Hormone Therapy for Breast Cancer Treatment

Written by Madeline Laguaite
Medically Reviewed by Elmer Huerta, MD, MPH on May 14, 2025

Hormones in your body — estrogen and progesterone — can be 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 to treat the cancer.

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 these hormones

 

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. These receptors use estrogen or progesterone. If your cancer does have these receptors, it means it depends on these hormones to grow. In that case, your doctor will probably recommend hormone therapy as part of your treatment plan.

If you’ve already been treated for breast cancer, you might use hormone therapy to help keep it from coming back. It also helps lower your odds of getting new cancers in the other breast.

Also, if you don’t have cancer but have a family history of it — or genes that raise your risk — your doctor may recommend hormone therapy to lower your chances of getting it.

 Hormone therapy drugs for breast cancer treatment include:

Tamoxifen is a pill that doctors have prescribed for more than 50 years to treat breast cancer. It was approved for the treatment of metastatic breast cancer in 1977 and in 1998 for the prevention of recurrence. It works by keeping 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 you’ll get cancer in the other breast later on.

If you’re at high risk for breast cancer, you can take tamoxifen to try to lower your chances of getting it. It’s an alternative to watchful waiting or having surgery to remove a breast (called a mastectomy) before you get breast cancer.

Tamoxifen is an option for treatment of:

  • The earliest form of breast cancer, ductal carcinoma in situ (DCIS), along with surgery
  • Abnormal cells in the glands that make milk, called lobular carcinoma in situ (LCIS), to lessen the chance that they’ll become more advanced breast cancer
  • Breast cancer in men and women whose cancers use estrogen
  • Breast cancer that has spread to other parts of the body or that comes back after treatment

Some people shouldn’t use tamoxifen, such as:

  • Pregnant women
  • Women planning to get pregnant
  • Men or women who’ve had blood clots or a stroke

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 may include:

  • Vaginal dryness or itching
  • Irregular periods
  • Headache
  • Nausea and vomiting
  • Skin rash
  • Fatigue
  • Water retention and weight gain

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

For men, tamoxifen can cause:

  • Headache
  • Nausea and vomiting
  • Skin rash
  • Sexual side effects like erectile dysfunction or a lower sex drive

Yes. The risks include stroke, among others:

Fertility. Tamoxifen can increase your fertility for a short time. But it might harm a growing baby, so it’s important to use some form of barrier birth control while you’re taking it, like condoms or a diaphragm. Don’t use birth control pills. They can 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.

Uterine cancer or sarcoma. The drug may make a woman more likely to get these diseases. But this risk is 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 give some women a higher chance of having this condition, which 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.

A large study by the National Cancer Institute looked at whether tamoxifen lowered cases of breast cancer in healthy women who were known to be likely to get 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 lessens the risk of breast cancer returning in women who have had the earliest form of the disease, ductal carcinoma in situ (DCIS).

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.

Here are some other hormone therapies to know.

Aromatase inhibitors 

This type of hormone therapy drug keeps your body from breaking down testosterone into estrogen. They include:

Aromatase inhibitors keep breast cancer from getting worse for longer than tamoxifen in women who have the 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’re pills that you take once a day. Research has shown that postmenopausal women with early breast cancer have a lower risk of recurrence and a higher survival rate than those treated with tamoxifen alone.

Side effects of aromatase inhibitors include:

  • Nausea and vomiting
  • Diarrhea and constipation
  • Hot flashes
  • Headache
  • Bone pain
  • Severe fatigue
  • Skin rash
  • Swelling and water retention
  • Flu-like symptoms
  • Increased bone loss

Fulvestrant (Faslodex)

This is a shot that keeps estrogen from attaching to cancer cells. Common side effects include:

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

Elacestrant (Orserdu)

This is an orally available selective estrogen receptor degrader (SERD). SERDs are a new class of compounds capable of reducing the estrogen receptor alpha protein level and blocking ER activity.

Imlunestrant (Inluriyo)

Imlunestrant (Inluriyo) is another SERD option. It’s a pill you’ll take once a day. It may be an option if you have advanced or metastatic breast cancer that’s ER-positive, HER2-negative, and ESR1-mutated.

The FDA also approved imlunestrant with abemaciclib (Verzenio) for adults with ER-positive, HER2-negative breast cancer that is advanced or has spread to other parts of the body. This combination is an option if the cancer grew or got worse after at least one hormone therapy and an FDA-authorized test confirms a change (mutation) in the ESR1 gene.

Vepdegestrant (Veppanu)

A new targeted therapy, vepdegestrant (Veppanu) is the first FDA-approved proteolysis targeting chimera (PROTAC), a targeted protein degrader taken once daily with food for people with ER+, HER2-, ESR)-mutated advanced or metastatic breast cancer, whose disease has progressed after at least one prior hormone (endocrine) therapy. An FDA-authorized test confirming ESR1 mutation must be given before starting treatment. 

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