Hormone therapy for breast cancer stops or slows the growth of hormone-sensitive tumors. Some types of therapy lower estrogen levels. Others prevent estrogen from acting on breast cancer cells.

Sometimes doctors use hormone therapy in addition to primary treatments for early-stage breast cancer. They may use it to treat advanced cancer or reduce the size of a tumor before surgery. In addition, they use it as a preventive measure for females with a high risk of breast cancer.

Breast cancer is the second most common cancer in females in the United States. Yet not all breast cancer tumors are hormone-sensitive. According to the American Cancer Society, about 2 of every 3 cases fall into this category.

Keep reading to learn more about the types and side effects of hormone therapy, what to expect during treatment, and the outlook.

A person thanking their doctor after successful hormone therapy for their breast cancer.Share on Pinterest
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Another term for hormone therapy is endocrine therapy. It is not the same thing as hormone replacement therapy, which relieves symptoms of menopause.

If estrogen and progesterone can affect breast cancer cells, the tumor is called hormone dependent or hormone sensitive. This means the cells have hormone receptor proteins that become activated when the hormones connect to them.

A tumor with estrogen receptors is called estrogen receptor positive, and a tumor that has progesterone receptors is called progesterone receptor positive. When the hormones activate these receptors, changes occur in certain genes, increasing cell growth.

To reduce this activation, hormone therapy blocks the body’s ability to produce the hormones. It can also hinder the effects of hormones on breast cancer cells.

Doctors categorize the types of hormone therapy based on the method by which they work. Here are some details:

Block ovarian function

Ovaries are a female’s main source of hormones, so suppressing ovarian function reduces the production of estrogen. Doctors can do this by surgically removing the ovaries, which is a permanent measure.

They can also temporarily suppress ovarian function with medications called gonadotropin-releasing hormone agonists. These suppress signals that stimulate the ovaries to make estrogen. An example is goserelin (Zoladex).

Block estrogen production

Aromatase inhibitors are medications that block an enzyme the body uses to make estrogen. Doctors mainly use these in postmenopausal females because the ovaries in premenopausal females produce too much of the enzyme to effectively block. An example is anastrozole (Arimidex).

Block estrogen’s effects

These medications interfere with estrogen’s ability to stimulate the growth of a breast tumor. Selective estrogen receptor modulators (SERMs) bind to estrogen receptors, which prevents estrogen from binding with cells.

SERMs also mimic estrogen, so while they block estrogen’s effects on breast tissue, they mimic its effects on bone and uterine tissue. Examples include tamoxifen (Nolvadex) and raloxifene (Evista).

Other drugs block estrogen in a different way. An example is fulvestrant (Faslodex), a medication that binds to the estrogen receptor, blocking estrogen. Unlike SERMS, these drugs do not mimic estrogen.

All hormone therapy for breast cancer deprives the body of the positive effects of estrogen. In addition, each class of drugs has less common side effects.

Most common

The most common side effects include:

  • night sweats
  • hot flashes
  • vaginal dryness
  • menstrual cycle disruptions in premenopausal females

Less common

These less common side effects are serious, and they differ with the medication or intervention.

Ovarian suppression

Side effects of ovarian suppression include:

  • mood swings
  • depression
  • bone loss
  • loss of libido, or sex drive

Aromatase inhibitors

Side effects of aromatase inhibitors include:

  • risk of heart attack, heart failure, abnormal cholesterol levels, and chest pain
  • mood swings
  • depression
  • bone loss
  • joint pain

Tamoxifen (Nolvadex)

Side effects of tamoxifen in females include:

  • risk of blood clots, especially in the legs and lungs
  • endometrial and uterine cancer
  • stroke
  • bone loss in premenopausal women
  • cataracts
  • mood swings

Side effects of tamoxifen in males includes:

  • nausea
  • vomiting
  • headaches
  • loss of libido
  • impotence
  • rash

Raloxifene (Evista)

Side effects of raloxifene include:

  • certain types of strokes
  • risk of blood clots, particularly in the legs and lungs


Side effects of fulvestrant include:

  • tiredness and weakness
  • gastrointestinal symptoms, such as constipation, nausea, and vomiting
  • pain in parts of the body, including the back, bones, and joints
  • loss of appetite
  • headaches
  • breathing problems, such as shortness of breath, cough, and painful breathing

All the medications for hormone therapy are pills that a person takes once a day, with two exceptions.

One is fulvestrant (Faslodex), which a person usually gets in the form of an injection. Another is Soltamox, a liquid form of tamoxifen that people take by mouth.

A person will usually receive hormone therapy for 5 –10 years. The duration depends on several factors, such as side effects and the stage of cancer.

According to the National Cancer Institute (NCI), the 5-year survival rate for all breast cancer in females is 90.3%. The rate for those with hormone-sensitive cancer is a little higher than for those who do not have this type of cancer.

Males have a slightly lower 5-year survival rate. The Centers for Disease Control and Prevention (CDC) note that from 2007–2016, the rate was 84.7%.

Hormone therapy plays a role in these high 5-year survival rates. A 2017 study reviewed clinical trials involving the use of hormone therapy for breast cancer. The authors conclude that medications such as tamoxifen have significantly reduced cancer deaths. Additionally, aromatase inhibitors such as anastrozole have further improved breast cancer survival.

Research from 2019 shows that the duration of hormone therapy can impact survival rates. The authors analyzed data from 2,002 people newly diagnosed with breast cancer between 2000–2005. They conducted follow-ups until 2013 and found that individuals who took the therapy for less than 2 years had the lowest survival rates. Extending the duration of the therapy is vitally important for increasing survival, they concluded.

The CDC warn that many alternative therapies for breast cancer have not undergone enough research to prove their safety. Before a person starts an alternative treatment, they should talk with their doctor.

However, a 2018 study that reviewed research on the topic suggests that several natural compounds hold promise. Despite the findings, the authors recommend further studies.

The findings are as follows:

  • Cruciferous vegetable compound: Rodent studies show that cruciferous vegetables, such as cabbage, broccoli, and cauliflower, contain a compound that may inhibit tumors. However, an older 2014 study suggests that certain concentrations of the compound may have the opposite effect.
  • Curcumin: This compound is the active ingredient in the spice turmeric, which research shows may help fight breast cancer. Although it is one of the agents that holds the most promise, the authors note that it has poor bioavailability, which means the body does not absorb it well.
  • Green tea compound: Research suggests that a compound in green tea called epigallocatechin gallate (EGCG) may be beneficial for breast cancer. The downside is that EGCG may interact with some anticancer drugs in an undesirable way.

When prescribing hormone therapy for breast cancer, doctors have an array of medications and interventions from which to choose. Because estrogen causes some breast cancers to grow faster, the aim of the therapy is to either reduce estrogen or block a person’s response to it.

Hormone therapy has side effects and risks, but one study suggests that it can significantly reduce the number of deaths from the disease and future recurrences of breast cancer.

Preliminary research indicates that some natural compounds, such as curcumin, may help with breast cancer. Despite the encouraging results, researchers need to conduct more studies to determine their safety and effectiveness.