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Leuprorelin, also known as Prostap, is a hormone therapy used to treat breast cancer in women who've not been through the menopause.

1. What is leuprorelin (Prostap)?

Leuprorelin is a type of hormone (endocrine) therapy used to treat breast cancer in premenopausal women (women who have not been through the menopause). 

It is given as an injection. It can be given alone or with other hormone treatments.

Leuprorelin is the non‑branded name of the drug. Its current brand name is Prostap.

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

There are two different types of leuprorelin:

  • Leuprorelin (Prostap 3) 11.25mg (three-monthly)
  • Leuprorelin (Prostap SR) 3.75mg (monthly)

Leuprorelin can be used in primary breast cancer and .

2. How leuprorelin works

Some breast cancers use oestrogen in the body to help them grow. These are known as oestrogen receptor positive or ER-positive breast cancers.

Before the menopause, oestrogen is mainly produced in the ovaries. Leuprorelin ‘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.

3. Leuprorelin and breast cancer treatment

Leuprorelin 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 . The benefit may be more for younger women (less than 35 years) compared with women older than this.

Aromatase inhibitors are not used on their own as hormone therapy in premenopausal women. This is because they’re not an effective treatment while the ovaries are still making oestrogen, but they can be given alongside leuprorelin.

Leuprorelin will be given at least six to eight weeks before you start treatment with an aromatase inhibitor and should continue throughout it.

You will need blood tests before starting an aromatase inhibitor to make sure the ovaries are switched off. These blood tests should be repeated every 3 months during treatment with leuprorelin and an aromatase inhibitor.

It's important that leuprorelin injections carry on while you are having an aromatase inhibitor to make sure the level of oestrogen in the body doesn’t increase.

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 treatment team will discuss with you what treatment they recommend and why.

4. Can leuprorelin preserve fertility during chemotherapy?

Chemotherapy can cause damage to the ovaries, reducing the number and quality of eggs, and make it more difficult to get pregnant.

Some studies have shown that leuprorelin may protect the ovaries during chemotherapy as it temporarily shuts them down. But how effective leuprorelin is as a method of preserving fertility isn’t clear and cannot replace other fertility preservation methods.

Only monthly leuprorelin can be used to try to preserve fertility in premenopausal women with breast cancer who are having chemotherapy. It will normally be given as one injection two weeks before starting chemotherapy and then every month while you are having chemotherapy.

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

5. How is leuprorelin given?

Leuprorelin is given as an injection either:

  • Into muscle in your leg or buttocks
  • Under your skin (subcutaneously) into fatty tissue in your upper arm, thigh or abdomen

The injection site should be varied regularly.

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.

Missed injections

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

If an injection is missed, breakthrough bleeding may happen, or an egg may be released from the ovary. This could result in pregnancy and the aromatase inhibitor may stop working.

Talk to your treatment team if you miss an injection.

6. Side effects of leuprorelin

Like any drug, leuprorelin 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 leuprorelin 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 leuprorelin and how best to manage them, whether or not they are listed here.

Common side effects

Menopausal symptoms

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

  • Hot flushes
  • Night sweats
  • Vaginal dryness
  • A decrease in sex drive

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

Talk to your breast care nurse if menopausal symptoms are affecting your quality of life.

Breast tenderness

Breast tenderness is a common side effect. 

Redness or bruising at the injection site

After leuprorelin has been given, you may notice an area of redness or bruising at the injection site.

This should disappear within a few hours. Occasionally, bruising may be there for a few days.

Low mood and depression

Some people experience low mood or depression.

If you have a history of depression, you should be carefully monitored during treatment.

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 treatment team 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.

Muscle and joint pain

When first starting leuprorelin treatment, some people have joint pain and stiffness.

This is due to the reduction in oestrogen levels and usually improves over time. If it doesn’t, talk to your treatment team.

It can usually be helped 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 other health conditions.

Weight changes

If you lose your appetite, you may find eating small frequent meals or snacks helps keep up your food intake.  

If your appetite increases, it may affect your weight. Leuprorelin can sometimes cause fluid retention, which may affect weight.

If you struggle to maintain a healthy weight, ask your GP or treatment team about being referred to a dietitian.

Find out more about diet and breast cancer treatment.

Fatigue (extreme tiredness)

Fatigue is extreme tiredness that doesn’t go away with rest or sleep. It’s a very common side effect of breast cancer treatment and may affect you physically and emotionally.

Studies show that physical activity can help to relieve fatigue.

Find out more about fatigue and how to manage it.

Complementary therapies are also helpful for some people. 

Headaches, nausea and dizziness

Leuprorelin can sometimes cause headaches, nausea (feeling sick) and dizziness. 

These usually improve or become easier to manage over time. Mild pain relief such as paracetamol may help with headaches.

If you feel dizzy, avoid driving. If dizziness and the headaches don’t go away, see your GP. 

Abnormal sweating

Excessive sweating that is not related to heat or exercise is another possible side effect of leuprorelin.

Difficulty in sleeping

If you have difficulty sleeping (insomnia), some simple things like limiting caffeine in the afternoon and evening, keeping your room dark and quiet, and going to bed and getting up at a set time each day may help. 

Relaxation exercises can also be helpful. There are podcasts, phone apps or CDs that can guide you through these techniques. 

Your GP may prescribe something to help you sleep if the problem continues.

Other possible side effects

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 scan to check bone density before you start leuprorelin.

Find out more about looking after your bones.

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

High blood pressure and high cholesterol 

Leuprorelin can cause high blood pressure in some people. Your GP will be able to monitor and treat this if necessary. 

It may also cause the level of cholesterol in the blood to rise, although this doesn’t usually need treatment. If you have a history of high cholesterol discuss this with your treatment team or GP.

High levels of blood sugar

Leuprorelin can raise your blood sugar levels.

Signs of high blood sugar levels include feeling thirsty, needing to pass urine more often and feeling tired.

Tell your GP or treatment team if you have these symptoms.

Liver changes

Leuprorelin can occasionally cause changes to how the liver works.

These changes are usually very mild and unlikely to cause any symptoms. Once you finish your treatment your liver function will usually go back to normal.

7. How long will I be given leuprorelin for?

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

If you have secondary breast cancer, you may be given leuprorelin for as long as it keeps the cancer under control.

When you stop monthly leuprorelin injections, you will need to stop taking the aromatase inhibitor within one month of the last leuprorelin injection.

After you have stopped three monthly leuprorelin injections, stop taking the aromatase inhibitor within three months.

If you’re having leuprorelin to try to preserve fertility, an injection of leuprorelin is usually given at least two weeks before chemotherapy starts, then every four weeks during chemotherapy.

8. Will having leuprorelin affect my periods?

During early treatment with leuprorelin some women may have some vaginal bleeding. If this continues, tell your treatment team as your ovaries may not be switched off effectively.

After your leuprorelin injections, your oestrogen will be lowered to a level similar to that of a postmenopausal woman and your periods will normally stop. This effect is temporary and will only last for as long as you’re having leuprorelin.

When you stop having leuprorelin, 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 and periods may not return.

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 leuprorelin.

9. Contraception while taking leuprorelin

You’re advised not to become pregnant while you’re having leuprorelin because the drug could harm a developing baby.

It’s possible to become pregnant while having leuprorelin, 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 treatment team as not all types are suitable for women with breast cancer.

Leuprorelin is not suitable during pregnancy or while breastfeeding.

10. Further support

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

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Quality assurance

This information was published in January 2022. We will revise it in January 2024.

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