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Hormone Treatment for Breast Cancer

British Columbia Specific Information

Breast cancer is the most common type of cancer in women in British Columbia. Breast cancer can occur in men as well, but it is not as common. Tests and treatments for breast cancer vary from person to person, and are based on individual circumstances. Certain factors such as your age, family history, or a previous breast cancer diagnosis may increase your risk of developing breast cancer. For information about your specific risk factors, speak with your health care provider.

A number of screening methods, including mammograms in women, can help find and diagnose breast cancer. The decision to have a mammogram or use any other screening method may be a difficult decision for some women. While screening for breast cancer is often recommended, it is not mandatory. Speak with your health care provider for information regarding how to get screened, the facts and myths about screening tests, how to maintain your breast health, and to get help making an informed decision.

For more information about breast cancer and breast cancer screening, visit:

If you have questions about breast cancer or medications, speak with your health care provider or call 8-1-1 to speak with a registered nurse or pharmacist. Our nurses are available anytime, every day of the year, and our pharmacists are available every night from 5:00 p.m. to 9:00 a.m.

Topic Overview

Some breast cancers need the hormones estrogen or progesterone to grow. These cancer cells have "receptors" on their surfaces. Receptors are like doorways to let hormones in.

These types of breast cancer are called estrogen-receptor-positive (ER+) or progesterone-receptor-positive (PR+) breast cancer.

Hormone treatment keeps these cancers from getting the hormones they need. It's like starving the cells so that they stop growing. Sometimes they even shrink.

Treatment works in one of two ways:

  • It lowers the amount of hormones your body makes.
  • It blocks the receptors so that the hormones can't get inside to feed the cancer cells.

Hormone treatment may be used:

  • After treatment for early-stage breast cancer, to reduce the chances that the breast cancer will come back.
  • To prevent breast cancer in women who have a higher risk for breast cancer and who want a way to lower their risk.
  • To treat advanced breast cancer or breast cancer that has spread beyond the breast.

Types of hormone treatment

Medicines include:

  • Selective estrogen receptor modulators (SERMs). Examples are raloxifene (Evista) and tamoxifen (Nolvadex). These drugs block the receptors on the surface of cancer cells.
  • Aromatase inhibitors. These drugs include anastrozole (Arimidex), exemestane (Aromasin), and letrozole (Femara). These block the enzyme aromatase, which converts other hormones to estrogen. They are used mostly in women who are past menopause.
  • GnRH agonists or LH-RH agonists. These drugs include goserelin (Zoladex) and leuprolide (Lupron). They stop your ovaries from making estrogen.
  • Fulvestrant (Faslodex). This drug changes the receptors so that they can't take in estrogen.

Hormone treatment sometimes involves surgery to remove the ovaries or radiation treatments to the ovaries. The goal is to stop the ovaries from making estrogen.

Side effects of hormone medicines

Side effects depend on the drug that is used.

  • SERMS: The most common side effects are hot flashes, mood swings, and feeling very tired. These drugs may also cause blood clots, stroke, and endometrial cancer.
  • Aromatase inhibitors: They can cause headaches, nausea, diarrhea, aching joints, and hot flashes. You also have a risk of bone thinning if you use these medicines for a long time.
  • GnRH agonists and LH-RH agonists: They can cause hot flashes, mood swings, vaginal dryness, less interest in sex, trouble sleeping, and headaches. Risks also include bone thinning.
  • Fulvestrant: Common side effects include nausea, lack of energy, and weight gain. It may also cause vomiting, diarrhea, headache, back pain, and hot flashes.

Side effects of surgery

  • Removing your ovaries makes you start menopause, if you haven't started it already. Menopause often has symptoms like hot flashes, vaginal dryness, urinating often, and having less interest in sex. And it raises your risk for other diseases, like heart disease and osteoporosis.
  • When your ovaries are removed, you can no longer get pregnant.

Managing side effects

Some hormone treatments cause menopause symptoms like vaginal dryness, mood swings, and hot flashes. If you have mild symptoms, you may get some relief if you eat healthy foods, exercise, and lower your stress.

Talk to your doctor if you have severe symptoms that aren't helped by making changes to your lifestyle. You may be able to take medicine to help your symptoms.

Some hormone treatments cause thinning bones. Talk to your doctor to make sure you are doing all you can to protect your bones.


Current as of:
September 8, 2021

Author: Healthwise Staff
Medical Review:
E. Gregory Thompson MD - Internal Medicine
Kathleen Romito MD - Family Medicine
Jimmy Ruiz MD - Hematology, Oncology
Wendy Y. Chen MD, MPH MD, MPH - Medical Oncology, Hematology
Adam Husney MD - Family Medicine