What is fulvestrant (Faslodex)?
This page is about fulvestrant (Faslodex) a hormone therapy for advanced breast cancer. There is information about
Fulvestrant (Faslodex) is a type of hormone therapy. It was licensed in the UK in 2004 for advanced breast cancer. Doctors can prescribe it for postmenopausal women with breast cancer that
- Has continued to grow, or has come back after treatment with another hormone therapy
- Is oestrogen receptor positive
If you have breast cancer that is oestrogen receptor (ER) positive, it means your breast cancer cells have areas on their surface called ‘receptors’ that oestrogen can attach to. Hormone receptors are also on normal cells. You can find oestrogen receptors on the cells of any body tissues that respond to oestrogen. Oestrogen can encourage cancer cells to grow and divide.
Some drugs, such as tamoxifen, can help stop oestrogen attaching to oestrogen receptors. This can stop the cancer coming back after surgery, chemotherapy or radiotherapy treatment, or can slow the growth of advanced cancer.
Another type of hormone therapy is aromatase inhibitors. These drugs work in a different way to tamoxifen. They can stop oestrogen being produced by the body in post menopausal women. The body produces oestrogen in a different way after the menopause.
Fulvestrant (Faslodex) is a new type of hormone therapy called an ‘oestrogen receptor antagonist’. It works in two ways. Firstly, it blocks oestrogen receptors, in a similar way to tamoxifen. But it can also change the shape of oestrogen receptors on cancer cells, so the oestrogen can’t attach to them. This effectively reduces the number of oestrogen receptors on the cell, and is called ‘down regulation’.
Fulvestrant has been tested in several clinical trials in various countries around the world. Results from trials so far show that it is at least as good as other hormone therapies, such as tamoxifen or anastrozole.
Tamoxifen and aromatase inhibitors often work very well for oestrogen receptor positive breast cancer. But eventually the cancer can become resistant to the treatment and start to grow again. When this happens, it can be very difficult to treat. Sometimes doctors then prescribe exemestane (Aromasin), another aromatase inhibitor. But doctors can now prescribe fulvestrant for women in this situation, giving a very useful extra treatment option.
Fulvestrant is still relatively new, and research needs to continue so we can find out more about it. A large trial called ‘SOFEA’ started recruiting patients in the UK in March 2004. They hope to recruit 750 women who have breast cancer that has continued to grow despite taking an aromatase inhibitor such as anastrozole. There are 3 groups in this trial
- One group of women has exemestane (the standard treatment at the moment)
- One group has fulvestrant alone
- The third group has both fulvestrant and anastrozole
The aim of this trial is to find out which of these treatments is best for advanced breast cancer. While this trial is open it will be listed on our clinical trials database. Choose ‘breast’ from the drop down menu.
Tamoxifen, anastrozole and exemestane are all tablets that you take every day, but fulvestrant is an injection that you have into a muscle (an intra muscular injection) once a month. Your doctor or nurse will give you 1 or 2 injections in your buttock every month.
You may have some soreness and swelling around the injection site for a day or 2 afterwards. But generally, fulvestrant appears to cause few side effects. Only 3 out of 100 women (3%) in clinical trials had to stop treatment because the side effects were too bad.
The most common side effects reported in clinical trials were
- Feeling or being sick
- Constipation or diarrhoea
- Headache
- Back pain
- Hot flushes
- Rash
- Soreness and redness at injection site
But remember, everyone reacts differently to different treatments. Just because a side effect has been reported in a trial, it doesn’t mean you will have it. You may have one or none of the side effects listed here. It would be very unusual to have them all.
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