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Hormone Therapy for Treatment of Breast Cancer

Breast Cancer

A diagnosis of breast cancer can be devastating, but it's important to know that there are new therapies available to treat it. Breast cancer is the most common cancer in women, other than skin cancer, and is the second deadliest in U.S. women, following lung cancer.

The good news is that the number of deaths caused by breast cancer has declined significantly in recent years, due in large part to improved screenings and advancements in medicine that help women combat breast cancer. One such advancement is hormone therapy. Hormone therapy is a type of adjuvant therapy—like radiation and chemotherapy—that may be used in addition to surgery to kill any cancer cells that may have spread.

In deciding whether adjuvant treatment is necessary, your doctor takes into account the extent (stage) and nature of your cancer, general health and other factors.

Although the cause of breast cancer is typically unknown, researchers have identified risk factors that make some women more prone to developing it. Hormones are among those factors. Research indicates that breast cancer risk increases when breast tissue is exposed to high levels of hormones for long periods. This can be due to beginning menstruation at an early age or experiencing menopause at a late age or having children later in life or not at all. Studies also indicate that long-term use of birth control methods that contain both estrogen and progestin, a synthetic form of progesterone, and long-term use of hormone replacement therapy may increase breast cancer risk slightly; however, the risk from birth control hormones disappears 10 years after stopping usage.

Hormones aren't all bad, though. Just as estrogen and progesterone can cause some breast cancers to grow, hormone therapy can be used to slow or stop the growth of these tumors. Hormone therapy deprives cancer cells of the female hormone estrogen, which some breast cancer cells need to grow.

How Hormones Affect Breast Cancer

Hormones function as chemical messengers in your body. They affect the actions of various cells and tissues. The hormones estrogen and progesterone, which are produced by the ovaries in premenopausal women and by some other tissues in lesser amounts in all women, can promote the growth of certain breast cancers, known as hormone-sensitive breast cancers.

These breast cancer cells contain proteins known as hormone receptors. They are activated when hormones bind to them, which can lead to the stimulation of cell growth.

If you have been diagnosed with breast cancer, your health care professional likely will test samples of your tumor tissue that have been surgically removed to find out whether the cancer cells contain hormone receptors. If the tumor cells contain estrogen receptors, the cancer is called estrogen receptor-positive (ER-positive), estrogen-sensitive or estrogen-responsive. Similarly, if the cells contain progesterone receptors, the cancer is called progesterone receptor-positive (PR- or PgR-positive). About 70 percent of breast cancers are ER-positive, and most of those are also PR-positive.

Positive results indicate that a hormone being produced in the body is helping the cancer grow and hormone therapy may prevent it. Hormone therapy will not work if your cell tests are negative.

How Hormone Therapy Works

Hormone therapy, also called hormone treatment or endocrine therapy, can slow or block the growth of hormone-sensitive tumors by interfering with the hormone action or by blocking your body's ability to produce hormones.

Here are a few ways that cancer can be treated with hormone therapy:

  • Block estrogen production: The body uses an enzyme called aromatase to make estrogen, so drugs called aromatase inhibitors can be used to block estrogen production. They are used primarily in postmenopausal women, because premenopausal women produce too much aromatase for the inhibitors to block effectively. They are sometimes used in premenopausal women in combination with a drug to suppress ovarian function.
  • Block effects of estrogen: Several types of drugs interfere with estrogen’s ability to stimulate the growth of breast cancer cells. The best-known of these are selective estrogen receptor modulators (SERMs), which bind to estrogen receptors to block estrogen activity. Tamoxifen, a type of SERM, has been used for more than 30 years to treat hormone receptor-positive breast cancer.
  • Block ovarian function: This can be done temporarily using drugs called gonadotropin-releasing hormone (GnRH) agonists, which interfere with signals from the pituitary gland that stimulate the ovaries to produce estrogen. The ovaries' estrogen production also can be permanently stopped through ovarian ablation, either by surgical removal or radiation treatments.

Several studies have compared aromatase inhibitors with tamoxifen as adjuvant therapy in post-menopausal women with breast cancer and found that aromatase inhibitors better reduce the risk of cancer recurrence than using tamoxifen by itself for five years. The drug schedules that appear to be the most helpful include the following:

  • Tamoxifen for two to three years followed by an aromatase inhibitor to complete five years of total treatment
  • Tamoxifen for five years, followed by an aromatase inhibitor for five years
  • An aromatase inhibitor for five years

When Is Hormone Therapy Given?

Hormone therapy can either be given before or after other adjuvant breast cancer treatments, which may include radiation therapy, immunotherapy, chemotherapy or vaccine therapy. Adjuvant therapy typically begins two to 12 weeks after surgery.

With early stage ER-positive breast cancer, you may receive at least 5 years of adjuvant therapy, which may include hormone therapy. Hormone therapy also may be used to treat breast cancer that has spread to other parts of your body (metastatic).

Clinical trials are under way using hormone therapy to treat breast cancer before surgery. This is done to reduce the size of breast tumors and allow breast-conserving surgery. So far, it has been primarily tested in postmenopausal women.

Trials also are studying whether hormone therapy can be use to prevent breast cancer in high-risk women. Based on these studies, the U.S. Food and Drug Administration (FDA) has approved taxomifen and raloxifene for reducing the risk of breast cancer in high-risk women; raloxifene was approved only for postmenopausal women.

Talk It Over

All hormone therapy may cause side effects, but the effects vary depending on the type of drug and how it is being used. Common side effects are hot flashes, night sweats and vaginal dryness. In premenopausal women, it disrupts menstrual cycles.

There are other less common side effects associated with the various drugs, so be sure to talk with our health care professional about the risks and benefits of each. Whichever course of action your doctor recommends, fighting breast cancer is not easy.

In addition to the physical pain and discomfort, you may experience many emotions, such as guilt, denial, anxiety, fear and helplessness. To avoid becoming overwhelmed, it's important to form a strong network of family and friends who can be available to support you during this time. It can be helpful to talk through what you're feeling so that your concerns don't build up inside your head. You may also choose to talk with a professional therapist for counseling.

As difficult as it may be to undergo intense treatment, remember that many women do successfully beat cancer.

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