What Is Hormone Therapy for Breast Cancer?

Hormones play a critical role in regulating sexual and other aspects of our physiology but certain breast cancers also use hormones as fuel. Medical researchers recognize this, and have developed various means of depriving these cancers of this advantage. These treatments, known as hormone or endocrine therapies, are often used in conjunction with surgery, to shrink tumors beforehand or to prevent the return of a cancer afterwards. Hormone therapy is a critical weapon in the medical war on breast cancer. 

How Does Hormone Therapy for Breast Cancer Work?

About 70 percent of all breast cancers are hormone receptor positive, meaning that cells associated with the disease have reception sites for one or both of the two primary female hormones, estrogen and progesterone. These substances, produced naturally by the body, are distributed via the bloodstream, and when they come into contact with a breast-cancer cell, they trigger its ability to grow and reproduce. This process is analogous to throwing a switch to power an engine. 

Hormone therapies are designed to reduce or eliminate contact between the hormones and breast-cancer cells. They do this in one of two ways: by blocking cell receptors from attaching hormones or by decreasing, in postmenopausal women, the body’s hormone production. 

Hormone therapy is conducted by means of medication. Most hormone-therapy drugs are taken daily in pill form; a few are injected. The drug or drugs selected by your physician will depend on several factors, such as your cancer’s stage of development, whether you’ve undergone menopause, and what other treatments, if any, you’ve received for your condition. You may undergo hormone therapy for three to six months prior to breast-cancer surgery, and for as many as five to ten years following a procedure.

What Drugs Are Used in Hormone Therapy for Breast Cancer?

Medications that prevent hormones from attaching to receptor sites include:

• Tamoxifen: Tamoxifen is generally used to block the recurrence of cancer in women who were treated during the disease’s early stages. It is used less often with advanced forms. Tamoxifen is appropriate for women who are either pre- or postmenopausal. The drug’s brand name is Nolvadex. 
• Toremifene: Toremifene is used with postmenopausal women that have a metastasizing cancer. It is marketed under the brand name Fareston. 
• Fulvestrant: Like toremifene, fulvestrant is used to treat advanced cancers in postmenopausal women. Fulvestrant’s trade name is Faslodex. 

The second major category of hormone-therapy drugs for breast cancer is known collectively as aromatase inhibitors. These decrease the amount of estrogen produced by a women’s body. Their use is limited to those persons that have undergone menopause either naturally or artificially (that is, as induced by medications or the surgical removal of the ovaries):

• Exemestane: Exemestane inhibits the return of breast cancer following treatment in an early stage of development. It is frequently administered in conjunction with tamoxifen. The brand name for this drug is Aromasin. 
• Anastrozole: Anastrozole stops estrogen production in postmenopausal women with early or advanced forms of breast cancer. It is marketed to the public as Arimidex. 
• Letrozole: Letrozole is typically used with women in the early stages of breast cancer, sometimes in connection with tamoxifen. Femara is the drug’s brand name.

There are several other hormone-therapy medications sometimes utilized in the treatment of breast cancer. One of these is leuprolide or Lupron, an estrogen-stoppage drug given to premenopausal women with breast cancer, and also useful in the treatment of prostate cancer in men.

What Are the Side Effects of Hormone Therapy for Breast Cancer?

Potential side effects of hormone therapy for breast cancer include:

• Stomach upset
• Fatigue or feelings of weakness
• Pain in joints and muscles
• Hot flashes
• Vaginal dryness, irritation, or discharge
• Loss of menstrual periods (in premenopausal women). 

More serious, but less frequent, side effects may include cataracts, osteoporosis, blood clots, stroke, heart ailments, and uterine or endometrial cancers. 

How Effective Is Hormone Therapy for Breast Cancer?

Hormone therapy for breast cancer has demonstrated effectiveness in:

• Reducing tumor size before a surgical procedure
• Stopping the spread of cancer to healthy breast tissue
• Limiting the spread of a cancer that has metastasized beyond the breast
• Preventing a cancer recurrence after successful treatment. 

There is also evidence that hormone therapy can decrease the incidence of breast cancer in women with elevated risk levels of developing the disease.