Breast Cancer > Receptors

  • The normal breast is influenced by the female sex hormones oestrogen and progesterone, which are produced naturally in your body. Oestrogen is the most important growth factor for breast cancer.
  • For a breast cancer cell to grow under the influence of oestrogen, it must already possess a protein called the oestrogen receptor (ER). The ER can be thought of as a lock opened by a key – oestrogen – to allow the cell to grow. The pathologist can stain a tumour sample with a dye to detect the ER.
  • If the ER is present in your tumour (an ER-positive tumour), you can be treated with hormonal drugs, such as tamoxifen, that block the effect of oestrogen.
  • Another way of stopping the action of oestrogen is by preventing the body from making it. In younger women, drugs that interfere with the ovaries can be used. For postmenopausal women, drugs that prevent oestrogen being made in fatty tissue called aromatase inhibitors (AIs) are effective. Examples include anastrozole, letrozole and exemstane. Most postmenopausal women will be prescribed an AI at some stage.
  • Another class of drugs interferes with a type of receptor called HER2. The anti-HER2 drug Herceptin is given in combination with chemotherapy to the minority of women who have HER2-positive breast cancer.