Hormones are substances that occur naturally in the body, where they control the growth and activity of normal cells. Female hormones, particularly oestrogen, can encourage the growth of some breast cancer cells. Drugs which lower the level of oestrogen in the body, or that block oestrogen from attaching to the cancer cells, are used as treatment for some types of secondary breast cancer.

Many women are prescribed tamoxifen (one type of hormonal therapy) after their initial cancer treatment. For these women, if the cancer comes back, a different type of hormonal therapy such as an aromatase inhibitor may be used. Aromatase inhibitors are becoming more widely used after primary breast cancer treatment, and in this situation tamoxifen or a different type of aromatase inhibitor may be used if the cancer comes back. Some women have several types of hormonal therapy – one after the other.

Hormonal therapy only works for women who have oestrogen-receptor positive (ER+) cancers. They can be effective in controlling slow-growing cancers affecting the bones, the lymph glands, the fatty tissue under the skin or the skin itself. Hormonal therapy can also be used for secondary breast cancer in the liver and lung.

One advantage of hormonal treatments is that they are easy to take and although side effects can occasionally be troublesome, they are rarely serious. Another advantage is that there are many different hormonal treatments available so if one doesn’t work, or stops working, others can be tried. You will usually need to take hormonal therapies for a few weeks before your doctors can tell if they are working. Many hormonal treatments are available and more are being developed all the time.

The choice of hormonal therapy will depend upon whether you are pre or postmenopausal. Your doctor will be able to discuss which type of hormonal therapy treatment is best for you, based on all your relevant medical details.

After the menopause, oestrogen is produced mainly from male hormones (androgens) made by the adrenal glands. The androgens are changed into oestrogens in the fatty tissues of the body. Changing androgens into oestrogens is controlled by an enzyme called aromatase.

Postmenopausal women may be offered hormonal treatment with either an anti-oestrogen (such as tamoxifen) or an aromatase inhibitor.

Tamoxifen

Tamoxifen works by preventing oestrogen in the body from attaching to breast cancer cells and encouraging them to grow. It is used for both pre and postmenopausal women. Tamoxifen has been the most widely used hormonal therapy for breast cancer and it has been shown to be highly effective in reducing the chance of the cancer coming back. It can also be very effective in controlling secondary breast cancer for many women. Tamoxifen treatment can be continued for as long as it is effective in preventing the cancer cells from growing.

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.

For many women, these side effects are mild and may reduce over time. However, some women continue to find the side effects of tamoxifen are a problem. If this happens, it is helpful to discuss this with your doctor as there are sometimes ways of reducing the effects.

We have a section on breast cancer and menopausal symptoms which has helpful tips.

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

Women who have secondary breast cancer in a bone may find that tamoxifen makes the bone pain worse for the first few days. This is known as tumour flare and it soon eases, but it is important to know that it might happen and that it is a temporary side effect of the drug. You should tell your doctor if it happens.

Fulvestrant (Faslodex®)

Fulvestrant is a newer anti-oestrogen drug that is only used to treat postmenopausal women. It is given as an injection once a month. It may be used after treatment with tamoxifen or aromatase inhibitors. It may also be used if women can’t take tablets or may forget to take tablets. The side effects are similar to tamoxifen.

Aromatase inhibitors

Aromatase inhibitors work by blocking the production of oestrogen in the fatty tissues and the cancer itself, so they reduce the overall levels of oestrogen in the body and the cancer. Aromatase inhibitors are only used in postmenopausal women.

Aromatase inhibitors can cause thinning of the bones (osteoporosis). Women who already have osteoporosis, or are at risk of it, should have their bone strength checked before and during treatment with an aromatase inhibitor.

• Anastrozole (Arimidex®) is an aromatase inhibitor that is taken once a day as a tablet. Side effects include joint and muscle pain, vaginal dryness and nausea (feeling sick). It is slightly less likely to cause hot flushes than tamoxifen.

• Letrozole (Femara®) is also taken once a day as a tablet. Side effects are usually mild, and are similar to those of anastrozole.

• Exemestane (Aromasin®) is also taken as a tablet once a day. The side effects tend to be mild and are similar to anastrozole, but it may also cause diarrhoea in some women.

If the secondary breast cancer cells are not controlled by tamoxifen or aromatase inhibitors, artificial progesterone (progestogen) treatment may be used instead. Progesterone is a hormone that occurs naturally in women. Progestogens are stronger than progesterone and can be given as tablets or by injection into the muscle of the buttock. The commonest ones are megestrol acetate (Megace®) and medroxyprogesterone acetate (Farlutal®, Provera®). You may be given injections by your doctor or nurse.

Progestogens tend to cause more side effects than aromatase inhibitors. Although some women may feel slightly sick, most women find that progestogens increase their appetite. This may make them put on some weight, particularly in the stomach area. Some women also notice mild muscle cramps or slight vaginal bleeding (spotting). Rarely, progestogens can cause breathlessness. If this happens you should let your doctor know.

In women who have not had their menopause (change of life), most of the oestrogen in the body is produced by the ovaries. A small amount of oestrogen is made by changing androgens (produced by the adrenal glands) into oestrogen.

Premenopausal women may be offered hormonal treatment with the anti-oestrogen drug tamoxifen, or with a pituitary downregulator. They may also be offered treatment to stop the ovaries producing oestrogen, known as ovarian ablation.

Pituitary downregulators

Drugs known as pituitary downregulators reduce the production of oestrogen-stimulating hormones from the pituitary gland.

This lowers the level of oestrogen in the body. Pituitary downregulators can be used to lower oestrogen levels in women who have not yet had their menopause. Stopping the ovaries from producing oestrogen is sometimes called ovarian suppression. Using a pituitary downregulator has the same effect as removing the ovaries or giving them radiotherapy, but the effect is reversible. As a result, many doctors now recommend these drugs, rather than removing the ovaries with surgery or giving radiotherapy to stop them working.

They only work for oestrogen-positive breast cancers. The most commonly used pituitary downregulator for women with breast cancer is goserelin (Zoladex®). Goserelin brings on a temporary menopause, so many of its side effects are similar to those of the menopause and include hot flushes and sweating, joint pain, lowered sex drive, headaches and mood changes.

Many younger women find the symptoms of an early menopause difficult to deal with. Although some menopausal symptoms can be uncomfortable, many can be effectively treated.

Ovarian ablation

In women who have not yet had the menopause, it is sometimes possible to stop the growth of their secondary breast cancer by stopping the ovaries from producing oestrogen. This is known as ovarian ablation, and can be done either by removing the ovaries with an operation or by giving three or four radiotherapy treatments to the ovaries. In both cases, the ovaries stop producing female hormones, which brings on the menopause.

When surgery is used, periods stop immediately. You will need to stay in hospital for 1–2 days.

When radiotherapy is given to the ovaries, women usually have one more period, which may be heavy. Periods then stop completely. Contraception should be continued for three months after radiotherapy.

Unlike pituitary downregulators, these treatments will mean that a woman will no longer be able to have children. This definite end to being able to have children can be very distressing to women already coping with secondary breast cancer.

Healthcare staff will understand the emotional effect this treatment can have on women. You may find you want time to discuss the treatment with your partner, or someone close to you, before deciding to go ahead. You can also contact our cancer support service to talk through your feelings.