Some cancers need female hormones (oestrogen) to grow and reproduce. In these cases hormone blocking therapy may be given to deprive the cancer cells of the hormones they need to grow.
How does it work?
Hormone blocking therapy is designed to either lower the level of oestrogen in your body or to stop the oestrogen from stimulating the cancer cells. Your doctor will probably recommend this treatment if your tumour is oestrogen or progesterone receptor positive.
There are different hormone blocking therapies for women who are pre-menopausal and those who are post-menopausal due to the different levels of oestrogen produced throughout these stages.
Some of the different hormone blocking therapies available include:
- Anti-oestrogens - stop oestrogen in the body from attaching to cancer cells (One of the most well-known hormone therapies is Tamoxifen).
- Aromatase Inhibitors (AIs) - block oestrogen production, but only work for post-menopausal women (common AIs used in Australia include Arimidex and Femara).
- Ovarian suppression - stops ovaries producing oestrogen, often recommended for women who haven't been through menopause. It may involve removing ovaries surgically, a short course of radiotherapy or a monthly injection.
- Progestogens - used if the secondary breast cancer cells are not controlled by anti-oestrogen treatments or aromatase inhibitors.
Side effects of hormone blocking therapy
- Some of the aromatase inhibitors (e.g. Arimidex) can cause joint pain and stiffness. They can also lead to bone loss. During this treatment you may be referred for bone density tests to monitor your bone density levels, particularly if you are at risk of developing osteoporosis. Bone density tests are usually done using DEXA X-ray. A bone density test is different from the bone scan that you may have to check whether your cancer has spread to other parts of your body. You may also have your Vitamin D levels checked. For more information about bone health and Vitamin D, read our Bone health page.
- Anti-oestrogen and Aromatase Inhibitors may cause hot flushes and vaginal dryness.
- Progestogens may cause nausea and can also increase appetite, which can lead to weight gain.
The page on managing symptoms and side effects may also be helpful.
Note: Hormone blocking therapy is sometimes confused with hormone replacement therapy (HRT), but they are completely different.
