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Learn what goserelin is and when this hormone therapy is used to treat breast cancer.

1. What is goserelin (Zoladex)?

Goserelin is a type of hormone (endocrine) therapy used to treat breast cancer in premenopausal women (women who have not been through the menopause). It comes as an implant that is given as an injection into the abdomen (belly).

Goserelin is the generic (non‑branded) name of the drug. Its current brand name is Zoladex.

It can also be used to try to preserve fertility during .

2. How does goserelin work as a treatment for breast cancer?

Some breast cancers use oestrogen in the body to help them grow. These are known as oestrogen-receptor positive or ER-positive breast cancers. Invasive breast cancers are tested to see if they’re ER-positive using tissue from a biopsy or after breast surgery.

Before the menopause, oestrogen is mainly produced in the ovaries. Goserelin switches off this production by interfering with hormone signals from the brain that control how the ovaries work. This is known as ovarian suppression. You may also hear it called ovarian function suppression or ovarian ablation.

Within about three weeks of the first goserelin injection, your oestrogen will be lowered to a level similar to that of a post-menopausal woman (a woman who has been through the menopause) and your periods will normally stop. This effect is generally temporary and will only last for as long as you’re having goserelin.

When you stop having the drug, your ovaries will usually start to produce oestrogen again. Most women will start their periods within three months to a year after finishing treatment. However, if you’re approaching the age of natural menopause when your treatment finishes, your ovaries may not start working again.

3. When is goserelin prescribed?

Goserelin is used to treat some people with . It may also be used to treat people with .

It’ll only be given if you are premenopausal and your breast cancer is .

Goserelin may be given on its own or is often combined with another hormone therapy such as tamoxifen or drugs known as aromatase inhibitors (anastrozole, exemestane and letrozole). Research has suggested this may reduce the risk of the breast cancer coming back for some premenopausal women who have had chemotherapy.

There may be a small extra benefit of having an aromatase inhibitor over tamoxifen but there might be different side effects to consider that can affect your quality of life. Your specialist will help you discuss the possible benefits and side effects.

Aromatase inhibitors are not used on their own as hormone therapy in premenopausal women because they’re not an effective treatment while the ovaries are still making oestrogen, but they can be given alongside goserelin. Your treatment team will discuss with you what they recommend and why.

4. Can goserelin preserve fertility during chemotherapy?

Chemotherapy can cause damage to the ovaries, reducing the number and quality of eggs and affecting a woman’s ability to become pregnant. Some studies have shown that goserelin may protect the ovaries during chemotherapy as it temporarily ‘shuts’ them down (known as ovarian suppression). However, the effectiveness of goserelin as a method of preserving fertility is still debated and further research is needed.

Goserelin cannot replace other fertility preservation methods like egg and embryo freezing and even if your periods do return after treatment, this doesn’t necessarily mean you have preserved your fertility.

If you want to try to preserve fertility during chemotherapy discuss this with your treatment team before starting treatment.

Goserelin is not suitable during pregnancy or while breastfeeding.

5. How is goserelin given?

Goserelin comes as an implant (a very small pellet) in a pre-filled syringe. It’s given as a subcutaneous injection (an injection into the fatty tissue under the skin) into your abdomen. Some people find the injection uncomfortable.

You can be prescribed a local anesthetic cream to numb the skin before the injection to reduce any discomfort. However, after the cream has been applied you’ll need to wait for at least an hour before the area is numb, so it’s important to ask about using this cream well in advance of your injection so it can be arranged in time.

For primary breast cancer, it’s recommended that goserelin is given every 28 days (four weeks). The injection is called a ‘depot injection’, which means that the drug is steadily released into the bloodstream over the four weeks. It may be given less frequently for secondary breast cancer. Your specialist can talk to you about this in more detail.

You may be given this injection as an outpatient at the hospital by your breast care nurse or at your GP practice. You may find it easier to make an appointment for your next dose after each injection so it’s given at the right time.

Goserelin is also available as a three-monthly injection for the treatment of other types of cancer. However, having goserelin in this way is not usually recommended for treating breast cancer as there is not enough evidence that it suppresses oestrogen levels enough. This is particularly important if you’re having goserelin alongside an aromatase inhibitor.

6. How long will I be given goserelin for?

If you have primary breast cancer, goserelin is usually given for up to five years or sometimes longer.

If you have , you will be given goserelin for as long as it keeps the cancer under control.

If you’re having goserelin to try to preserve fertility, an injection of goserelin is usually given before chemotherapy starts, then every four weeks during chemotherapy, and a last dose after the final chemotherapy treatment.

7. Will taking goserelin affect my periods?

During early treatment with goserelin some women may have some vaginal bleeding. If your periods continue, tell your treatment team as your ovaries may not be suppressed.

Within three weeks of the first injection, your oestrogen will be lowered to a level similar to that of a post-menopausal woman and your periods will normally stop. This effect is temporary and will only last for as long as you’re having goserelin.

When you stop having goserelin, your ovaries will usually start to produce oestrogen again. Most women’s periods will start again within three to twelve months after finishing treatment. However, if you’re approaching the age of natural menopause, your ovaries may not start working again.

If you’re concerned about going through an early menopause or would like to have children, you can discuss with your treatment team how long to continue goserelin.

8. Do I need to use contraception while taking goserelin?

You’re advised not to become pregnant while you’re having goserelin because the drug could harm a developing baby. It’s possible to become pregnant while having goserelin, even if your periods have stopped or become irregular.

Use a non-hormonal method of contraception to avoid getting pregnant, such as condoms, Femidoms or a diaphragm. It may also be possible to use a coil (IUD or intrauterine device). However, you would need to discuss this with your specialist as not all types are suitable for women with breast cancer.

9. What happens if I miss an injection?

If you miss an injection, try to have it as soon as possible.

10. What are the possible side effects of goserelin?

Like any drug, goserelin can cause side effects. Everyone reacts differently to drugs and some people have more side effects than others. Having few or no side effects doesn’t mean the drug isn’t effective. As goserelin can be given in addition to chemotherapy or other hormone therapies, it’s sometimes difficult to know which side effects are being caused by which treatment.

You can talk to your treatment team about any side effects you’re having from goserelin and how best to manage them.

Common side effects

The most common side effects of goserelin are menopausal symptoms such as:

Although these symptoms may be quite intense in the beginning, they usually improve over time.

After goserelin has been given, you may notice an area of redness or bruising at the injection site, but this should disappear within a few hours. Occasionally, bruising may be there for a few days.

Some women notice a change in their breast size. Acne (spots) is another commonly reported side effect that can appear on any part of the body.

Less common side effects

Less common side effects include headaches and tingling in fingers and toes. Some women have also reported weight gain, tiredness and nausea (feeling sick).

Low mood and depression

Some people experience low mood or depression. Talk to your GP or treatment team about how to manage a change in mood. Counselling, mindfulness and regular exercise can be helpful. Your GP or specialist can refer you for counselling or may suggest you take an antidepressant drug. Your breast care nurse may also be able to help or tell you about support services in your local area.

We’ve put together a mental health toolkit that may help you cope with the emotional side effects of breast cancer treatment.

Vaginal bleeding

During the first month of treatment you may have some vaginal bleeding caused by the withdrawal of the hormone oestrogen.

Joint pain and stiffness

When first starting goserelin treatment, some people notice joint pain and stiffness. This is due to the reduced oestrogen levels and usually improves over time. If it doesn’t, talk to your specialist or breast care nurse. It can usually be relieved with mild pain relief like paracetamol or an anti-inflammatory drug such as ibuprofen. Before using anti-inflammatory pain relief, ask your treatment team about the correct dose, how long you should use it for and any possible side effects, especially if you have a stomach ulcer or asthma.

Hair and skin changes

Goserelin can sometimes cause hair thinning. This is usually mild. People don’t always tell their treatment team about hair thinning when they’re having hormone therapy so it’s difficult to know how common this is. Some people also report a mild skin rash.

Blood pressure changes

Changes in blood pressure may occur. Blood pressure can be higher or lower than normal, but doesn’t normally need treatment or mean that goserelin has to be stopped.

Osteoporosis (thinning of the bone)

Lack of oestrogen over a long period of time can cause thinning of the bones (osteoporosis). Your treatment team may suggest a DEXA (dual energy X-ray absorptiometry) scan to check bone mineral density before you start goserelin.

If you’re concerned about your risk of developing osteoporosis, talk to your treatment team.

Tumour flare

If you’re given goserelin to treat secondary breast cancer in the bone, you may have an increase in your symptoms for a short time following the start of treatment (sometimes referred to as ‘tumour flare’).

High levels of calcium in the body

In rare cases some people with secondary breast cancer may have a temporary increase in the level of calcium in the blood. This can cause symptoms such as nausea, vomiting (being sick), constipation or drowsiness. If you experience any of these symptoms, contact your treatment team.

11. Further support

Join our online forum to chat to other people going through treatment at the same time as you.

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Quality assurance

This information was published in July 2020. We will revise it in July 2022.

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