Types of breast cancer hormone therapy | Cancer Research UK
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Types of breast cancer hormone therapy

The female hormones oestrogen and progesterone can trigger the growth of some breast cancer cells. So some drugs or treatments are used to lower the levels of oestrogen and progesterone or block their effects. You may have hormone therapy before or after surgery, or to treat breast cancer that has come back. Some older women may be offered hormone therapy if they cannot have surgery due to other medical conditions or if they don't want surgery.

It is most common to have hormone therapy after surgery. Hormone treatment has been proven to reduce the risk of oestrogen receptor positive breast cancer coming back. You usually take it for at least 5 years.

If  your breast cancer cells don't have oestrogen receptors, hormone therapy is unlikely to work. Your specialist may then suggest that you have chemotherapy after surgery instead.

Types of hormone therapy

There are three main types of hormone therapy. These are

  • Aromatase inhibitors, such as anastrozole (Arimidex), exemestane (Aromasin) and letrozole (Femara)
  • A drug called tamoxifen
  • Stopping the ovaries from working with either surgery or luteinising hormone (LH) blockers such as goserelin (Zoladex)

Each type of hormone therapy works in a slightly different way. Which one is best for you depends mainly on whether or not you have had your menopause.


CR PDF Icon You can view and print the quick guides for all the pages in the treating breast cancer section.



What hormone therapy is

Hormones are substances made naturally in the body, where they control the growth and activity of normal cells. The ovaries produce the female hormones oestrogen and progesterone before the menopause. After the menopause oestrogen is made in body fat. Oestrogen can stimulate the growth of some breast cancer cells. So hormone treatments for breast cancer lower the levels of oestrogen and progesterone in the body, or block their effects.

Hormone therapy is only likely to work if the breast cancer cells have oestrogen receptors (ER). If your cancer cells don't have these receptors, your specialist may suggest that you have chemotherapy rather than hormone therapy. There is information about hormone receptors in this section.

You may have hormone therapy to treat breast cancer in the following situations


Hormone therapy before surgery

You may have hormone therapy to shrink a large or locally advanced cancer in the breast before surgery. This treatment only helps women with oestrogen receptor positive breast cancer. It aims to shrink the cancer down so that you can have just the cancer removed (lumpectomy or wide local excision), instead of needing the whole breast removed (a mastectomy). 

While you take the hormone therapy before surgery, doctors monitor the cancer to see if it shrinks. Recent research shows that aromatase inhibitors can work better than tamoxifen at shrinking breast cancers before surgery. But aromatase inhibitors have different side effects to tamoxifen. So your doctor will take your individual situation into account when deciding which treatment may suit you best.


Hormone therapy after surgery

The most common time to have hormone therapy for breast cancer is after surgery. If you are also having chemotherapy you usually start the hormone therapy after the chemotherapy ends. 

Hormone therapy has been proven to lower the risk of breast cancer coming back. You usually have the treatment for at least 5 years. But exactly how long depends on the particular treatment you are having. 

One advantage of hormone treatments is that hormones are very safe. Although side effects can occasionally be troublesome, they are rarely serious.


If you can't have surgery

Surgery is the main treatment for breast cancer but some women over 70 years of age have health problems that mean they can't have surgery. Some women don't want to have surgery. In this situation, if your cancer is oestrogen receptor positive your doctor may recommend treatment with hormone therapy such as tamoxifen, anastrozole or letrozole. Doctors call this primary endocrine therapy. 

The treatment will not get rid of the breast cancer but can stop it from growing and shrink it. This treatment can often control the cancer for more than 18 months or 2 years. After this time, if the cancer starts growing again, your doctors may change to a different type of treatment.


If the cancer has come back or spread

Hormone therapy can control or shrink a breast cancer that has spread to other parts of the body. It may keep it under control for some time but cannot get rid of it completely. There is detailed information about hormone therapy for secondary breast cancer in this section.


Types of hormone therapy

There are several types of hormone treatments used for primary breast cancer including


Aromatase inhibitors

Although women who have had their menopause don't produce oestrogen from their ovaries, a small amount is made in body fat. Aromatase inhibitors block this oestrogen from being made. So these drugs are used for women who've had their menopause. You take them as tablets once a day. There is information below about

Aromatase inhibitors for early breast cancer

Doctors can use the aromatase inhibitors anastrozole, exemestane or letrozole to treat women with early breast cancer, who have had their menopause. You have these therapies after surgery and other treatment and they aim to reduce the chance of the cancer coming back. Aromatase inhibitors can also treat breast cancer that has spread. You can find information about this in the treatment for secondary breast cancer section.

Anastrozole (Arimidex) has been tested after surgery for early breast cancer. It works as well as tamoxifen at preventing breast cancer from coming back. But it has different side effects. Anastrozole generally has fewer side effects than tamoxifen, although it is more likely to cause weakening of the bones (osteoporosis). The weakening can lead to joint pain or bone fractures. A rare side effect of anastrozole is an increase in the amount of cholesterol in the blood which can lead to heart problems. 

A trial called the Intergroup Exemestane Study (IES trial) compared tamoxifen for 2 to 3 years followed by exemestane (Aromasin), with tamoxifen only for 5 years. The results showed that switching to exemestane lowered the risk of the cancer coming back more than staying on tamoxifen. 

Another aromatase inhibitor called letrozole (Femara), has been tested and licensed for early breast cancer. You may also have letrozole before surgery to try to shrink your cancer so that you can have a smaller operation to remove it.

Your doctor will discuss with you which treatment is most suitable for you. And they will take into account the following factors

  • The side effects and benefits of each different hormone therapy
  • Whether you have already had treatment with tamoxifen
  • What they think the risk of your cancer coming back might be. 

You can find out about the side effects of each type of hormone therapy by clicking on the links above for each particular drug.

Aromatase inhibitors to prevent breast cancer

A major trial looked at anastrozole as a way of preventing breast cancer in women at high risk of the disease. This trial is called IBIS 2 and showed that anastrozole can reduce the risk of developing breast cancer by 50% in women at high risk. You can find detailed information about the IBIS 2 trial on our clinical trials database.



Tamoxifen is a hormone treatment developed over 30 years ago. It stops oestrogen from telling breast cancer cells to grow. So it lowers the risk of breast cancer coming back (recurring) after treatment. It can also help to reduce the risk of cancer in the other breast by 40%. You take tamoxifen as tablets. There is detailed information about the benefits and side effects of tamoxifen on the next page of this section.

We know from research that taking tamoxifen greatly improves survival rates of women with oestrogen receptor positive breast cancer. Doctors use tamoxifen mainly for women who have not yet had their menopause or for postmenopausal women who are at low risk of their cancer coming back or can't have an aromatase inhibitor. Recent large trials have shown that taking tamoxifen for 10 years instead of 5 years can lower the risk of the cancer coming back and increase survival even more. But taking tamoxifen for longer can also increase the risk of side effects. So your doctor will balance the benefits and the risks in your individual case when advising you on how long you need to take it for.

For some post menopausal women who are able to have an aromatase inhibitor, doctors think it may be better to have tamoxifen for 2 or 3 years and then to take an aromatase inhibitor. They suggest that this may lower the risk of developing side effects that happen when you take either tamoxifen or an aromatase inhibitor for 5 years or more. The ATAC trial showed that anastrozole was better at stopping the cancer coming back but the women taking it did not live longer. This may be because anastrozole can occasionally cause an increase in the amount of cholesterol in the blood which causes heart problems. 

We need more research into the side effects of taking aromatase inhibitors for 5 years to work out if this is a problem for all women taking aromatase inhibitors. We also need generally to find the best way of giving hormone treatment after early breast cancer. It will depend on your situation as to which hormone treatment your doctor recommends for you.

Research has shown that tamoxifen can help to prevent breast cancer from developing in women who are at high risk. The benefits of tamoxifen in preventing breast cancer seem to last for at least another 5 years after the treatment has ended. Tamoxifen is not currently licensed in the UK as a drug to prevent breast cancer. But the National Institute for Health and Care Excellence (NICE) has recommended that it should be considered as a treatment for women at high risk.

Tamoxifen impact statement


Stopping the ovaries from working

Another type of hormone treatment that can be used for premenopausal women is to stop the ovaries from working with particular drugs. Or the ovaries can be removed so that they don't produce oestrogen. These treatments are called ovarian ablation. 

If you have not yet had your menopause, and you have ER positive breast cancer, your doctor will usually offer you tamoxifen hormone therapy, and possibly chemotherapy. The chemotherapy often stops your ovaries working, but not always. If your doctor suggests chemotherapy, but you decide not to have it, they should offer ovarian ablation instead.

You can read below about ovarian ablation with

Luteinising hormone (LH) blockers

These drugs are also called LH analogues. They block a hormone produced in the pituitary gland that stimulates your ovaries to make and release oestrogen. This stops your ovaries working, so you won't have periods or release eggs while you are having the injections. But when you stop taking the drug, your ovaries should start working again. But, if you are close to the age at which your menopause would naturally start, your ovaries may not start working again after this type of treatment. So it can tip you into an early menopause.

The most commonly used LH blocker for breast cancer is goserelin (Zoladex). You have Zoladex as an injection once a month. You are likely to have menopausal symptoms, such as hot flushes and mood changes while you are having Zoladex. There is also a risk that your bones will become thinner. You should have a DEXA scan to check your bone density before you start this treatment or soon afterwards. We have information about ways of coping with menopausal symptoms.

Researchers are looking into the role of ovarian ablation and chemotherapy for premenopausal women. It may be possible to use an LH analogue to switch off the ovaries instead of using chemotherapy for women with hormone sensitive breast cancer with a low risk of coming back. There are ongoing trials to find out more about the role of ovarian ablation in treating breast cancer. There is information about these trials on our breast cancer treatment research page.

Surgery to remove the ovaries

If you don't like the idea of a monthly injection, another option (which is permanent) is to have your ovaries removed in an operation. This causes a sudden menopause and menopausal symptoms. There are ways of reducing hot flushes and sweating and you can read about them on our page on coping with menopausal symptoms.


More information about hormone therapy

Scientists and doctors are working together all the time to find new ways of using hormone therapy drugs and combinations. You can find out about current trials for breast cancer by searching our clinical trials database

You can phone the Cancer Research UK nurses on freephone 0808 800 4040. The lines are open from 9am to 5pm, Monday to Friday. They will be happy to answer any questions that you have.

You may also like to contact one of the breast cancer organisations. They often have books and leaflets, some of which are free. We also have details of breast cancer books and booklets.

There is more information in the main hormone therapy section

If you want to find people to share experiences with online, you could use Cancer Chat, our online forum. 

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Updated: 2 August 2014