What is Hormone Therapy for Breast Cancer?
Hormone therapy is another form of systemic therapy. It is designed to either lower the level of oestrogen in your body or to stop the oestrogen from stimulating the cancer cells.
Your doctor will recommend this treatment if your tumour is hormone-sensitive, i.e. oestrogen receptor (ER) or progesterone receptor (PR) positive.
Why Consider Hormone Therapy for Breast Cancer?
Hormonal therapies used to treat breast cancer are not the same as hormone replacement therapy (HRT) used to manage the symptoms of menopause.
Role of hormonal therapy in breast cancer
- Reduces the size of the tumour before surgery (as neoadjuvant treatment)
- Prevents the recurrence of cancer, after surgical resection
- Delays or completely stops the growth of cancer cells
There are different hormone therapies for women who are perimenopausal and those who are post-menopausal due to the different levels of oestrogen produced throughout these stages.
All hormonal therapies can cause menopausal symptoms. These include hot flushes, vaginal dryness, reduced libido (sex drive) and mood changes. The severity of these symptoms varies between women and between different treatments. These side effects often improve after treatment stops. Some women feel no symptoms at all.
Types of Hormonal Therapy
Anti-oestrogens work by stopping oestrogen in the body from attaching to cancer cells. One of the most well-known anti-oestrogens is tamoxifen. Tamoxifen can be used to treat women of any age, regardless of whether they have reached menopause. Tamoxifen is taken as a single tablet every day, usually for 5 years. However, in some cases, we may advise treatment for up to 10 years.
Additional rare side effects include increased risk of blood clots, such as deep vein thrombosis (DVT) or pulmonary thrombosis (PE), stroke and uterine cancers.
Aromatase inhibitors (AIs) work by blocking oestrogen production but only work for post-menopausal women. Examples of aromatase inhibitors include anastrozole (Arimidex®), letrozole (Femara®) and exemestane (Aromasin®).
Aromatase inhibitors are not suitable for women who:
- Have not yet reached menopause
- Are in the middle of menopause
- Have temporarily stopped having menstrual periods because of chemotherapy
Aromatase inhibitors are taken as a single tablet every day, usually for 5 years. Once again, it can be taken for up to 10 years. If you are being treated with an AI, you may be referred to check your vitamin D level and bone mineral density (BMD) tests to monitor your bone mineral density levels, particularly if you are at risk of developing osteoporosis.
Side effects of aromatase inhibitors include stiffness and pain in bones or joints (arthralgia) and increase the risk of osteoporosis, which may increase the risk of bone fractures.
Ovarian suppression works by stopping the ovaries from making oestrogen. Drugs like goserelin (Zoladex®), given as a monthly injection, stop the ovaries from making oestrogen temporarily. They only work while the woman is taking the drug.
Drugs that stop the ovaries from working also cause menopause, but this usually only lasts while taking the drugs. However, the effects of these drugs may be permanent if a woman is close to her natural menopause when she starts treatment.
Oestrogen production can be stopped permanently by removing the ovaries surgically (oophorectomy) or giving radiotherapy to the ovaries. Ovarian treatments are only suitable for women who have not yet reached menopause.
Surgery to remove the ovaries or radiotherapy to the ovaries causes permanent menopause. Women who have these treatments can no longer have children naturally.
Progestins are artificial forms of the female hormone progesterone. They are sometimes used for women with secondary breast cancer. The most common progestins are megestrol acetate (Megace®) and medroxyprogesterone (Provera®). Progestins are given as a tablet.
Progestins may cause nausea and also increase appetite, which can lead to weight gain. Other possible side effects include muscle cramps and slight vaginal bleeding (spotting).
Everyone is different in how they respond to treatment. If you experience significant side effects with your hormonal therapy, feel free to talk to your GP or oncologists, you may be able to take a different dose or different brand or different medicine.
Do not let side effects stop you from getting the benefits of hormonal therapy.