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. It is also used to reduce the risk of certain conditions, including LCIS and some DCIS, developing into invasive breast cancer.

There are different types of hormone therapy – the one you have depends on your age, type of breast cancer and if you have reached menopause.

Learn more about:

• Tamoxifen
• Aromatase inhibitors
• Ovarian suppression

Tamoxifen

Tamoxifen is suitable for anyone, whether you have been through menopause or not. You need to take a daily tablet for 5–10 years.

Side effects – In females, tamoxifen can cause menopausal symptoms, although it doesn’t bring on menopause. In males, the side effects can include low sex drive (libido) and erection problems. Tamoxifen increases the risk of blood clots – see a doctor immediately if you have swelling, soreness or warmth in an arm or leg. There is a very small risk of developing cancer of the uterus (also called endometrial cancer), particularly if you have gone through menopause. Let your treatment team know if you have any unusual vaginal bleeding.

You are unlikely to have all of these side effects, and they usually improve as treatment continues and after it ends. Your doctor and breast care nurse can help you to manage any side effects.

Aromatase inhibitors

After menopause, the ovaries stop making oestrogen. However, both females and males make small amounts of oestrogen in body fat and the adrenal glands. Taking aromatase inhibitors will help reduce how much oestrogen is made in the body. This is important because oestrogen can cause some cancers to grow.

Aromatase inhibitors are mostly used if you have been through menopause, have had your ovaries removed or are male. They are sometimes used if you haven’t been through menopause, but have a high risk of the cancer returning. In this case, you may also be given an injection of goserelin, at least a week before chemotherapy starts, to stop your 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 you may be prescribed a drug to protect your bones. Consider seeing a physiotherapist or exercise physiologist for an exercise plan. Other side effects 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.

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 stops oestrogen production. It is given as an injection into the belly once a month for 2–5 years to bring on temporary menopause. Side effects are similar to those of permanent menopause. The drug may also help protect the ovaries during chemotherapy, so it is often given to people who want to preserve their fertility.

Permanent ovarian treatment

Ovarian ablation permanently stops the ovaries from producing oestrogen. It usually involves surgery to remove the ovaries (oophorectomy). Sometimes radiation therapy is used. Ovarian ablation will bring on permanent menopause. This means you will no longer be able to fall pregnant naturally.

→ READ MORE: Targeted therapy for breast cancer