
Bone health changes: Lower oestrogen levels can increase the risk of osteopenia, osteoporosis, and fractures. Weight-bearing exercise, resistance training, adequate calcium and vitamin D, and bone monitoring can support bone health.
Weight and body composition changes: Hormone therapy may affect weight, muscle mass, and fitness. Strength training helps maintain muscle, metabolism, independence, and confidence.
Menopausal and sexual health symptoms: May include vaginal dryness, reduced libido, discomfort, and emotional changes. Support and management options are available through your healthcare team.
Hormone Therapy FAQs
Hormone therapy can raise a number of questions, particularly around side effects, treatment duration and managing physical changes. Below are some frequently asked questions about hormone therapy after breast cancer.
Q: Why is hormone therapy used after surgery?
A: Even after surgery removes the visible tumour, microscopic cancer cells may remain.
Hormone therapy helps by:
- Reducing the chance of recurrence
- Lowering the risk of cancer returning in the breast
- Reducing the risk of cancer spreading to other areas of the body
- Improving long-term survival outcomes
For many people with hormone receptor-positive breast cancer, hormone therapy is one of the most important treatments for reducing recurrence risk.
Q: How long is hormone therapy taken?
A: Hormone therapy is usually prescribed for 5 years as a minimum, sometimes extended to 7–10 years.
The recommended duration depends on:
- Cancer stage
- Tumour characteristics
- Lymph node involvement
- Age
- Menopausal status
- Individual recurrence risk
Q: Can I stop taking hormone therapy because of the side effects?
A: It is important not to stop hormone therapy without discussing it with your oncology team.
Side effects can be challenging, but there are often strategies to improve symptoms, including:
- Adjusting medications
- Switching hormone therapy types
- Managing specific symptoms
- Adding supportive therapies
Speak with your oncologist or cancer care team if you develop new, persistent or worsening side effects that are affecting your daily activities, sleep, mood or ability to exercise. Your healthcare team can help identify strategies to manage side effects and determine whether any changes to your treatment are appropriate.
Q: Can hormone therapy affect my risk of osteoporosis?
A: Some types of hormone therapy can contribute to bone loss and reduced bone mineral density, particularly aromatase inhibitors and ovarian suppression treatments that lower oestrogen levels. Your healthcare team may monitor your bone health and recommend strategies such as weight-bearing and resistance exercise, adequate calcium and vitamin D intake, and other treatments where appropriate.
Q: What type of exercise is recommended during hormone therapy?
A: There isn’t one specific type of exercise that is suitable for everyone taking hormone therapy. A combination of aerobic exercise, resistance training and mobility or flexibility exercises can help maintain strength, fitness, bone health and physical function. A physiotherapist can help develop an individualised exercise program based on your symptoms, treatment history, current fitness and goals, and can modify exercises if joint pain, fatigue, reduced mobility or other treatment-related changes are affecting your ability to exercise. Exercise can also be gradually progressed as your strength and tolerance improve.
How Hunter Rehab Hub Can Help
At Hunter Rehab Hub, we can help you manage the physical changes associated with hormone therapy for breast cancer including education and guidance, individualised exercise prescription, and conservative treatment strategies to help manage treatment-related side effects and maintain physical function.
Your physiotherapist will work with you to develop a safe and achievable management plan that considers your treatment history, current symptoms, physical capacity and individual goals.
We can also support the management of other treatment-related concerns, including lymphoedema, reduced shoulder or upper-limb movement, pain, fatigue, and physical changes following breast cancer surgery or radiation therapy.
Our goal is to help you maintain strength, mobility and physical function, while supporting your ability to remain active and participate in the activities that are important to you during and after breast cancer treatment.
Contact Us
Looking for support with managing the physical changes and side effects associated with hormone therapy? Contact Hunter Rehab Hub to discuss how physiotherapy can support you in managing symptoms, maintaining strength, mobility and physical function throughout your breast cancer treatment.
References
Cancer Australia. (n.d.). Hormonal therapies. Australian Government. Cancer Australia – Hormonal therapies
Cancer Australia. (n.d.). Managing physical changes due to breast cancer. Australian Government. Cancer Australia – Managing physical changes due to breast cancer
Cancer Council Australia. (n.d.). Hormone therapy for breast cancer. Cancer Council Australia – Hormone therapy for breast cancer
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Disclaimer
This content is general in nature and provided for educational purposes only. It is not a substitute for individualised advice, diagnosis, or treatment. If you have concerns about your symptoms or health, consult a qualified healthcare professional.
