This page discusses the use of hormone therapy for the treatment of breast cancer. For a thorough review of hormone therapy for cancer treatment, please see the hormone therapy treatment monograph.

Hormones are chemical messengers that regulate specific body functions, such as reproduction. They are produced by various glands in the body and enter the bloodstream where they travel to other tissues and exert their influence. Hormone therapy is used in cancer treatment to augment or interfere with the activity of certain hormones that can influence the growth of tumors.

Who Can Benefit from Hormone Therapy

Hormone therapy is designed to take advantage of the fact that many breast cancers are hormone sensitive. Breast cancer that is hormone sensitive may be estrogen receptor positive or progesterone receptor positive depending on which hormone they react to. The hormones, estrogen or progesterone, are able to bind to cancer cells and stimulate growth and division. Hormone therapy prevents the binding of these hormones to the cancer cells. This stops the cells from growing and, in doing so, prevents or delays breast cancer recurrence. It can also lower the risk of a second, independent breast cancer.

Tissue testing can determine if a cancer is sensitive to hormones. Cancers that are not hormone receptors positive do not appear to benefit from hormone therapy, either to prevent recurrence, or to prevent second cancers.

Talk with Your Doctor about this Treatment

While the vast majority of women who have hormone-sensitive breast cancer will benefit from hormone therapy, there may be times when the risks may outweigh the potential benefits. Your doctor will help you weigh the risks and benefits.

Methods of Hormone Therapy

The goal of hormone therapy is to prevent hormones from attaching to cancer cells and helping cancer grow. This may be done in a number of ways:

  • Medications are used to block the function of hormones
  • Destruction of ovarian tissue to suppress hormone production in the ovaries—ablation can be done with medications, radiation, or surgery
  • Medications are used to suppress hormone production outside of the ovaries by other tissues
  • Hormone therapy may include:

  • Selective estrogen receptor modulators (SERMs)
  • Aromatase inhibitors
  • Estrogen receptor down-regulators
  • Luteinizing hormone-releasing hormone (LHRH) agonists
  • Other hormonal agents, including androgens
  • Ovarian ablation
  • Selective Estrogen Receptor Modulators (SERMs)

    A commonly used selective estrogen receptor modulator (SERM) is raloxifene. This medication is used to treat osteoporosis. In postmenopausal women with osteoporosis who have been treated with raloxifene, this medication has been shown to reduce the risk of breast cancer.

    Raloxifene is not yet approved for use in breast cancer treatment. Its benefits, compared to tamoxifen, are being evaluated in the STAR prevention trial. Some reports have found a lower risk of uterine cancer among women taking raloxifene as compared with women taking tamoxifen. The development of uterine cancer is known to be influenced by estrogen-like activity. Raloxifene has been associated with an increased risk of blood clots.