Hormonal therapy blocks the effects of oestrogen on breast cancer cells and reduces the risk of breast cancer coming back.
Hormones help control how cells grow and what they do in the body. The hormones oestrogen and progesterone, particularly oestrogen, can encourage some breast cancers to grow.
Hormonal therapies reduce the amount of oestrogen in the body or stop it attaching to the cancer cells. They only work for women with oestrogen-receptor (ER) positive cancers.
Your cancer doctor will advise you to take hormonal therapy to reduce the risk of the breast cancer coming back. It also helps reduce the risk of getting a new breast cancer in your other breast. Sometimes hormonal therapy drugs are given before surgery to shrink a cancer and avoid a mastectomy.
You usually take hormonal therapy drugs for a number of years. For some women, this could be up to 10 years. You usually start taking them after surgery or chemotherapy.
The type of hormonal therapy you have depends on:
- whether you have been through the menopause or not
- the risk of the cancer coming back
- how the side effects are likely to affect you.
Hormonal therapy drugs reduce the risk of breast cancer coming back. It is important to take it for as long as you have been prescribed it for. Try to make taking it part of your daily routine so it becomes a habit.
Most women cope well with the side effects of hormonal therapy. They may be more of a problem in the first few months, but usually get better over time. If the side effects do not improve or are difficult to cope with, talk to your specialist nurse or cancer doctor. They can prescribe drugs to help and suggest ways of coping.
If you are still having problems after this, then your cancer doctor may suggest changing to a different type of hormonal therapy.
Tamoxifen is an anti-oestrogen drug that stops oestrogen attaching to breast cancer cells and making them grow.
Tamoxifen is taken daily as a tablet.
It is usually given to women who have not been through the menopause. Some women take it for a few years and then take another type of hormonal therapy drug called an aromatase inhibitor.
Your cancer doctor may advise you to take tamoxifen for 5 to 10 years. If you are close to menopause when you start taking it, your doctor may change you to an aromatase inhibitor after a few years of taking tamoxifen. They may do blood tests to check your hormone levels first.
There may be situations where continuing with tamoxifen may not be suitable. If any side effects of tamoxifen become a problem, you may need to take a different hormonal therapy.
Aromatase inhibitors (AIs)
Aromatase inhibitors (AIs) are the main hormonal therapy used for women who have been through the menopause. They stop oestrogen being made in the fatty tissue.
AIs may also be given to younger women with drugs to stop the ovaries working, or after the ovaries have been removed (see below).
These drugs are taken daily as a tablet. Side effects can include:
- joint and muscle pain
- hot flushes
Your bone health
If taken over a long period of time, AIs can cause bone thinning (osteoporosis). Before you start an AI, you have a scan called a DEXA (dual-energy x-ray absorptiometry) scan, to check your bone health (density).
If you are at risk of osteoporosis, your cancer doctor may prescribe drugs called bisphosphonates to protect your bones. Some women may already be taking bisphosphonates to reduce the risk of breast cancer spreading to the bones.
Your doctor may advise you to take calcium and vitamin D supplements to help strengthen your bones. There are things you can do to look after your bones including eating healthily and doing regular exercise such as walking.
If you have not been through the menopause, your cancer doctor may advise having one of these treatments with another hormonal therapy:
This stops the ovaries making oestrogen and causes a temporary menopause.
This removes the ovaries and causes a permanent menopause.
These treatments lower oestrogen levels, which reduces the risk of breast cancer coming back. But they can also affect your bone health. Before treatment starts, you have a DEXA scan to check your bone health (density).
Your doctor will advise you on how to look after your bones.
Drugs to stop the ovaries making oestrogen (ovarian suppression)
Goserelin (Zoladex®) is a drug that stops the ovaries making oestrogen and causes a temporary menopause. You may have goserelin on its own or with tamoxifen or an AI.
Your specialist nurse will give you goserelin as a monthly injection under the skin of the tummy (abdomen).
Removing the ovaries (ovarian ablation)
This may be an option for women who do not want to take goserelin injections. You will usually have tamoxifen or an AI as well as ovarian ablation.
Removing the ovaries involves a small operation. It can often be done during a short stay in hospital using keyhole surgery. The surgeon makes a small cut in the tummy area and inserts a thin tube with a tiny light and camera on the end (laparoscope).
The surgeon removes the ovaries through the cut using the laparoscope, which has a small surgical instrument attached to it. Women usually recover quickly from this operation.
If you have this surgery, your periods will stop straight away and you will have your menopause. It also means you will no longer be able to have children. Becoming infertile because of cancer treatment can be hard to cope with, but there is support available.
Below is a sample of the sources used in our breast cancer information. If you would like more information about the sources we use, please contact us at email@example.com
European Society for Medical Oncology. Primary breast cancer: ESMO clinical practice guidelines for diagnosis, treatment and follow-up. Annals of oncology 26 (supplement 5): v8–v30. 2015.
Morrow M, et al. Chapter 79: malignant tumors of the breast. DeVita, Hellman and Rosenberg’s cancer: principals and practice of oncology (10th edition). Lippincott Williams and Wilkins. 2014.
National Institute for Health and Care Excellence (NICE). Early and locally advanced breast cancer: diagnosis and management. July 2018.
Scottish Intercollegiate Guidelines Network. SIGN 134. Treatment of primary breast cancer: a national clinical guideline. September 2013.
This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr Rebecca Roylance, Consultant Medical Oncologist.
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