Endocrine therapies are drugs used to treat hormone receptor positive breast cancer. Around two-thirds of breast cancers are hormone receptor positive, which means that they need female hormones (oestrogen and/or progesterone) to grow and reproduce. Most women with hormone receptor positive breast cancer will be offered hormone therapy.
Endocrine therapy is given as an oral medication. It is usually taken daily for at least five years after the completion of your other breast cancer treatments (surgery, chemotherapy and/or radiotherapy).
Tamoxifen is one of the best known endocrine therapy medications. It can be used to treat pre and post-menopausal women. Arimidex, Aromasin and Femara (and new generic brands of these drugs) are also endocrine therapies, however they are only suitable for women who have completed menopause.
Endocrine therapy is sometimes confused with hormone replacement therapy (HRT), but they are completely different.
How does endocrine therapy work?
Endocrine therapy works by stopping oestrogen from ‘feeding’ the breast cancer cells. It has been found to be very effective in reducing the risk of the cancer spreading to other parts of the body, or of a new breast cancer developing in the same or other breast.
Recent research has shown that, for some women, taking tamoxifen for 10 years is better than five. Your medical oncologist will be able to talk to you about whether continuing tamoxifen beyond five years could be of benefit to you.
Endocrine therapy can have side effects, including:
- Menopausal symptoms such as hot flushes, night sweats, heart palpitations
- Sleep disturbance
The aromatase inhibitors can also cause pain, joint stiffness and vaginal dryness. Generally, these side effects can be managed. If you are finding side effects difficult to manage, talk to your medical oncologist. She or he may be able to switch you to one of the other hormone therapy drugs.
Some endocrine therapy treatments can cause bone density loss. This can result in bone fractures and osteoporosis. Your doctor may recommend that you have a bone mineral density scan, called a DXA or DEXA scan, before starting your treatment. You may also have your calcium and Vitamin D levels checked.