Letrozole (Femara ®)
This information is about a hormonal therapy drug called letrozole, which is also called Femara ®. It is used to treat breast cancer. Throughout this information we refer to it by its more commonly used name, Femara.
Femara is a type of hormonal therapy used to treat breast cancer in women who have been the through the menopause.
Hormones are substances produced naturally in the body. They act as chemical messengers and help control the activity of cells and organs. Hormonal therapies work by interfering with the production or action of particular hormones in the body.
Many breast cancers rely on the hormone oestrogen to grow. These cancers are known as oestrogen-receptor positive or ER-positive breast cancers. These breast cancer cells have receptors, which allow particular types of hormones to attach to the cancer cell.
In women who have had their menopause, the main source of oestrogen is through the conversion of androgens (sex hormones produced by the adrenal glands) into oestrogens. This is carried out by an enzyme called aromatase. The conversion process is known as aromatisation and happens mainly in the fatty tissues of the body.
Femara blocks the process of aromatisation and so reduces the amount of oestrogen in the body. As less oestrogen reaches the cancer cells, they grow more slowly or stop growing altogether.
Drugs that work in this way are known as aromatase inhibitors. Other aromatase inhibitors include anastrozole (Arimidex ®) and exemestane (Aromasin ®).
Femara is used to treat postmenopausal women with oestrogen-receptor positive breast cancer.
Your doctor will take into account a number of different factors when planning your treatment.
Early breast cancer
Femara may be given to women with early breast cancer (cancer that hasn't spread) after they have had surgery to remove the cancer. Giving treatment after surgery to reduce the risk of the cancer coming back is known as adjuvant therapy. Hormonal therapy is usually given for five years, but in some situations it may be given for longer.
Femara may sometimes be given to women after they’ve had five years of treatment with another hormonal drug called tamoxifen.
Sometimes Femara is given before surgery to women with localised early breast cancer, to allow them to have a lumpectomy (removal of the lump) rather than a mastectomy (removal of the breast). Giving treatment before surgery is known as neo-adjuvant therapy.
Advanced breast cancer
Femara may be used to treat women whose breast cancer has spread to other parts of the body (advanced or metastatic breast cancer). It can also be used to treat women whose cancer has come back after treatment with other hormonal therapies.
Femara is a tablet that’s taken once a day, ideally at about the same time each day. It doesn't matter whether you take it in the morning or the evening.
Your doctors will discuss the length of treatment they feel is appropriate for your situation. Femara is often given over a period of years or for as long as it is effective in controlling your cancer, depending on your individual situation.
Each person's reaction to any medicine is different. Some people have very few side effects while others may experience more. The side effects described here will not affect everyone and may be different if you’re having more than one drug.
We have outlined the most common side effects but haven't included those that are rare and unlikely to affect you. If you notice any effects that are not listed here, discuss them with your doctor or nurse.
You may have some of the following side effects, to varying degrees:
These are usually mild and may wear off after a period of time. Some people find it helpful to cut down on tea, coffee, nicotine and alcohol. Research suggests that hormones called progestogens or some types of antidepressants may be helpful in controlling this side effect. Your nurse or doctor can discuss this with you.
Some people find complementary therapies such as acupuncture helpful. Your GP may be able to give you details about having these on the NHS.
You can read more about treatments for menopausal symptoms like hot flushes in our section about breast cancer and menopausal symptoms.
Muscular aches and joint pain
Some women have pain and stiffness in their joints while taking Femara. Let your doctor know if these effects are a problem. You may find it helpful to take mild painkillers.
Feeling sick (nausea) and being sick (vomiting)
These effects can usually be treated effectively, so let your doctor know if they occur. Feelings of sickness can often be relieved by taking your tablet with food or milk, or at night.
Tiredness and headaches
It's important to get enough rest. If you feel sleepy, do not drive or operate machinery. Let your doctor know if you are getting headaches, as medicines can be prescribed to help.
Some women notice that their hair thins while taking Femara, but this is usually mild.
Risk of osteoporosis
Women who have, or are at risk of, osteoporosis (weakened bones), should have their bones assessed before and during treatment with Femara. Some women may need to take bone-strengthening drugs to help prevent osteoporosis from developing.
This may occur while using Femara. Gels that can help to overcome the dryness are available. These can be bought from a chemist or be prescribed by your doctor.
Femara can cause skin rashes. It’s important to let your doctor know if this happens. Your doctor can prescribe medicine to help with this.
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.
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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 are having hormonal treatment. You should tell them the name of your cancer specialist so they can ask them 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. Your doctor or specialist nurse will be able to provide you with details of who to contact for advice.
Things to remember about Femara tablets
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Femara may interact with other medicines. Let your doctor know about any medication you are taking, including non-prescribed drugs such as complementary therapies, vitamins 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.
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.
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.
Remember to get a new prescription a few weeks before you run out of tablets and make sure that you have plenty for holidays.
This section has been compiled using information from a number of reliable sources, including:
British National Formulary. 63rd edition. 2012. British Medical Association and Royal Pharmaceutical Society of Great Britain.
electronic Medicines Compendium (eMC). www.medicines.org.uk (accessed September 2012).
Early and locally-advanced breast cancer: diagnosis and treatment. 2009. National Institute for Health and Clinical Excellence (NICE).
Sweetman, et al. Martindale: The Complete Drug Reference. 37th edition. 2011. Pharmaceutical Press.
Thanks to Bruce Burnet, Consultant Pharmacist, and the people affected by cancer who reviewed this information. Reviewing information is just one of the ways you could help when you join our Cancer Voices network.