Hormonal Therapy for Breast Cancer
Hormonal therapy, also called anti-estrogen therapy, endocrine therapy, or hormone therapy, is used to treat all stages of hormone receptor-positive breast cancer.
Hormone receptor-positive breast cancer is breast cancer that has:
estrogen receptors
progesterone receptors
both estrogen and progesterone receptors
When either estrogen or progesterone attaches to a receptor on a hormone receptor-positive breast cancer cell, it tells the cell to grow and multiply.
According to the American Cancer Society, about 66% of all breast cancers are hormone receptor-positive.
When is hormonal therapy used for breast cancer?
Hormonal therapy medicines are used in four ways:
To shrink the cancer before surgery: If the breast cancer is large and hormone receptor-positive, your doctor may recommend hormonal therapy before surgery to shrink the cancer. Treatments given before surgery are called neoadjuvant treatments, so hormonal therapy given this way is called neoadjuvant hormonal therapy.
To reduce recurrence risk: If you’ve been diagnosed with early-stage hormone receptor-positive breast cancer, your treatment plan will include hormonal therapy after surgery and possibly other treatments to reduce the risk of the cancer coming back (recurrence). Treatments given after surgery are called adjuvant treatments, so hormonal therapy given this way is called adjuvant hormonal therapy.
To stop advanced-stage cancer from growing: If you’ve been diagnosed with advanced-stage, hormone receptor-positive breast cancer, hormonal therapy can be used to help stop the cancer from growing.
To reduce the risk of a first diagnosis: Hormonal therapy also can be used to reduce breast cancer risk in certain women who haven’t been diagnosed. Women with a much higher than average risk of breast cancer may take a hormonal therapy medicine preventively to reduce the risk of hormone receptor-positive breast cancer developing.
How does hormonal therapy treat breast cancer?
Hormonal therapy medicines work in two ways:
by blocking estrogen production in the body
by blocking the effects of estrogen on breast cancer cells
Hormonal therapy is not a treatment option for hormone receptor-negative breast cancer.
It's important to know that hormonal therapy for breast cancer is different than hormone replacement therapy (HRT) for treating symptoms of menopause. HRT isn't used to treat breast cancer. HRT is taken by some women to treat troublesome menopausal side effects such as hot flashes and mood swings. HRT is used to raise estrogen levels that drop after menopause. HRT contains estrogen and can contain progesterone and other hormones. Hormonal therapy for breast cancer is exactly the opposite — it blocks or lowers estrogen levels in the body.
Types of hormonal therapy to treat breast cancer
There are three main types of hormonal therapy medicines used to treat breast cancer:
Aromatase inhibitors stop the body from making estrogen.
Selective estrogen receptor modulators (SERMs) block the action of estrogen on certain cells.
Selective estrogen receptor downregulators (SERDs) block the action of estrogen on certain cells.
Aromatase inhibitors lower estrogen levels by stopping the enzyme aromatase from changing other hormones into estrogen. In estrogen receptor-positive breast cancer, the hormone estrogen can stimulate the growth of breast cancer cells.
There are three aromatase inhibitors used to treat breast cancer:
Arimidex (chemical name: anastrozole)
Aromasin (chemical name: exemestane)
Femara (chemical name: letrozole)
Learn more about aromatase inhibitors.
Selective estrogen receptor modulators (SERMs) block the effects of estrogen on breast cancer cells by sitting in the estrogen receptors. If a SERM is in the estrogen receptor, estrogen can’t attach to the cancer cell and the cell doesn’t receive estrogen’s signals to grow and multiply.
There are three SERMs used to treat breast cancer:
tamoxifen in pill form, also called tamoxifen citrate (brand name Nolvadex), and in liquid form (brand name: Soltamox)
Evista (chemical name: raloxifene)
Fareston (chemical name: toremifene)
Learn more about selective estrogen receptor modulators (SERMS).
Selective estrogen receptor downregulators (SERDs) also block the effects of estrogen on breast cancer cells. SERDs also reduce the amount of estrogen receptors and change their shape so they don’t work as well. There are two SERDs used to treat breast cancer:
Learn more about selective estrogen receptor downregulators (SERDs).
Hormonal therapy side effects
For many people, the side effects of hormonal therapy make sticking with treatment difficult. Studies have shown that lots of people prescribed the medicines either don’t start taking hormonal therapy, skip doses, or stop taking it early. In many cases, this is because of side effects they are experiencing or are afraid of developing.
But it’s important to keep in mind that the side effects from hormonal therapy medicines vary from person to person. Some people have troublesome side effects and others have milder side effects or no trouble tolerating these medicines.
Read more about hormonal therapy side effects.
There are ways to make taking hormonal therapy more manageable, such as medication and lifestyle changes. If you’re struggling with hormonal therapy side effects, talk with your healthcare team about your options.
How long do you take hormonal therapy for breast cancer?
For many years, women took hormonal therapy for five years after surgery for early-stage, hormone receptor-positive breast cancer. In most cases, the standard of care is five years of tamoxifen, or two to three years of tamoxifen followed by two to three years of an aromatase inhibitor, depending on menopausal status.
Recent research has found that in certain cases, taking tamoxifen for 10 years instead of five years after surgery lowered a woman’s risk of recurrence and improved survival.
In most cases, a post-menopausal woman diagnosed with early-stage, hormone receptor-positive breast cancer would take an aromatase inhibitor for five years after surgery to reduce the risk of recurrence. After that, if breast cancer had been found in the lymph nodes, called node-positive disease, a woman would take an aromatase inhibitor for an additional five years, for a total of 10 years of hormonal therapy treatment.
Doctors call taking hormonal therapy for 10 years after surgery extended adjuvant hormonal therapy.
Ovarian suppression or removal
If you’ve been diagnosed with hormone receptor-positive breast cancer and haven’t yet gone through menopause, your doctor may recommend that you take a medicine to stop your ovaries from producing estrogen (also called ovarian suppression, ovary ablation, or ovarian shutdown ).
Two medicines commonly used are:
These medicines can be used alone or in combination with other hormonal therapy medicines to treat people who haven't gone through menopause.
Once you stop receiving the medicine, your ovaries usually begin functioning again. The time it takes for the ovaries to recover varies from woman to woman.
Some women with a much higher than average risk of breast cancer may choose to have their ovaries removed, called prophylactic or preventive ovary removal, either before or after being diagnosed with breast cancer.
— Last updated on July 30, 2025 at 3:51 PM
