Some breast cancers are stimulated by the hormone oestrogen. This means that oestrogen in the body ‘helps’ the cancer to grow. This type of breast cancer is called oestrogen receptor positive (ER+).
Hormone therapy, also called endocrine therapy, is a treatment that blocks the effect of oestrogen on breast cancer cells. Different hormone therapy drugs do this in different ways.
Hormone therapy will only be prescribed if your breast cancer is oestrogen receptor positive. It may be given:
- to reduce the risk of breast cancer coming back after surgery
- to reduce the size of your cancer before surgery to remove it
- to treat breast cancer that has already come back or spread
All breast cancers are tested for oestrogen receptors using tissue from a biopsy or after surgery. If your cancer is ER+, your specialist will discuss with you which hormone therapy they think is most appropriate.
Tests may also be done for progesterone (another hormone) receptors. The benefits of hormone therapy are less clear for people whose breast cancer is only progesterone receptor positive (PR+ and ER-). Very few breast cancers fall into this category. However, if this is the case for you your specialist will discuss whether hormone therapy is appropriate.
If hormone receptors are not found, then hormone therapy will not be of any benefit.
Hormone therapy is usually started after surgery (known as adjuvant treatment), to reduce the risk of the breast cancer coming back. It may also reduce the risk of a new primary breast cancer developing.
If you’re having radiotherapy after surgery but not chemotherapy, hormone therapy may be started during or after the radiotherapy.
If you’re having chemotherapy after surgery, hormone therapy will usually start after chemotherapy has finished.
If you’re having trastuzumab (Herceptin), hormone therapy may be given at the same time.
Sometimes, hormone therapy may be given before surgery (known as primary or neo-adjuvant treatment) to reduce the size of the cancer. Occasionally, hormone therapy is given when surgery isn’t an option – for example for people who have other illnesses such as lung or heart conditions.
If cancer has come back or spread
Hormone therapy is used to treat ER+ breast cancer that has come back (recurrence) or that has spread to another part of the body (secondary breast cancer). It’s given either alone or alongside other treatments, depending on what treatments you had before.
If your breast cancer comes back during or after you've been treated with hormone therapy, you may be offered a different type of hormone therapy.
DCIS (ductal carcinoma in situ)
Women at moderate or high risk of breast cancer because of their family history may be offered hormone therapy to reduce their risk of developing breast cancer.
The most commonly used hormone therapy drugs used to treat breast cancer are:
- aromatase inhibitors (anastrozole, exemestane and letrozole)
- goserelin (Zoladex)
- fulvestrant (Faslodex)
If you’re prescribed tamoxifen or an aromatase inhibitor after surgery, you will be recommended to take these for at least five years. This is because they are most effective when taken for this amount of time. Some people will be recommended to continue taking them for another five years.
How long other hormone drugs are given for varies from person to person.
If you are taking hormone therapy because your breast cancer has come back or spread, you will usually continue taking it for as long as it is effective.
Reducing the risk of breast cancer
Some hormone therapy drugs are used to try and reduce the risk of breast cancer in women who have not had breast cancer. These include:
These drugs may be given to women who are at moderate or high risk of breast cancer and are usually taken for five years.
Like any treatment, hormone therapy can cause side effects. Everyone reacts differently to drugs and some people have more side effects than others. These side effects can often be managed and those described here will not affect everyone.
Some side effects can be experienced with all hormone therapies, while others are specific to certain drugs. You can read about specific side effects on our individual drug pages (listed above).
If you’re concerned about any side effects, regardless of whether they are listed here, talk to your specialist team as soon as possible.
Common side effects
The most common side effects of hormone therapy are menopausal symptoms, such as:
- hot flushes
- night sweats
- vaginal dryness
- reduced libido (sex drive)
- mood changes
These symptoms are often more intense than when the menopause happens naturally.
Other common side effects with most hormone drugs include:
- joint/muscle pain and stiffness
- effects on the bones
- tiredness or fatigue (extreme tiredness)
Managing side effects
Many people find the side effects of hormone therapy drugs difficult to cope with.
If side effects are putting you off taking your hormone therapy, it’s important to talk with your cancer specialist before making any decisions to stop it. There may be ways to improve your symptoms or your cancer specialist may suggest that you change to a different drug.
If you have persistent side effects from hormone therapy, tell your specialist team so that they can decide how best to manage them.
You may also find the following web pages useful:
- menopausal symptoms
- complementary therapies
- will hormone therapy affect my diet?
- physical activity during and after treatment