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Breast Cancer Basics
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Advanced Breast Cancer
A Guide For Your Partner


Hormone Therapy


What is Hormone Therapy?
Chemotherapy uses cytotoxic drugs to kill cancer cells. By contrast, hormone therapy uses medications that prevent cancer cells from growing by changing normal body processes.

Hormones are natural chemicals produced by the body to regulate various processes such as blood sugar metabolism, bone growth, or milk production in the breasts. Hormones include such substances as adrenaline, insulin, and estrogen.

Certain types of breast cancers need the female hormones estrogen and progesterone to grow. By using chemicals that block the action of these hormones, it is possible to slow down, or even stop, the growth of cancer cells.

How exactly is this done? Some cancers are made of cells equipped with hormone receptor sites scattered over their surface. Hormone molecules fit into these sites like keys into locks, and stimulate the cells to divide. This makes the tumor grow faster. These types of cancers are called estrogen or progesterone receptor positive.

Hormone therapies work by one of three ways. Some hormone therapies, such as the drug tamoxifen, attempt to block the effects of the hormones that the body produces. Individual molecules of these compounds fit into the receptor sites and block them, keeping estrogen and progesterone out. Think of it as the wrong key in a door lock: it fits, but won't turn, and keeps out the right key. The result: the cells are not stimulated, and the tumor stops growing.

Others, such as drugs called aromatase inhibitors, keep the body from producing the hormones in the first place. Aromatase is a natural enzyme that helps produce estrogen in the woman's body. Inhibiting this enzyme can be a very effective way of reducing estrogen. Femara, Arimidex, and Aromasin are some of the aromatase inhibitors currently approved by the FDA. Estrogen and progesterone production can also be inhibited by surgically removing the ovaries.

Yet other, newer, compounds (for example, Faslodex) work by eliminating the hormone receptors on the surface of the cells, making the cells insensitive to the growth-enhancing effect of hormones.

Do not confuse hormone therapy for treatment of breast cancer, with hormone replacement therapy, or HRT, for management of hot flashes and other symptoms during menopause. Different drugs, different goals.

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How Hormone Therapy is Given
As with chemotherapy, your hormone therapy should be supervised by a medical oncologist—a board-certified specialist, trained in treating cancer with drugs.

Hormone therapy is generally given in the form of a pill, although some, such as Faslodex are given as an intramuscular injection.


Do You Need Hormone Therapy?
Cancer that is confined to the breast area can be treated effectively with surgery and radiation therapy. Cancer that has spread to areas beyond the breast is much more difficult to treat. Unfortunately, it is not always possible to determine with certainty at the time of diagnosis whether the cancer has spread or not.

Because of this, many clinicians recommend treatment with adjuvant, or additional therapy such as chemotherapy or hormonal therapy, or both, whenever there is a reasonable chance that cancer cells have metastasized to other parts of the body. The reasoning is that while hormone therapy and chemotherapy may be unpleasant, cancer recurrences can be life-threatening. Therefore the benefits outweigh the side effects.

Not all types of breast cancer can be treated with hormone therapy. To determine if hormone therapy is right for you, a sample of your tumor will be sent to a special lab, where it will be tested for estrogen receptors and progesterone receptors. If the tests show that your tumor is estrogen receptor positive (ER+) or progesterone receptor positive (PR+), it means that the tumor can be stimulated by these hormones. In this case, your medical oncologist may recommend hormone therapy. If the tests are negative, hormone therapy will have no effect on the growth of your cancer, regardless of your age.

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Side Effects of Hormone Therapy
The side effects of hormone therapy vary with the type of therapy used. In general, hormone therapy has far fewer, and less severe, side effects than chemotherapy.

Because hormone therapy blocks estrogen, it may cause the same symptoms as going through menopause, including hot flashes, changes in menstrual periods and vaginal dryness.

Hormone therapy may affect the rate of loss of calcium from bones, which may lead to osteoporosis. Ask your physician if you need to have a simple test called bone densitometry to determine whether your bones are in danger of becoming too brittle.

While you are on hormone therapy, you may still get pregnant, even if your periods have stopped as a result of the treatment. Since hormone therapy may be harmful to the fetus, it's important to use birth control if you are sexually active. Do not use an oral contraceptive, or an injection or implant that contains hormones, since they may interfere with your hormone therapy. Instead, use a barrier method, such as a condom or a diaphragm.

Feel free to discuss with your doctor or nurse any sexual difficulties that you may be experiencing due to hormone therapy. Remember, there are many ways of helping you maintain your sexual activity even while you are being treated. In Chapter 13 we will review the sexual side effects of cancer therapy in greater detail.


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