Breast Cancer and Hormone Therapy

There are many different types of breast cancer. Many breast cancer tumors—around 70% to 80%—have receptors for hormones like estrogen and progesterone. These receptors bind to their respective hormones, helping the tumor to grow. Because of this, hormonal therapies are often used to combat these types of tumors. Hormone therapy uses drugs to slow or prevent the growth of hormone-sensitive tumors by either blocking the body’s ability to produce a specific hormone (typically estrogen) or by interfering with its effects on breast cancer cells.

Benefits of Hormone Therapy

Hormone therapies have proven to be highly effective in the treatment of hormone-sensitive breast cancers. By targeting hormones that fuel cancer growth, these therapies can significantly increase survival and reduce the chance of cancer returning after initial treatment. Hormone therapy generally has fewer side effects than chemotherapy, and because it targets specific hormonal pathways, it is welcomed as a less aggressive treatment option for many patients.

How Hormone Therapy Is Used in Breast Cancer Treatment

Hormonal therapies are used in all stages of breast cancer treatment, from prevention in high-risk individuals to treatment of metastatic breast cancer.

• Adjuvant therapy for early-stage cancers: Hormone therapies are often prescribed after surgery to remove early-stage breast cancers.
• Neoadjuvant therapy: In some cases, hormone therapies are used to shrink tumors before surgery.
• Treatment for recurrent, advanced, or metastatic breast cancer: Estrogen-blocking drugs can be used independently or in conjunction with targeted therapies—drugs that target attack proteins on breast cancer cells.
• Breast cancer prevention in high-risk individuals: Drugs that block estrogen production and drugs that block estrogen’s effects have been shown to reduce high-risk patients’ chances of developing breast cancer.

Types of Hormone Therapy Used for Breast Cancer

Different hormone therapies take various approaches to cutting off a tumor’s supply of estrogen.

Preventing Hormone Production in the Ovaries

Because the ovaries are the primary source of estrogen in premenopausal women, doctors sometimes target ovarian function as a way to fight cancer in these women. Ovarian ablation is permanent blockage of ovarian function; this can be done by surgically removing the ovaries or by targeting them with radiation. Alternatively, drugs known as gonadotropin-releasing hormone (GnRH) agonists, temporarily suppress ovarian function by interfering with signals that stimulate the ovaries to produce estrogen. All of these therapies can induce menopausal symptoms such as hot flashes, night sweats, and vaginal dryness.

Blocking Estrogen Production

Estrogen also exists in the bodies of postmenopausal women, men, and others without ovarian function. Aromatase is an enzyme responsible for producing estrogen in fat cells. Aromatase inhibitors prevent this action, making them useful for patients with hormone-sensitive breast cancers. They are also sometimes used in conjunction with ovarian suppression or ablation in premenopausal women. Common side effects of aromatase inhibitors include hot flashes, vaginal dryness, and pain in bones, joints and muscles.

Blocking Estrogen Receptors

Other types of drugs prevent tumor cells from using estrogen to fuel their growth. These include two classes of drugs known as selective estrogen receptor modulators (SERMs) and selective estrogen receptor degraders (SERDs). Both types of drugs bind to estrogen receptors in breast tumors, taking the place of the estrogen a tumor needs to grow.

SERMs have anti-estrogen effects in breast cells but act like estrogen in other parts of the body, such as the uterus and bones. SERDs, on the other hand, have anti-estrogen effects throughout the body. Additionally, SERDs bind more tightly to estrogen receptors and cause them to break down. SERDs are most often prescribed to post-menopausal women, but they are also used in men and in pre-menopausal women in combination with ovarian suppression.

Commonly Used SERMs

Tamoxifen is a SERM commonly used to treat pre-menopausal, post-menopausal, and male breast cancer patients. It’s used in all stages of breast cancer treatment, including prevention in high-risk patients, as adjuvant and neoadjuvant therapies, and for treatment of breast cancers that have spread to other parts of the body. Toremifene is another SERM, which is used to treat metastatic breast cancer in post-menopausal women.

Common side effects of tamoxifen and toremifene include hot flashes, menstrual cycle changes, and vaginal dryness or discharge. Among patients whose breast cancer has spread to the bones, a small number of patients experience short-term growth in bone tumors, leading to bone pain. This condition usually subsides quickly.

Commonly Used SERDs

Fulvestrant is often used to treat advanced and metastatic breast cancers. Unlike the SERMs described above, which are taken as pills, fulvestrant is given in two-injection doses. Typically, the first two doses are given two weeks apart, and subsequent doses are given monthly.

Elacestrant is another SERD that’s prescribed in specific circumstances. Taken as a pill, it’s used to treat advanced hormone-sensitive, HER2-negative breast cancer with ESR-1 gene mutation when the tumor has grown after another type of hormone treatment. Common side effects of SERDs include hot flashes, fatigue, appetite loss, nausea, headache, and muscle, bone, or joint pain.

Radiologic imaging plays a crucial role in the diagnosis and ongoing management of breast cancer, including during hormone therapy. Imaging is vital for monitoring the cancer’s response to therapeutic interventions. Regular imaging is often necessary to assess progress and to detect any signs of recurrence as early as possible. Iowa Radiology’s skilled and caring providers are here for you every step of the way. We’re always happy to answer any questions you have, and we’ll do our best to keep you as comfortable as possible during exams.

Learn more about imaging at Iowa Radiology, or subscribe to our blog for up-to-date information about important health topics.

Resources

American Cancer Society. Hormone Therapy for Breast Cancer. Cancer.org. Updated January 31, 2023. Accessed September 12, 2024. https://www.cancer.org/cancer/types/breast-cancer/treatment/hormone-therapy-for-breast-cancer.html

American Cancer Society. Hormone Therapy for Breast Cancer in Men. Cancer.org. Updated January 31, 2023. Accessed September 12, 2024. https://www.cancer.org/cancer/types/breast-cancer-in-men/treating/hormone-therapy.html

National Cancer Institute. Hormone Therapy for Breast Cancer. Cancer.gov. Updated July 12, 2022. Accessed September 12, 2024. https://www.cancer.gov/types/breast/breast-hormone-therapy-fact-sheet#what-types-of-hormone-therapy-are-used-for-breast-cancer.