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Hormone Therapy for Breast Cancer

About two-thirds of women with breast cancer have tumors that contain hormone receptors. This means a tumor has receptors for the hormone estrogen (called ER-positive) or the hormone progesterone (PR-positive) or both. Hormone therapy is given to block these hormones and fight the cancer's growth. Women who are ER-positive are more likely to respond to hormone treatment than women who are ER-negative.

Tamoxifen for Breast Cancer

Tamoxifen is a pill taken daily and has been used consistently for decades to treat breast cancer. Tamoxifen can be used in women of any age, regardless of whether they've gone through menopause. Taking tamoxifen for 5 years has been found to reduce the chance of breast cancer recurrence and new breast cancers in women with ER-positive or ER-unknown breast tumors.

Doctors also use tamoxifen to treat breast cancer that has spread to other parts of the body. It's also given to prevent breast cancer in healthy women with a high risk of developing the disease.

Women taking tamoxifen are more likely to develop cancer of the uterus (endometrial cancer) than other women. They should have regular pelvic exams and tell their doctor about any abnormal uterine bleeding. Other risks from tamoxifen include deep vein thrombosis, blood clots in the lungs, stroke, and cataracts. Minor side effects include hot flashes and mood swings.

Tamoxifen also helps prevent osteoporosis, or weak bones.

Aromatase Inhibitors and Breast Cancer

Aromatase inhibitors are medications that treat breast cancer in both early stages and advanced ones. Aromatase inhibitors prevent estrogen from being made. They are effective only in women who are past menopause.

Arimidex (anastrozole), Aromasin (exemestane), and Femara (letrozole) are aromatase inhibitors. They are used to treat ER-positive breast cancer, either following tamoxifen treatment or by themselves. 

Side Effects of Aromatase Inhibitors

One serious side effect of aromatase inhibitors is osteoporosis, which can lead to bone fractures. Bone density tests are used to check for osteoporosis. 

Other side effects include hot flashes, muscle and joint pain, memory problems, and a higher risk of heart disease.

Ovarian Ablation for Breast Cancer

Some women with breast cancer may benefit from ovarian ablation, if they have not yet gone through menopause and their cancer is ER-positive. Ovarian ablation stops the ovaries from making estrogen. This can be done by:

  • Aiming radiation at the ovaries
  • Surgically removing the ovaries
  • Giving the woman a drug called luteinizing hormone-releasing hormone (LHRH) agonist

Ovarian ablation can also be done in combination with tamoxifen. Studies have shown that giving women an LHRH agonist alone or with tamoxifen has been at least as effective as the chemotherapy combination used in hormone-sensitive, early breast cancer and in metastatic breast cancer in premenopausal women.

Before you begin breast cancer treatment, print out Questions to Ask at your first appointment.

Recognizing a Breast Cancer Emergency

Call your doctor if you have:

  • A temperature greater than 100.4 F. If you have a fever and chills, tell your doctor immediately. If you can't reach your regular doctor, go to the emergency room.
  • New sores or patches in your mouth, a swollen tongue, or bleeding gums
  • A dry, burning, scratchy, or "swollen" throat
  • A cough that is new or doesn't go away and has mucus
  • Changes in bladder function, including increased frequency or urgency to go, burning during urination, or blood in your urine
  • Heartburn, nausea, vomiting, constipation, or diarrhea that lasts longer than 2 or 3 days, or blood in your stools

WebMD Medical Reference

Reviewed by Angela Jain on April 15, 2014
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