Hormone therapy for breast cancer

Hormone therapy, also called endocrine therapy or hormone-blocking therapy, slows or stops the effect of oestrogen. It is used to treat breast cancer that is hormone receptor positive. Hormone therapy is often used to lower the risk of the cancer coming back.

There are different types of hormone therapy. The type you have will depend on your age, the type of breast cancer and whether you have reached menopause.

Learn more about:

• Tamoxifen
• Aromatase inhibitors
• Ovarian suppression

Tamoxifen

Tamoxifen can be given to females of any age, regardless of whether they have reached menopause, and to males. It is commonly taken as a daily tablet for 5–10 years.

In females, tamoxifen can cause menopausal symptoms, although it does not cause menopause. In males, the side effects can include low sex drive (libido) and erection problems.

Side effects – Taking tamoxifen increases the risk of blood clots – see your doctor immediately if you have any swelling, soreness or warmth in an arm or leg. There is a small risk of developing cancer of the uterus (also called endometrial cancer) if you have gone through menopause, so see your doctor if you notice any unusual vaginal bleeding.

You will probably not experience all of these side effects. Side effects usually improve as treatment continues and after it has finished. Your doctor and breast care nurse can give you information about ways to manage the side effects of tamoxifen.

Aromatase inhibitors

After menopause, the ovaries stop making oestrogen, but small amounts are still made in body fat. Taking aromatase inhibitors will help reduce how much oestrogen is produced in the body.

Aromatase inhibitors are mostly used if you’ve been through menopause or had your ovaries removed. If you have not been through menopause and are at high risk of the cancer coming back, you may have aromatase inhibitors as well as an injection of goserelin (brand name Zoladex) to stop the ovaries producing oestrogen.

Examples of aromatase inhibitors include anastrozole, exemestane and letrozole. They are taken daily as a tablet, usually for 5–10 years.

Side effects – Aromatase inhibitors can cause thinning and weakening of the bones (osteoporosis). Your bone health will be monitored during treatment and your doctor may prescribe a drug to protect your bones.

Other side effects of aromatase inhibitors may include joint and muscle pain, vaginal dryness, low mood, hot flushes and weight gain. If you have arthritis, aromatase inhibitors may worsen joint stiffness and pain. Exercise or medicines from your doctor may help with this.

Ovarian suppression

If you have not been through menopause, drugs or surgery can stop the ovaries from producing oestrogen. This is known as ovarian suppression. It may also be recommended as an additional treatment for people taking tamoxifen or for premenopausal women taking an aromatase inhibitor instead of tamoxifen.

Temporary ovarian suppression

The drug goserelin (brand name Zoladex) stops oestrogen production. The drug is given as an injection into the belly once a month for 2–5 years to bring on temporary menopause.

Side effects – These are similar to those of permanent menopause. The drug may also be given to people having chemotherapy who wish to preserve their fertility because it helps protect the ovaries.

Permanent ovarian treatment

Ovarian ablation is treatment that permanently stops the ovaries from producing oestrogen. It usually involves surgery to remove the ovaries (oophorectomy).

Side effects – Ovarian ablation will bring on permanent menopause. This means you will no longer be able to become pregnant.

For more on this, see Fertility and Cancer.

→ READ MORE: Targeted therapy for breast cancer