Fulvestrant
- Medical Review: Claire Smith, MD
Fulvestrant (Faslodex) is an injectable hormonal therapy (also known as endocrine therapy) used to treat advanced or metastatic breast cancer that is hormone receptor-positive and HER2-negative
Fulvestrant is part of a class of medicines called selective estrogen receptor degraders (SERDs). These medicines stop estrogen from helping breast cancer cells to grow.
In 2002, fulvestrant became the first SERD to be approved by the Food and Drug Administration (FDA) as a treatment for breast cancer. It is given by injection.
Since then, the FDA has approved two more SERDs, available in pill form, to treat hormone receptor-positive, HER2-negative metastatic breast cancer that tests positive for a mutation in a gene called ESR1:
- Elacestrant (Orserdu) was approved in 2023.
- Imlunestrant (Inluriyo) was approved in 2025.
How fulvestrant works
Fulvestrant attaches to the estrogen receptors on hormone receptor-positive breast cancer cells. This blocks estrogen’s ability to attach to the estrogen receptor and can stop cancer cells from growing.
Fulvestrant is often referred to as a selective estrogen receptor degrader (SERD), which means fulvestrant can break down or weaken the estrogen receptor, making it inactive.
Who gets fulvestrant
Fulvestrant can be given to adults with hormone receptor-positive advanced or metastatic breast cancer.
Fulvestrant and menopausal status
Fulvestrant is FDA approved for use in postmenopausal women with advanced or metastatic hormone receptor-positive breast cancer. Women taking fulvestrant may have gone through menopause naturally or because they chose to have their ovaries removed to reduce ovarian and breast cancer risk.
Fulvestrant can also be given to premenopausal women with advanced or metastatic hormone receptor-positive breast cancer who are taking medicines that stop the ovaries from producing estrogen. These medicines are called gonadotropin-releasing hormone (GnRH) agonists (also may be referred to as luteinizing hormone-releasing hormone agonists).
Fulvestrant in hormone receptor-positive, HER2-negative breast cancer
For women with hormone receptor-positive advanced or metastatic breast cancer that is also HER2-negative, fulvestrant can be used:
- If the cancer returns while taking an aromatase inhibitor for early stage breast cancer. In this situation, fulvestrant would commonly be given with a targeted therapy called a CDK4/6 inhibitor.
- If the cancer progresses (keeps growing) after receiving another type of hormonal therapy. The most common time fulvestrant would be given would be after cancer grows while taking an aromatase inhibitor and CDK4/6 inhibitor. Fulvestrant may be given alone or in combination with other targeted therapies.
The FDA-approved CDK 4/6 inhibitors are:
Fulvestrant also may be used to treat hormone receptor-positive, HER2-negative advanced or metastatic breast cancers found to have mutations in genes such as PIK3CA, AKT1, or PTEN. Biomarker testing can confirm each of these mutations. Depending on the mutation, fulvestrant can be given along with targeted treatments such as:
- Inavolisib (Itovebi) and palbociclib
- Alpelisib (Piqray)
- Capivasertib (Truqap)
Fulvestrant in hormone receptor-positive, HER2-positive breast cancer
For women with hormone receptor-positive breast cancer that is HER2-positive, fulvestrant can be used along with trastuzumab (Herceptin), a HER2-targeted therapy. Some people may take abemaciclib as well.
Fulvestrant in male breast cancer
Men with advanced or metastatic hormone receptor-positive, HER2-negative breast cancer are also eligible for treatment with fulvestrant.
How fulvestrant is given
Fulvestrant is given by injection into the buttocks. For the first month, you will receive two injections every 2 weeks at your doctor’s office. After the first month, fulvestrant is given as two injections every 4 weeks.
The standard fulvestrant dose is 500 milligrams (mg). For people with liver problems, the dose may be lowered to 250 mg per treatment. That’s because the liver breaks down fulvestrant.
Side effects and things to remember
Common side effects of fulvestrant are:
- Pain at the site you receive the injection
- Hot flashes, a common symptom of menopause
- Nausea and vomiting
- Fatigue
- Muscle, bone, and joint pain
- Headache
- Loss of appetite
- Weakness
- Cough
- Constipation
- Shortness of breath
- Higher liver enzymes, which means damage or inflammation of the liver
Fulvestrant can harm an unborn baby. You should not take fulvestrant if you’re pregnant. You also shouldn’t get pregnant while taking it and for a year after treatment ends.
Women should avoid breastfeeding while taking fulvestrant.
Tell your healthcare team if you:
- Have liver problems
- Have low levels of platelets in your blood
- Bleed easily (fulvestrant is given by injection into the muscle, so your team should be aware of any bleeding issues)
Stay connected
Sign up to receive emotional support, medical insight, personal stories, and more, delivered to your inbox weekly.
Living Beyond Breast Cancer is a national nonprofit organization that seeks to create a world that understands there is more than one way to have breast cancer. To fulfill its mission of providing trusted information and a community of support to those impacted by the disease, Living Beyond Breast Cancer offers on-demand emotional, practical, and evidence-based content. For over 30 years, the organization has remained committed to creating a culture of acceptance — where sharing the diversity of the lived experience of breast cancer fosters self-advocacy and hope. For more information, learn more about our programs and services.