There are many different types of hormonal therapy and they work in slightly different ways. They are often given after surgery and radiotherapy for breast cancer, to reduce the chance of the cancer coming back. Hormonal therapy is usually given after chemotherapy. Hormonal therapies are only effective in women whose cancer cells have receptors for oestrogen and/or progesterone on their surface. This is known as being oestrogen- receptor positive (ER+) or progesterone-receptor positive (PR+).

There are many issues to consider when deciding which type of hormonal therapy is appropriate for you, including:

• the stage and grade of the cancer
• which other treatments are being used
• whether the cancer cells are HER2-positive.

Tamoxifen has been the most widely used hormonal therapy for breast cancer and it has been shown to be effective in reducing the chance of the cancer coming back. Recently a new group of drugs known as aromatase inhibitors has been developed. Research has shown that for some women, giving aromatase inhibitors instead of tamoxifen, or after a period of tamoxifen treatment, can further reduce the chance of the cancer coming back.

Your doctor will be able to discuss which type of hormonal therapy treatment is best for you, based on all your relevant medical details. You may be advised to have:

• tamoxifen on its own for 5 years
• an aromatase inhibitor on its own for a few years
• tamoxifen for 2–3 years followed by an aromatase inhibitor for a few years
• tamoxifen for 5 years followed by an aromatase inhibitor for a few years.

Tamoxifen is known as an anti-oestrogen drug. It works by preventing oestrogen in the body from attaching to breast cancer cells and encouraging them to grow. It is used for women who have not yet had their menopause and may also be used for women who have had their menopause. For premenopausal women and women with very early-stage breast cancers, tamoxifen is the standard treatment.

It is available as tamoxifen and Nolvadex® and is taken as a daily tablet. The side effects may include:

• hot flushes and sweats
• a tendency to put on weight (although this may be due to other effects such as going into the menopause)
• dryness of the vagina or an increased discharge from the vagina.

These side effects are usually mild and may reduce over time. Some women continue to find some of the side effects of tamoxifen troublesome. If this happens, it is helpful to discuss this with your doctor as there are sometimes ways of reducing the effects. Our section on breast cancer and menopausal symptoms has some helpful tips.

In postmenopausal women, tamoxifen can slightly increase the risk of womb cancer, blood clots in the leg, and strokes. Although this sounds very frightening, these effects are very rare and are usually curable and treatable. The benefits of tamoxifen in reducing the chance of the breast cancer coming back far outweigh the risks of side effects for most women.

Aromatase inhibitors work by blocking the production of oestrogen in body tissues, so they reduce the overall levels of oestrogen in the body. Aromatase inhibitors are used only in postmenopausal women. The most commonly used are anastrozole (Arimidex®), letrozole (Femara®), and exemestane (Aromasin®).

For many postmenopausal women it is helpful to have an aromatase inhibitor as part of hormonal therapy treatment for early breast cancer.

Aromatase inhibitors, like all other medicines, may cause side effects. Many women can take aromatase inhibitors without any problems, but some may experience mild to moderate side effects. Unlike tamoxifen they do not increase the risk of blood clots and strokes. As aromatase inhibitors have only been used for a few years, the long-term side effects of taking them are not yet known. Some women find that they cause:

• hot flushes
• feelings of sickness
• joint pains
• vaginal dryness.

Taking aromatase inhibitors long-term may lead to the bones becoming more fragile. So, your doctor may do regular tests to check the strength of your bones and you may be advised to take medicines called bisphosphonates to prevent the bones becoming fragile. You will probably be advised to take calcium and vitamin D to maintain your bone strength – these are available from chemists. If you have osteoporosis (thinning of the bones), aromatase inhibitors may not be a suitable treatment. Your doctors can discuss this with you.

Zoladex is a type of drug known as a pituitary down-regulator, or LHRH analogue. It reduces the production of oestrogen-stimulating hormones by the brain. This lowers the level of oestrogen in the body in premenopausal women, but is reversible once the treatment is stopped.

Other ways of lowering the level of oestrogen include removing the ovaries or giving radiotherapy to the ovaries (see Ovarian ablation). Your doctor may give you a choice between Zoladex or these treatments.

As Zoladex brings on a temporary menopause, many of its side effects are similar to those of the menopause. They include hot flushes and sweating, a low sex drive, headaches and mood changes. It is given as a monthly injection just under the skin of the abdomen.