Hormone Therapy for Breast Cancer
Types of Hormone Therapy
There are three main groups of drugs used in hormone therapy:
- Aromatase Inhibitors: These drugs are prescribed for women who develop breast cancer after the menopause. Hormone-dependent breast cancer needs the hormone estrogen to grow. Aromatase inhibitors decreases the body's estrogen by blocking an enzyme called aromatase from turning androgen into estrogen.
- Anastrozole (Arimidex)
- Exemestane (Aromasin)
- Letrozole (Femara)
- Selective Estrogen Receptor Modulators (SERMs)
: SERMs block the effect of estrogen on the breast tissue. Estrogen receptors are present in other parts of the body like the bones and uterus.
But the SERMs used in breast cancer act specifically on the receptors of the breasts - hence the term "selective". SERMS act on the receptors by sitting on their surface and preventing the estrogen from attaching to the cells. If estrogen isn't attached to a breast cell, the cell doesn't receive estrogen's signals to grow and multiply. There are three SERMs:
- Tamoxifen (Nolvadex)
- Raloxifene (Evista)
- Toremifene (Fareston)
- Estrogen Receptor Downregulators (ERDs): The action of ERDs are similar to SERMs - they block the estrogen receptors so that the estrogen cannot attach to the receptor. This prevents growth and multiplication of the cell. But they also work in two other ways - they can reduce the number of estrogen receptors and they can change the shape of breast cell estrogen receptors so they don't work very well.
There is only one ERD available:
- Fulvestrant (Faslodex)
In premenopausal women, the level of estrogen can be brought down by stopping the ovaries from producing estrogen or by removing the ovaries. This is called 'ovarian ablation'.
- Pituitary Downregulation The pituitary gland in the brain produces a hormone called FSH which stimulates the ovaries to produce estrogen. Certain drugs can act on the pituitary to prevent secretion of FSH. With less FSH in the blood, the ovaries are not sitmulated to produce estrogen. These drugs are also called LHRH analogues or 'luteinising hormone releasing hormone' analogues. The drugs commonly used are:
- Goserelin (Zoladex).
- Leuprolide (Lupron).
- Removal of the ovaries: The ovaries can be surgically removed, especially in women who are at high risk to develop hormone receptor positive breast cancer.