Toremifene (Fareston ®)
Toremifen is a hormonal therapy used to treat breast cancer. It is also called Fareston ®, but throughout this section we refer to it by its more commonly used name, toremifene.
This information describes toremifene, how it’s given and some of its possible side effects. It should ideally be read with our general information about secondary breast cancer.
You will see your doctor regularly while you have this treatment so they can monitor its effects. This information should help you discuss any queries about your treatment and its side effects with your doctor or specialist nurse.
Toremifene is a hormonal therapy used to treat women with breast cancer who have been through the menopause. It’s used to treat women whose cancer has spread to other areas of the body (secondary breast cancer).
Hormones are substances produced naturally in the body. They act as chemical messengers and help control the activity of cells and organs. Hormonal therapies interfere with the production or action of particular hormones.
The way toremifene works is not yet fully understood, but its main function is as an anti-oestrogen drug. This means that it interferes with the action of the female hormone oestrogen.
Many breast cancers rely on the hormone oestrogen to grow. Hormone-sensitive breast cancers have proteins called receptors on the breast cancer cells. They are known as oestrogen-receptor positive (ER-positive) breast cancers. When oestrogen comes into contact with the receptors, it fits into them and stimulates the cancer cells to divide so that the tumour grows.
Toremifene fits into the oestrogen receptor and blocks oestrogen from reaching the cancer cells. This means the cancer either grows more slowly or stops growing altogether.
How toremifene is taken
Back to top
Toremifene is a tablet that is taken once daily. It should be taken at approximately the same time each day.
Length of treatment with toremifene
Back to top
Your doctors will discuss the length of treatment they feel is appropriate for your situation. Toremifene may be given for as long as it is effective in controlling your cancer.
Possible side effects of toremifene
Back to top
Each person's reaction to any medicine is different. Some women have very few side effects while others may experience more.
We have outlined the most common side effects but haven't included those that are rare and therefore unlikely to affect you.
If you notice any effects that are not listed here, discuss them with your doctor or nurse.
Hot flushes and sweats
These are a common side effect of toremifene. They may gradually lessen over the first few months, but some women continue to have them for as long as they take toremifene.
There are a number of ways to help to reduce or control hot flushes and sweats. Some women find it helpful to avoid or cut down on tea, coffee, nicotine and alcohol.
Some drugs, including low doses of some antidepressants or the hormone progesterone, may be helpful in controlling this side effect. Your nurse or doctor can discuss this with you.
Some women may find complementary therapies, such as acupuncture, help. Your GP may be able to give you details about having these on the NHS.
We have more information about treatments for menopausal symptoms like hot flushes.
Diane shares her experience of coping with menopausal symptoms after treatment for breast cancer.
Feeling sick (nausea) and indigestion
Nausea and indigestion are fairly common but can often be relieved by taking your tablet with food or milk, or at night. Although nausea is quite common initially, it usually wears off after a few weeks.
Mood changes and tiredness (fatigue)
Toremifene may sometimes cause tiredness, dizziness and a low mood. Tell your doctor if you have these symptoms.
Vaginal bleeding or discharge
Let your doctor know if you have any vaginal bleeding or discharge.
Blurred or reduced vision is uncommon but let your doctor know about any changes to your eyesight.
Women who are prescribed toremifene for cancer that has spread to the bones may experience something called tumour flare when they start taking toremifene. This can cause a raised level of calcium in the blood (hypercalcaemia), with symptoms of nausea, vomiting and thirst. Occasionally, a short stay in hospital is needed until the calcium levels reduce.
Blood clots (thrombosis)
This is very rare. Signs of a blood clot include pain, warmth, swelling or tenderness in an arm or leg, or chest pain. Tell your doctor immediately if you have any of these signs. Toremifene isn't usually given to people who have had a blood clot in the past.
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.
Long-term side effects of toremifene
Back to top
Studies have shown that women who take high doses of toremifene over a long period of time may have a very slightly increased risk of developing cancer of the lining of the womb (endometrial cancer).
However, this small risk is generally outweighed by the benefits of taking toremifene. If detected early, treatment for endometrial cancer is usually very successful. An early warning sign is abnormal vaginal bleeding, although this is often caused by non-cancerous conditions such as polyps. If you have any abnormal vaginal bleeding, let your doctor know. Some women may have regular gynaecological check-ups.
Things to remember about toremifene tablets
Back to top
Toremifene may interact with other medicines. Tell your doctor about any medication you are taking, including non-prescribed drugs such as complementary therapies and herbal drugs.
Keep the tablets in a safe place, out of the reach of children.
Keep the tablets in the original packaging and store them at room temperature, away from direct heat and sunlight.
If your doctor decides to stop the treatment, return any remaining tablets to the pharmacist. Do not flush them down the toilet or throw them away.
Don't worry if you forget to take your tablet. Do not take a double dose. The levels of the drug in your blood will not change very much, but try not to miss more than one or two tablets in a row.
Remember to get a new prescription a few weeks before you run out of tablets and make sure you have plenty for holidays.
Additional information about toremifene
Back to top
If you’re admitted to hospital for a reason not related to the cancer, it’s important to tell the doctors and nurses looking after you that you’re having hormonal treatment. You should tell them the name of your cancer specialist so they can ask for advice.
It’s a good idea to know who you should contact if you have any problems or troublesome side effects when you’re at home.
This information has been compiled using information from a number of reliable sources, including:
British National Formulary. 64th edition. 2012. British Medical Association and Royal Pharmaceutical Society of Great Britain.
electronic Medicines Compendium (eMC) (accessed November 2012).
Sweetman, et al. Martindale: The Complete Drug Reference. 37th edition. 2011. Pharmaceutical Press.
With thanks to: Bruce Burnett, Teacher Practitioner in Clinical Pharmacy Practice; and the people affected by cancer who reviewed this edition. Reviewing information is just one of the ways you could help when you join our Cancer Voices network.