Hormone Therapy for Breast Cancer


Today, more women survive breast cancer than ever before. Screening exams help us catch breast cancer early. And modern treatments let us remove or kill your cancer before it spreads. It's important to know that hormone therapy is not hormone replacement therapy (HRT). HRT isn't used to treat breast cancer. Rather, it is taken by some women to treat troublesome menopausal side effects such as hot flashes or mood swings. HRT is used to raise estrogen levels that drop after menopause. HRT contains estrogen and can contain progesterone and other hormones. Hormone therapy is exactly the opposite -- it blocks or lowers estrogen levels in the body.

One treatment linked to breast cancer survival is hormone therapy (endocrine therapy). 

Around two-thirds of women with breast cancer may benefit from hormone therapy.

About Breast Cancer & Hormones

Certain types of breast cancer are sensitive to hormones called estrogen and progesterone. Estrogen helps regulate menstruation and promotes breast development. Progesterone also helps control the menstrual cycle, and supports early pregnancy.

These hormones are vital to female development and reproduction, but they can also help breast cancer grow. Certain types of breast cancer have “receptors” that attach to estrogen or progesterone. The cancer feeds off the hormone, then grows and spreads.

These cancers are called hormone receptor-positive breast cancers.

What is Hormone Therapy?

Hormone therapy refers to a group of drugs and other treatments. They include:

  • Drugs that prevent hormones from attaching to cancer cells. These medications include the long-used drug Tamoxifen.
  • Drugs that lower hormone levels, or stop hormone production. These include a class of drugs called aromatase inhibitors (AIs). They’re only used in women who have gone through menopause.
  • Treatments to remove the ovaries or prevent them from working. Before menopause, your ovaries produce most of your estrogen and progesterone. Pre-menopausal women with breast cancer may have their ovaries surgically removed. Or they may take drugs to shut down their ovaries.

The type of hormone therapy you’ll need depends on several factors. These include the kind of breast cancer you have, your age and whether you’ve completed menopause. You may use one drug or a combination of drugs. For example, some women take Tamoxifen for several years then switch to an AI after menopause.

Hormone therapy is usually used with other breast cancer treatments. These include lumpectomy surgery or mastectomy surgery.

Hormone Therapy Benefits

Each type of hormone therapy works differently and offers different benefits. These include:

  • Preventing cancer from coming back.
  • Slowing or stopping the growth of cancer that has spread.
  • Shrinking a tumor before surgery.
  • Lowering the risk of breast cancer in women who are high-risk for developing it.

What to Expect from Hormone Therapy

Your Mercy care team will make sure you understand what to expect before, during and after hormone therapy. For example:

  • You may need to take hormone therapy for 5-10 years.
  • Common side effects include hot flashes, vaginal dryness, mood changes, weight gain and night sweats.
  • Like all medications, hormone therapy drugs have risks. Drugs like Tamoxifen may increase your risk of blood clots or uterine cancer. And AIs may cause joint pain and stiffness, or bone thinning that leads to osteoporosis.

We know breast cancer treatment can feel complicated and overwhelming. We’ll take the time to answer your questions, address your concerns and make sure you feel comfortable and informed before starting any new therapy.

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