By examining breast cancer cells that have been removed during a biopsy, doctors are able to determine whether or not hormone therapy (not to be confused with hormone replacement therapy) will be an effective treatment for breast cancer. It is only if analysis shows that the breast cancer cells have so-called 'hormone receptors' on them that hormone therapy will be appropriate. If this is the case a tumour is described as being either oestrogen or progesterone receptor positive.
Hormone therapy lowers levels of these hormones in the body to deprive the cancer cells with these receptors of any stimulation, and slow their growth.
There are four main types of hormone therapy:
Examples of this type of treatment are Tamoxifen and Fulvestrant (commercial name Faslodex). These drugs prevent breast cancer cells from accessing any oestrogen in the body. Whereas some hormone treatments only work in either pre or post menopause patients, anti oestrogens work in both.
Aromatase Inhibitors only work for patients who are post menopause. They work by preventing androgens from being converted into oestrogen. Aromatase inhibitors treatments include anastrozole (e.g. Arimidex), letrozole (e.g. Femara) and exemestane (e.g. Aromasin).
As the name implies, ovarian suppression treatment blocks the function of the ovaries and so cuts off what is the main source of oestrogen in patients who are pre menopause. Hormone therapy ovarian suppression is temporary, unlike other methods of suppressing ovarian hormone production such as oophorectomy (surgical removal of the ovaries) or radiotherapy targeted at the ovaries. An example of an ovarian suppression drug is goserelin (Zoladex).
Progestins / Progestogens
This type of hormone therapy is reserved for use when the treatments listed above are ineffective. Progestins are in fact synthetic versions of progesterone, a female hormone. They are primarily used in patients with secondary breast cancer. Progestin treatments include megestrol acetate (Megace) and medoxyprogesterone (Provera).
Most hormone therapy treatments take the form of tablets taken orally.