Side Effects of Hormonal Therapy for Breast Cancer
Hormonal therapy (also called anti-estrogen, endocrine, or hormone therapy) is used to treat various stages of hormone receptor-positive breast cancer. This breast cancer uses the hormones estrogen and progesterone to grow.
If you’ve been diagnosed with this type of breast cancer, there’s a good chance that your doctor will recommend you take hormonal therapy. That’s because research shows taking these medicines for 5 to 10 years after the diagnosis of early stage breast cancer lowers the risk that the breast cancer will come back (recurrence).
But there’s a catch: Some people find the side effects of hormonal therapy to be unbearable. Up to half of women who are prescribed hormonal therapy either don’t start the medicine, skip doses, or stop taking it early due to side effects, which include hot flashes, weight gain, mood swings, vaginal dryness, and fatigue.
Understanding why hormonal therapy causes side effects and the steps you can take to relieve these symptoms can help you make the best decision about taking hormonal therapy long term.
Why does hormonal therapy cause side effects?
Most hormonal therapy medicines work by blocking estrogen from attaching to proteins called receptors in cancer cells or reducing the amount of estrogen in the body. Without access to estrogen, breast cancer cells can’t grow.
Non-cancerous cells in your body — including in your brain, bones, uterus, vagina, and heart — also rely on estrogen. Hormonal therapy can interfere with how these healthy cells function, leading to a variety of side effects.
Side effects of hormonal therapy
Everyone’s experience with side effects from medicines can be different. Your age, other health conditions, and menopausal status can all affect how your body responds to hormonal therapy.
While some people have a lot of side effects from taking hormonal therapy, others don’t. For most people, the side effects of the medicines will begin within the first few months of the treatment.
Tamoxifen (brand name: Nolvadex) is one of the most well-known hormonal therapies. It is a type of medicine called a selective estrogen receptor modulator (SERM). Other SERMs include Evista (chemical name: raloxifene) and Fareston (chemical name: toremifene).
Common tamoxifen side effects include hot flashes, vaginal discharge or dryness, loss of libido, fatigue, and depression. Less common, but more serious side effects of tamoxifen include endometrial cancer, blood clots, and stroke.
Common Evista side effects include hot flashes, leg cramps, swelling, flu-like symptoms, and joint pain. Less common, but serious side effects of Evista include blood clots and stroke.
Common Fareston side effects include hot flashes, sweating, nausea, and vaginal discharge or dryness. Less common, but serious side effects of Fareston include a fast, slow, or irregular heartbeat and breathing problems.
Arimidex (chemical name: anastrozole), Aromasin (chemical name: exemestane), and Femara (chemical name: letrozole) are what are known as aromatase inhibitors (AIs).
Arimidex, Aromasin, and Femara have similar side effects, including joint and bone pain, hot flashes, vaginal dryness, and high blood pressure. More serious side effects include heart problems and bone loss.
Faslodex (chemical name: fulvestrant) and Orserdu (chemical name: elacestrant) are both medicines called selective estrogen receptor downregulators (SERDs). These medicines are only prescribed for advanced-stage or stage IV breast cancer.
Common Faslodex side effects include injection site pain, nausea, bone and muscle pain, hot flashes, and headache. In rare cases, Faslodex can also cause bleeding problems.
Common Orserdu side effects include nausea, fatigue, vomiting, joint pain, and loss of appetite. Less common, but severe side effects include heart attack and stroke.
If you have other health conditions, you may face worse symptoms when taking hormonal therapy medicines. For example, if you have arthritis, your joint aches may become worse. If you’re middle-aged or older and have already been experiencing symptoms of perimenopause or menopause, your symptoms might become more severe when you start taking hormonal therapy.
Younger women who haven’t gone through menopause and are prescribed hormonal therapy face unique challenges, as well, including having to deal with menopausal symptoms like vaginal dryness and hot flashes at a much younger age than they normally would. Hormonal therapy can also affect fertility and plans to have children, as you cannot take these medications while pregnant or trying to get pregnant. (That said, research suggests that pausing hormonal therapy to get pregnant is safe and does not affect your risk of recurrence. Longer follow-up studies are needed to confirm these findings.)
Managing side effects of hormonal therapy
The side effects of hormonal therapy can be painful, difficult, and annoying, but these medicines can keep hormone receptor-positive breast cancer from coming back.
This doesn’t mean you need to suffer in silence, though. Use a symptom tracker or jot down any symptoms you have once you start taking the medicine, including the days and time of day you experience them.
Don’t wait for symptoms to become severe — talk to your healthcare team about these symptoms as you notice them.
Avoid hot flash triggers such as stress, cigarettes, alcohol, caffeine, diet pills, spicy food, hot food or drink, hot tubs, saunas, hot showers, hot rooms, and hot weather.
Reduce the fat in your diet. Over time, a low-fat diet helps some people with hot flashes.
Dress in loose and airy fabrics such as cotton, linen, and rayon.
Keep ice water nearby so you can sip it to cool down. Pack a small cooler full of cold water to carry with you.
Take a cool shower before going to bed.
Consider natural remedies. Techniques that may help include meditation, massage, yoga, and acupuncture.
Ask your doctor about medications. There are several prescription medications for hot flashes.
Learn more about hot flashes, including why they happen and how long they last.
Try over-the-counter pain medications. Naproxen and ibuprofen may help you manage bone and joint pain.
Consider complementary and holistic therapies. Acupuncture, chiropractic therapy, massage, music therapy, and hypnosis have been shown to reduce pain.
Use hot or cold packs, or a combination of the two, to soothe sore areas. Heat can help reduce muscle spasms and cold can help reduce inflammation.
Eat a healthy diet that includes enough calcium and vitamin D to keep your bones as strong as they can be.
Maintain a healthy weight to ease stress and strain on your joints.
Exercise regularly. Exercise keeps your bones strong and helps your joints stay flexible.
Learn more about bone and joint pain and how to manage it.
Eat a healthy diet that includes lots of fresh, unprocessed food, including fruits, vegetables, and lean protein.
Exercise regularly. Exercise helps improve your stamina and has been shown to ease fatigue.
Try a nap in the daytime, but try to keep it short and not sleep past 2 p.m., so you’re able to sleep at night.
Keep to a sleep routine. Go to bed at the same time each night and get up at the same time each morning. Don't stay in bed after you wake up. Make sure you get enough sleep and that you sleep for the same amount of time each night.
Organize each day. Figure out what you have to do and when you need to do it. Pacing yourself helps to conserve your energy. Give yourself more time for activities that take concentration.
Make lists and ask for help. Get help with little things: taking out the trash, folding the laundry, or paying bills. Keep a list of things you need done so when people ask what they can do, you can give them the list.
Learn more about fatigue, including causes and other tips for managing it.
Before you give up on hormonal therapy…
You may get to a point where you feel that the side effects are too much and you want to stop taking hormonal therapy. If you find yourself there, talk to your doctor about your options. You may be able to reduce the dose of the medicine you’re taking or they may have other ideas about ways to reduce troublesome side effects. You may also be able to switch to a different hormonal therapy.
Sharing your feelings with others who are in the same boat can also help. Your nurse or doctor can put you in touch with a support group in your area. There are also online support groups and discussion forums. Discussing your feelings with a therapist can also help you process what you’re going through.
Lastly, please remember to be kind to yourself. Do nice things for yourself and give yourself permission to ask people for help so that you can find moments to rest and recover, for as long as it takes.
This content is made possible, in part, by AstraZeneca, Gilead, Lilly, and Pfizer.
— Last updated on March 1, 2025 at 4:27 PM