Breast Cancer and Hormone Therapy

Hormones that every woman has in her body -- estrogen and progesterone -- can serve as fuel for some types of breast cancer. They help the cells grow and spread. Hormone therapy, also called endocrine therapy, adds, blocks, or removes those chemicals to treat the disease.

There are two types of hormone therapy for breast cancer:

  • Drugs that stop estrogen and progesterone from helping breast cancer cells grow.
  • Drugs or surgery to keep the ovaries from making the hormones.

Hormone therapy is different from hormone replacement therapy (HRT), a treatment that adds hormones to the body to counter the effects of menopause.

Who Gets Hormone Therapy for Breast Cancer?

When you’re diagnosed with breast cancer, your doctor will test cells from your tumor to see if they have parts on their surfaces called receptors that use estrogen or progesterone. If they do, it means that they depend on these hormones to grow. In that case, your doctor will probably recommend hormone therapy as part of your treatment plan.

Hormone Therapy Drugs for Breast Cancer

Common hormone therapy drugs for breast cancer treatment include:

Breast Cancer and Tamoxifen

Tamoxifen is a pill that doctors have prescribed for more than 30 years to treat breast cancer. It works by blocking estrogen from attaching to the cancer cells.

Doctors first used tamoxifen to treat women whose breast cancer had spread in their bodies because it slowed or stopped the growth of the disease. The drug also lowers the chance that some early-stage breast cancers will come back. And it can lower the risk that a woman will get cancer in her other breast later on.

Women who are at high risk for breast cancer can take tamoxifen to try to lower their chances of getting the disease. It’s an alternative to watchful waiting or having surgery to remove a breast, called a mastectomy, before they get the disease.

Tamoxifen is an option for:

  1. Treatment of the earliest form of breast cancer, ductal carcinoma in situ (DCIS), along with surgery.
  2. Treatment of abnormal cells in the glands that make milk, called lobular carcinoma in situ (LCIS), to reduce the risk that they’ll become more advanced breast cancer.
  3. Treatment of breast cancer in men and women whose cancers use estrogen.
  4. Treatment of breast cancer that has spread to other parts of the body or that comes back after treatment.
  5. To prevent breast cancer in women at high risk for the disease.

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Some people should not use tamoxifen:

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 ones are hot flashes and vaginal discharge. Other problems for women may include:

The side effects may be similar to menopause, but tamoxifen doesn’t trigger menopause.

For men, tamoxifen can cause:

Are There Risks to Taking Tamoxifen?

Yes. The risks include:

  • Fertility. Tamoxifen can increase a woman’s fertility for a short time. But it might be harmful to a growing baby, so it’s important to use some form of barrier birth control while you are taking it, like condoms or a diaphragm. Don’t use birth control pills since they may change how the drug works and affect the breast cancer. Tell your doctor right away if you think you’ve become pregnant while you’re taking tamoxifen.
  • Blood clots. Women who take tamoxifen may have a slightly higher risk of blood clots in their lungs or large veins. It’s an even bigger risk for smokers.
  • Stroke.
  • Uterine cancer or sarcoma. The drug may increase a woman's risk of these diseases. But this risk is very small, and it may be outweighed by the benefits of tamoxifen for breast cancer treatment. Talk to your doctor to know for sure.
  • Cataracts. Tamoxifen seems to put some women at increased risk for this condition that clouds the lens inside the eye. People have also reported eye problems such as corneal scarring or retinal changes.
  • Medications. Tamoxifen may affect how other drugs work in your body.

Tamoxifen and Breast Cancer Prevention

In 1998, the National Cancer Institute did a large study to find out whether tamoxifen lowered cases of breast cancer in healthy women who were known to be at high risk for the disease. The results of the trial showed a 50% reduction in breast cancer in the women who took the drug.

Studies have also shown that tamoxifen reduces the risk of breast cancer in women who have had the earliest form of the disease, ductal carcinoma in situ (DCIS).

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Can Other Drugs Prevent Breast Cancer?

Another drug, raloxifene (Evista), which prevents the bone-thinning disease osteoporosis, is similar to tamoxifen. Studies have found that it prevents breast cancer in women who are at high risk, but with fewer side effects. The FDA has approved it for breast cancer prevention.

Other Hormone Therapies

Aromatase inhibitors are another type of hormone therapy drug. They keep the body from breaking down testosterone into estrogen. They include anastrozole (Arimidex) and letrozole (Femara).

Aromatase inhibitors keep breast cancer from getting worse for longer than tamoxifen in women with advanced disease whose tumors rely on estrogen to grow. For women who have gone through menopause, the drugs can fight cancer even after it has spread to other parts of the body. They are pills that you take once a day.

Side effects of aromatase inhibitors include:

Another drug, exemestane (Aromasin), treats postmenopausal women with breast cancer that has spread outside of the breast. It’s best for people who’ve tried tamoxifen but it didn’t help. It's a pill you take once a day after meals.

Side effects of exemestane include:

  • Nausea
  • Water retention
  • Weight gain
  • Headache
  • Hot flashes

Palbociclib (Ibrance) is not hormone therapy by itself. It's a drug that stops other molecules known to help cancer cells grow. The drug, which doctors give along with letrozole, is for postmenopausal women with advanced cancer who haven’t yet tried hormone therapy.

Side effects of palbociclib include:

  • Low levels of red and white blood cells
  • Fatigue
  • Nausea and vomiting
  • Decreased appetite
  • Mouth sores
  • Upper respiratory infections

Fulvestrant (Faslodex) is an injection that keeps estrogen from attaching to cancer cells. The drug is for postmenopausal women who have HER2 proteins on their cancer cells and have already tried anti-estrogen therapy. Common side effects include:

  • Pain where you get the injection
  • Nausea and vomiting
  • Loss of appetite
  • Weakness and fatigue
  • Hot flashes
  • Cough
  • Muscle, joint, and bone pain
  • Constipation
  • Shortness of breath

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Zoladex and Lupron for Breast Cancer

Goserelin (Zoladex) and leuprorelin (Lupron) are drugs that stop the ovaries from making estrogen. They’re for premenopausal women with breast cancer that uses the hormone to grow.

Side effects of these two drugs include:

  • Water retention
  • Hot flashes
  • Irregular periods
  • Pain at the spot where you get the injection
WebMD Medical Reference Reviewed by Jennifer Robinson, MD on April 10, 2015

Sources

SOURCE: 

American Cancer Society: "Breast Cancer Hormone Therapy."

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