Hormonal therapy is used to prevent the growth, spread, or recurrence of breast cancer. A pathology test on a sample of tumor tissue will reveal if the cancer has estrogen and progesterone receptors. If it has estrogen receptors, it is said to be estrogen-receptor positive; if not, it is said to be estrogen negative. The same is true of progesterone receptors.
When a tumor is said to be estrogen-positive or progesterone-positive, it means the tumor depends on the patient's natural hormones to grow.
Research has shown that if a tumor is estrogen-receptor positive, anti-estrogen therapy, such as the drug tamoxifen (Nolvadex), will block the receptor and prevent growth of cancer. Tamoxifen is used with and without chemotherapy primarily to treat women over 50. Some experts believe it is reasonable to give tamoxifen alone to low-risk, postmenopausal women and along with chemotherapy to high-risk, postmennopausal women.
Since Tamoxifen causes side effects similar to those of menopause—weight gain, hot flashes, and mood swings—younger women may choose not to take it. Most women continue on hormone therapy for two to five years, but research has not yet determined the optimal and safe duration of therapy.
There are obvious benefits to tamoxifen, but it is not without risk. Some studies have shown there may be an increased risk of endometrial cancer. Large studies are now being conducted to determine if tamoxifen will prevent cancer entirely in high-risk women. In some rare cases, removal of the ovaries is recommended, resulting in a surgically created menopause.
Clinical trials using aromatase inhibitors such as anastrozole, exemestrane and letrozole alone or in combination with Tamoxifen have shown a signification decrease in recurrence but only a small possible improvement in overall survival.
To learn more about hormonal therapy, see the Cancer Treatment module.