1. What is goserelin (Zoladex)?
2. How does goserelin work?
How goserelin 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.
Goserelin will only be prescribed if your breast cancer is ER-positive, unless you’re having it to try to preserve fertility.
Before the menopause, oestrogen is mainly produced in the ovaries. Goserelin interferes with hormone signals from the brain that control how the ovaries work, switching off the production of oestrogen. This lowers oestrogen levels in the body, which may stop breast cancer cells from growing.
This is called ovarian suppression, but you may also hear it called ovarian function suppression (OFS) or ovarian ablation.
Why it’s given
Ovarian suppression can help reduce the risk of the breast cancer coming back (recurrence) or a new breast cancer developing (a new primary breast cancer).
Goserelin is also used in treatment for .
Who might benefit from having goserelin?
If you’re still pre-menopausal after chemotherapy, you could benefit the most from ovarian suppression. Younger women may get the greatest benefit from goserelin, so you might not get as much benefit from ovarian suppression if you’re over 35.
Your specialist will talk to you about whether ovarian suppression may benefit you.
3. Goserelin as a treatment for breast cancer
Goserelin is used as a treatment for some breast cancers. It can be given on its own, but it’s usually given with another hormone therapy, such as tamoxifen or an aromatase inhibitor.
Primary breast cancer
Goserelin is used to treat some pre-menopausal women with ER-positive primary breast cancer.
If you’re having goserelin as part of your treatment for primary breast cancer, it’s usually given for 5 to 10 years, depending on the features of your breast cancer and your menopausal status.
Secondary breast cancer
Goserelin is also used to treat pre-menopausal women with secondary breast cancer.
If you have secondary breast cancer, you will have goserelin for as long as it keeps the cancer under control.
Goserelin with tamoxifen or aromatase inhibitors
Having goserelin with another hormone therapy may reduce the risk of breast cancer coming back for some pre-menopausal women who have had chemotherapy.
Your specialist will discuss the possible benefits and side effects of having goserelin with tamoxifen or an aromatase inhibitor.
If you’re having goserelin with an aromatase inhibitor, you will start goserelin 6 to 8 weeks before starting treatment with an aromatase inhibitor. You should continue having goserelin while you’re taking the aromatase inhibitor.
Aromatase inhibitors are not used on their own as hormone therapy in pre-menopausal women. This is because they’re not an effective treatment while the ovaries are still making oestrogen. However, aromatase inhibitors can be given alongside goserelin. Your treatment team will discuss with you what they recommend and why.
4. Goserelin for preserving fertility during chemotherapy
Options for preserving fertility before and during treatment
Chemotherapy can cause damage to the ovaries. This can reduce the number and quality of eggs and affect your ability to become pregnant.
Whether your fertility is affected after chemotherapy depends on:
- The type of drugs used
- The dose given
- Your age
- What your fertility was like before breast cancer treatment
Some studies have shown that using hormone therapy drugs like goserelin to suppress the ovaries may protect them during chemotherapy. This is because goserelin temporarily "shuts down" the ovaries.
However, we don’t know how effective goserelin is as a method of preserving fertility. It cannot replace other fertility preservation methods like egg and embryo freezing.
If you want to try to preserve fertility during chemotherapy discuss this with your treatment team before starting treatment.
If you’re having goserelin to try to preserve fertility, you will usually have an injection of goserelin before chemotherapy starts, then every 4 weeks during chemotherapy. The last injection is after the final chemotherapy treatment.
You will not be able to take goserelin during pregnancy or while breastfeeding.
5. How is goserelin given?
Goserelin comes as an implant (a very small pellet) in a pre-filled syringe.
You will have it as an injection into the fatty tissue under the skin into your belly (abdomen). This is called a subcutaneous injection.
Having surgery to the abdomen, such as a DIEP reconstruction, should not stop you having goserelin. But talk to your treatment team if you have concerns about how the injection is given.
Your treatment team will give you the first injection at the hospital. You will usually have the next injections 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.
Some people find the injection uncomfortable. Your doctor can prescribe you a local anaesthetic cream to numb the skin before the injection. This will reduce any discomfort. However, you will need to wait for at least 1 hour after the cream has been applied before the area is numb. It’s important to ask about using this cream well in advance of your injection so it can be arranged in time.
It's recommended that goserelin is given every 28 days (4 weeks). The injection is called a “depot injection”, which means the drug is steadily released into the bloodstream over the 4 weeks.
Goserelin is also available as a 3-monthly injection. Your treatment team can advise whether this is the best option for you.
6. 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.
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.
For many people, side effects improve within the first few months of starting treatment. However, this may not be the case for you.
If you have any side effects while taking goserelin, whether they are listed below or not, talk to your GP or treatment team about how best to manage them.
Common side effects
Menopausal symptoms are the most common side effect of goserelin. These include:
- Hot flushes
- Night sweats
- Vaginal dryness
- A decrease in sex drive (libido)
Although these symptoms may be quite intense in the beginning, they usually improve over time.
Other common side effects
Other common side effects include:
- Soreness at the injection site
- Change in breast size
- Spots (acne)
- Joint pain and stiffness
- Hair and skin changes
- Blood pressure changes (this does not usually need treatment)
Less common side effects
Low mood and depression
Some people experience low mood or depression when taking goserelin.
You can 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 and 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.
You may have some vaginal bleeding during the first month of treatment. This is caused by the withdrawal of the hormone oestrogen. This is normal but let your treatment team know if it continues.
Osteoporosis (thinning of the bone)
Lack of oestrogen over a long period of time can cause osteoporosis (when bones lose their strength and are more likely to break). Your treatment team may suggest a DEXA (dual energy X-ray absorptiometry) scan to check your bone mineral density before you start goserelin.
Your treatment team will follow guidance when deciding whether to recommend a DEXA scan.
Guidance recommends people with early invasive breast cancer should have a DEXA scan if they’re not having bisphosphonate treatment and are starting ovarian suppression.
If you’re concerned about your risk of developing osteoporosis, talk to your treatment team.
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. This is 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 their blood. This can cause symptoms such as:
- Feeling sick (nausea)
- Being sick (vomiting)
If you have any of these symptoms, contact your treatment team.
Other less common side effects
Other less common side effects include:
- Tingling in fingers and toes
- Weight gain
- Feeling sick
7. Other important information
What happens if I miss an injection?
If you miss an injection, speak to your treatment team as soon as possible. It’s important to have your goserelin injections on time to make sure your ovaries remain suppressed. This will make goserelin as effective as possible.
Will goserelin affect my periods?
You may have some vaginal bleeding during early treatment with goserelin. Tell your treatment team if your periods continue, as your ovaries may not be suppressed.
Within 3 weeks of the first injection, your oestrogen will be lowered to a level similar to if you had been through the menopause. Your periods will normally stop. This effect is temporary and will only last for as long as you’re having goserelin.
Depending on your age when you stop having goserelin, your ovaries will usually start to produce oestrogen again. Most women’s periods will start again within 3 to 12 months of finishing treatment. However, if you have had chemotherapy, or 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 talk to your treatment team about how long to continue goserelin.
Do I need to use contraception while taking goserelin?
You’re advised not to become pregnant while you’re having goserelin. This is because the drug could harm a developing baby.
You can still become pregnant even if your periods have stopped or have become irregular. You should use a non-hormonal method of contraception, such as condoms, to avoid getting pregnant.
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.
8. Further support
Your treatment team and breast care nurse can help with any questions you have. You can also call us free on our helpline for information and support.
On our online forum, you can find people going through treatment at the same time as you.
If you are having goserelin for primary breast cancer, you can also speak to someone who has had a similar experience to you through our Someone Like Me service.