Breast Cancer: Hormone Therapy Overview

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Breast Cancer: Hormone Therapy Overview

There are certain hormones that can attach to cancer cells and can affect their ability to multiply. The purpose of hormone therapy -- also called hormonal therapy or hormone treatment -- is to add, block or remove hormones.

With breast cancer, the female hormones estrogen and progesterone can promote the growth of some breast cancer cells. So in these patients, hormone therapy is given to block the body's naturally occurring estrogen and fight the cancer's growth.

There are two types of hormone therapy for breast cancer.

Drugs that inhibit estrogen and progesterone from promoting breast cancer cell growth.
Drugs or surgery to turn off the production of hormones from the ovaries.
Do not confuse the term hormone therapy that is used for treating breast cancer patients with hormone replacement therapy that is typically used by post-menopausal women. Hormone therapy for cancer treatment stops hormones from getting to cancer cells. Hormone therapy for post-menopausal women without cancer (in the past called "hormone replacement therapy") adds more hormones to your body to counter the effects of menopause.

Who Gets Hormone Therapy for Cancer?
As part of the diagnosis process, tests are done to determine if the cancer cells have estrogen or progesterone receptors. If so, that means that growth of the cancer can be stimulated with these hormones. If a cancer is found to have these receptors, hormone therapy is recommended as part of the treatment plan.

What Drugs Are Used?
There are several common hormone therapy drugs used for breast cancer:

Tamoxifen
Fareston
Arimidex
Aromasin
Femara
Zoladex
Tamoxifen
Tamoxifen (marketed as Nolvadex) is a pill that has been used for 25 years to treat breast cancer. Tamoxifen decreases the chance that some early-stage breast cancers will recur and can prevent the development of cancer in the unaffected breast. Tamoxifen also slows or stops the growth of cancer cells present in the body.

In addition, tamoxifen may offer an alternative to watchful waiting or prophylactic (preventative) mastectomy to women at high risk for developing breast cancer.

Tamoxifen is a type of drug called a selective estrogen-receptor modulator (SERM). At the breast, it' functions as an anti-estrogen. Estrogen promotes the growth of breast cancer cells and tamoxifen blocks estrogen from attaching to estrogen receptors on these cells. By doing this, it is believed that the growth of the breast cancer cells will be halted.

Tamoxifen is often given along with chemotherapy and other breast cancer treatments. It is considered an option in the following cases:

Treatment of ductal carcinoma in situ (DCIS) along with breast-sparing surgery or mastectomy.
Adjuvant treatment of lobular carcinoma in situ (LCIS) to reduce the risk of developing more advanced breast cancer.
Adjuvant treatment of metastatic breast cancer in men and women whose cancers are estrogen-receptor positive.
Treatment of recurrent breast cancer.
To prevent breast cancer in women at high risk for developing breast cancer.
Tamoxifen continued...
Women who should definitely not use tamoxifen include pregnant women, women planning to become pregnant, men or women with a history of blood clots or stroke or those who are taking anticoagulants. Talk to your doctor to see if tamoxifen is right for you.

For women, the side effects of tamoxifen are similar to some of the symptoms of menopause. Two of the most common side effects are hot flashes and vaginal discharge. Other side effects in women may include:

Vaginal dryness and/or itching
Irregular menstrual periods
Headache
Nausea and/or vomiting
Skin rash
Fatigue
Fluid retention and/or weight gain
While some of its side effects are similar to menopausal symptoms, tamoxifen does not cause a woman to begin menopause.

Side effects in men may include:

Headache
Nausea and/or vomiting
Skin rash
Sexual side effects: impotence or decrease in sexual interest
Are There Risks to Taking Tamoxifen?
Yes. These include:

Fertility. Tamoxifen may affect fertility, so it is important to use some form of birth control while you are taking this medication. However, do not use oral contraceptives (the "pill") since they may change the effects of tamoxifen. Tell your doctor right away if you think you may have become pregnant while taking this medication.
Increased blood clots. Women taking tamoxifen may have a slightly increased risk of developing blood clots in the lungs or large veins. This may be especially true for women undergoing chemotherapy (anti-cancer drugs) while taking tamoxifen.
Increased risk of stroke.
Uterine cancer. Tamoxifen may increase a woman's risk of developing uterine cancer (cancer of the lining of the uterus). However, this risk is very small , and needs to be balanced against the significant benefits for the breast.
Cataracts. Taking tamoxifen appears to put some women at increased risk for developing cataracts, a clouding of the lens inside the eye. People have also reported eye problems such as corneal scarring or retinal changes.
A Word About Tamoxifen and Breast Cancer Prevention
In 1998, the National Cancer Institute funded a large study designed to determine whether tamoxifen would reduce the occurrence of breast cancer in healthy women known to be at high risk. The results of the trial showed a 50% reduction in both invasive and non-invasive breast cancer in the treated women.

Tamoxifen has also been shown to substantially reduce the risk of developing invasive breast cancer in women who have had ductal carcinoma in situ (DCIS).

Are There Other Medications That Can Prevent Breast Cancer?
Although research is limited, it has been suggested that another SERM drug, Evista, used to prevent osteoporosis, is similar to tamoxifen and may be able to prevent breast cancer in high risk women. Currently, the FDA has only approved the use of Evista to prevent osteoporosis. A study (known as STAR) is currently underway to see how tamoxifen and Evista compare in preventing breast cancer.

Fareston is another SERM. Like tamoxifen, it blocks certain effects of estrogen and is used as a treatment for advanced breast cancer in postmenopausal women.

Breast Cancer: Hormone Therapy Overview
(continued)
Other Hormone Therapies: Arimidex and Femara and Aromasin
Aromatase inhibitors block the effect of an enzyme that helps the body produce the hormone estrogen. They include Arimidex and Femara.

Another drug, Aromasin (exemestane), is similar to the aromatase inhibitors but is an aromatase inactivator. Instead of blocking the aromatase enzyme, aromatase inactivators actually destroy it.

Aromatase inhibitors delay the progression of breast cancer longer than tamoxifen in women with advanced breast cancer whose tumors rely on estrogen to grow. Specifically, Femara and Arimidex are used as part of the initial or follow-up treatment of hormone-sensitive breast cancer (even those that have spread to other parts of the body) in women who have gone through menopause. They are pills that are taken once a day.

Aromasin is currently used to treat postmenopausal women with breast cancer that has spread outside of the breast that was not responsive to tamoxifen. It's a pill taken once a day after meals.

Side effects include:

Nausea
Fluid retention and/or weight gain
Headache
Zoladex
Zoladex is a drug that stops the production of estrogen. It is used in premenopausal women for the treatment of estrogen sensitive breast cancer.

Side effects include:

Bone thinning which can lead to osteoporosis
Hot flashes
Irregular menstrual periods
Reviewed by Pelin Batur, MD at Cleveland Clinic, March 2006.

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