Hormones are substances produced naturally in the body. They act as chemical messengers and help control the activity of cells and organs. Hormonal therapies are drugs that interfere with the way hormones are made or how they work in the body.

Many breast cancers rely on the hormone oestrogen to grow. This type of breast cancer is called oestrogen receptor-positive (ER positive) breast cancer.

Before menopause, almost all oestrogen in women is made by the ovaries. Goserelin stops the ovaries making oestrogen.

Goserelin is used to treat ER positive breast cancer in women who have not yet had their menopause.

It may be used after surgery to reduce the chance of the cancer coming back. It may also be used to slow and control the growth of breast cancer that has spread to other parts of the body (advanced or metastatic cancer).

Your doctor will explain how long you are likely to have this treatment for.

You have goserelin as a very small pellet injected under the skin (subcutaneously). It is usually injected in the tummy area. The pellet releases the drug slowly as it dissolves under the skin. It is usually given every four weeks.

The injections can be given by your GP or practice nurse at the surgery. If you are not able to visit the surgery, a district nurse may give you the injection at home.

Some people may find the injection uncomfortable and notice redness or a darker colour around the area afterwards. You may have a local anaesthetic cream to numb the area before the injection.

If an injection is delayed by two or three days, this should not make a great difference. But you should try to have your injections on time as much as possible.

We explain the most common side effects of goserelin here. We also include some rarer side effects. You may get some of the side effects we mention, but you are very unlikely to get all of them. If you are having other drugs as well, you may have some side effects that we don’t list here.

You will see a doctor or nurse regularly while you have this treatment. Always tell your doctor or nurse about the side effects you have. They can give you advice about managing them, and may be able to prescribe drugs to reduce certain side effects.

More information about this drug

We are not able to list every side effect for this treatment here, particularly the rarer ones. For more detailed information you can visit the electronic Medicines Compendium.

Change in periods

Some women have vaginal bleeding during the first few weeks of having goserelin. Let your doctor know if it continues.

Your periods will usually stop while you are having this treatment. This is an expected effect, and is caused by the lower levels of oestrogen in the body. When you finish goserelin treatment, your periods are likely to start again. But some women go through their natural menopause during treatment and their periods don’t come back.

Even if your periods stop, you can still become pregnant. Goserelin is not a contraceptive drug. You need to make sure that you use effective contraception while having goserelin. You can discuss this with your doctor or nurse.

Tumour flare

Your oestrogen levels may go up in the first few days or weeks after starting goserelin. This is temporary but may make symptoms caused by advanced breast cancer worse. Doctors call this tumour flare.

If you have breast cancer that has spread to the bones, goserelin can cause high calcium levels in the blood (hypercalcaemia). If your calcium is high, you may feel sick or be sick (vomit), be very thirsty, constipated or, sometimes, confused. If you have any of these symptoms, let your doctor know straight away so they can treat it.

Hot flushes and sweats

These are common. Hot flushes and sweats may lessen after the first few months. Cutting down on nicotine, alcohol and hot drinks containing caffeine, such as tea and coffee, can help. Dress in layers, so you can remove clothes as needed. Natural fabrics, such as cotton, may feel more comfortable.

If hot flushes are troublesome, tell your doctor. Low doses of certain anti-depressant drugs can help to reduce flushes.

We have more information about treatments for menopausal symptoms, like hot flushes.

Loss of sex drive (libido)

Many women have a lower sex drive during treatment with goserelin. This usually continues for as long as the treatment is given. Some women also have vaginal dryness. Lubricating gels can help. These are available from a pharmacist or your doctor can prescribe them. Talk to your doctor or nurse for more information. We have more information about coping with sexual difficulties.

Skin rashes

You may get a skin rash that looks like acne.

Always tell your doctor or nurse about any skin changes. They can give you advice and may prescribe creams or medicines to help. Any changes to your skin are usually temporary and improve when treatment finishes.

Hair thinning

Some women notice that their hair becomes thinner while having goserelin. This is usually mild and goes back to normal after treatment finishes.

Mood changes

Some women have mood changes, or feel low or depressed when having goserelin. Let your doctor or nurse know if this is a problem, especially if you feel low most of the time or think you may be depressed.

Headaches

Tell your doctor or nurse if you have headaches. They can usually be controlled with painkillers you can buy without a prescription.

Sore joints

You may have pain and stiffness in your joints while having goserelin. Let your doctor and nurse know if this happens. They can prescribe painkillers and give you advice. Regular physical activity and keeping to a healthy weight can help reduce joint pain and help to keep your joints flexible.

Bone thinning

Having goserelin for a few years may increase your risk of bone thinning, which is called osteoporosis. This can increase your risk of a broken bone (fracture). You will usually have bone density scans to check the bone thickness before and during treatment. Some women may need treatment for osteoporosis. We have more information about how cancer treatments may affect bone health.

Tingling fingers and toes

Goserelin may cause changes in sensation in the hands and feet. This is usually mild. Let your doctor or nurse know if you have this.

Blood pressure changes

Goserelin may cause low or high blood pressure. Tell your doctor or nurse if you have ever had any problems with your blood pressure. Let them know if you feel dizzy or have any headaches.

Always let your doctor or nurse know about any side effects you have. There are usually ways in which they can be controlled or improved.

Contraception

Your doctor will advise you not to become pregnant when you’re having goserelin. This is because it may harm a developing baby. It’s important to use an effective, non-hormonal form of contraception during treatment and for a few months after it finishes. Even if your periods have stopped or are irregular you still need to use contraception. You can talk to your doctor or nurse about this.

Other medicines

Goserelin can interact with other drugs. This includes medicines you can buy in a shop or chemist. Tell your doctor about any medicines you are taking, including ones you can buy for yourself, complementary therapies, vitamins and herbal drugs.

Medical or dental treatment

If you need to go into hospital for any reason, always tell the doctors and nurses that you are having goserelin. Explain you are having hormonal therapy and that no one should stop or restart it without advice from your cancer doctor. Tell them the name of your cancer doctor so they can ask for advice.

Always tell your dentist you are having goserelin before having any dental treatment.