This information is about a hormonal therapy called exemestane, which is also commonly called Aromasin®. It should ideally be read with our general information about breast cancer or secondary breast cancer.

Aromasin is a type of hormonal therapy that is used in the treatment of breast cancer in women who have had their menopause (change of life).

Hormonal therapies interfere with the production or action of particular hormones in the body. Hormones are substances produced naturally in the body. They act as chemical messengers and help to control the activity of cells and organs.

There are several different types of hormonal therapy. Your doctor can discuss with you which is best for your situation.

Many breast cancers rely on the hormone oestrogen to grow.

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.

Aromasin is a drug that blocks the process of aromatisation, and reduces the amount of oestrogen in the body. Drugs that work in this way are known as aromatase inhibitors. Other aromatase inhibitors include Arimidex® (anastrozole) and Femara® (letrozole).

Aromasin is a tablet which is taken once a day, preferably after a meal and at the same time each day (it doesn't matter whether this is in the morning or the evening).

Doctors take into account many different factors when planning each person's treatment, so it is important to talk things over with your specialist. They will make a decision about treatment based on current medical knowledge and your individual situation.

Early breast cancer

Aromasin is used to treat post-menopausal women with early breast cancer (cancer that has not spread) after they have completed two or three years of tamoxifen treatment.

Advanced breast cancer

Aromasin is used to treat women who have advanced or secondary breast cancer (cancer that has spread to other parts of the body). It is also used to treat women whose breast cancer has come back after initial treatment.

Each person's reaction to any medication is different. Most people have very few side effects with exemestane, while others may experience more. The side effects described in this information will not affect everyone and may be different if you are having more than one drug.

We have outlined the most common side effects. However, we have not included those that are very rare and therefore extremely unlikely to affect you. If you notice any effects that you think may be due to the drug, but are not listed in the information, please discuss them with your doctor or nurse.

You will see your doctor regularly while you have this treatment so that they can monitor the effects. This factsheet should help you to discuss any queries about your treatment and its side effects with your doctor or nurse, who are in the best position to help and advise you.

Some people may have the following side effects to varying degrees. If any side effects occur they are usually mild.

Hot flushes and increased sweating These are usually mild and may wear off after a period of time. Sometimes women find that avoiding or cutting down on tea, coffee, nicotine and alcohol can reduce sweats. Recent research suggests that hormones called progestogens, or some antidepressants, may be helpful in controlling this side effect.

Some women find that complementary therapies help. Your GP may be able to give you details about getting these on the NHS. If you are having troublesome hot flushes you can discuss this with your doctor.

Feeling sick (nausea) Let your doctor know if this occurs, as it can usually be effectively treated. Feeling sick can often be relieved by taking your tablet with food or at night.

Feeling tired (fatigue) Fatigue is not a common problem. Getting plenty of rest can help.

Headaches These are not common, but if you have frequent headaches your doctor can prescribe medicines to help.

Difficulty sleeping Some women find that they have trouble sleeping while taking Aromasin. Having a warm bath or a hot milky drink before bed can be helpful. Using relaxation techniques or tapes may also help.

Abdominal pain and diarrhoea Rarely, Aromasin can cause diarrhoea. This can usually be controlled with medicine, but let your doctor know if it is severe. It is important to drink plenty of fluids if you have diarrhoea.

Hair thinning Some women notice that some of their hair falls out during the time that they are taking Aromasin. This is usually mild and the hair returns to normal at the end of treatment.

Risk of osteoporosis Women who have osteoporosis (weakened bones) or are at risk of it, should have their bone strength assessed before and during treatment with Aromasin. Some women may need to take bone-strengthening drugs to help prevent osteoporosis from developing.

Aromasin may be given over a number of years or for as long as it is controlling your cancer, depending on your individual situation. Your doctors will discuss the length of treatment that they feel is appropriate for you.

Aromasin may interact with other medicines. Let your doctor know about any medications 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, as Aromasin could harm them.
• 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. Let your doctor or nurse know. 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. Make sure that you have plenty for holidays.

This section has been compiled using information from a number of reliable sources, including:

• Martindale: The Complete Drug Reference (35th edition). Sweetman et al. Pharmaceutical Press, 2007.

• British National Formulary (56th edition). British Medical Association and Royal Pharmaceutical Society of Great Britain, September 2008.

For further references, please see the general bibliography.