Anti-estrogens   Aromatase inhibitors   Ovarian suppression

Hormone therapy is the treatment of cancer with medication that interferes with the way the hormone estrogen works.

Estrogen is a naturally occurring hormone in the human body. In some people with breast cancer, the presence of estrogen can promote cancer cell growth. The hormone attaches to the cell surface at special points called estrogen receptors and speeds up the growth of that cell. These cancers are known as estrogen receptor-positive because they react to estrogen. If the effect of estrogen on these cells can be stopped, the growth of these cancers will be slowed down.

In other people, the breast cancer cell growth rate is not affected by the presence of estrogen, and these cancers are known as estrogen receptor-negative. For patients whose cancers are estrogen receptor-negative, there is likely no benefit to taking hormone therapy.

To determine the estrogen receptor status, cancer cells are tested in a lab. If they are found to be estrogen receptor-positive, then hormone therapy may help.

Hormone therapy is usually given after surgery, radiation therapy, and chemotherapy. The goal of hormone therapy is to block the way estrogen promotes the growth of estrogen receptor-positive breast cancers. It is intended to help reduce the risk of recurrence (the cancer coming back).

There are three main options for hormone therapy: anti-estrogens, aromatase inhibitors, and ovarian suppression.