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:
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
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.
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
There are three main types of hormonal therapy medicines used to treat breast cancer:
selective estrogen receptor modulators (SERMs)
estrogen receptor downregulators (ERDs)
Aromatase inhibitors work by blocking the enzyme aromatase, which turns the hormone androgen into small amounts of estrogen in the body. Aromatase inhibitors can’t stop the ovaries from making estrogen, so these medicines are mainly used to treat post-menopausal women because their ovaries aren’t working anymore. Before menopause, most of the estrogen in your body is made by the ovaries. Still, research is looking to see if aromatase inhibitors can be used to treat pre-menopausal women diagnosed with hormone receptor-positive breast cancer if the women also take ovarian suppression medicine to stop their ovaries from functioning.
There are three aromatase inhibitors used to treat breast cancer:
Arimidex (chemical name: anastrozole)
Aromasin (chemical name: exemestane)
Femara (chemical name: letrozole)
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.
Cells in other tissues in the body, such as bones and the uterus, also have estrogen receptors. But each estrogen receptor has a slightly different structure, depending on the kind of cell it is in. So breast cell estrogen receptors are different from bone cell estrogen receptors and both of those estrogen receptors are different from uterine estrogen receptors. As their name says, SERMs are "selective." This means that a SERM that blocks estrogen's action in breast cells can activate estrogen's action in other cells, such as bone, liver, and uterine cells.
SERMs can be used to treat both pre- and post-menopausal women, as well as men. There are three SERMs:
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)
Estrogen receptor downregulators (ERDs), much like SERMs, block the effects of estrogen on breast cancer cells by sitting in the estrogen receptors. ERDs also lower the number of estrogen receptors and change the shape of breast cell estrogen receptors so they don’t work as well. There is one ERD used to treat breast cancer:
Faslodex (chemical name: fulvestrant)
Adjuvant hormonal therapy treatment time
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
In pre-menopausal women, most of the estrogen in the body is made by the ovaries. In some cases, medicine may be used to stop the ovaries from functioning temporarily, called ovarian suppression or ovarian shutdown. Two medicines commonly used are:
These medicines are given as injections once a month for several months or every few months. They can be used alone or in combination with other hormonal therapy medicines to treat pre-menopausal women.
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. Learn more about Prophylactic Ovary Removal.
— Last updated on June 29, 2022, 3:15 PM