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Breast Cancer and Endocrine Therapy

Breast Cancer and Tamoxifen continued...

People who should not use tamoxifen include:

  • Pregnant women
  • Women planning to become pregnant
  • Men or women with a history of blood clots or stroke, or those who are taking blood thinners, also called anticoagulants

Talk to your doctor to see if tamoxifen is right for you.

For women, the side effects of tamoxifen are similar to some of the symptoms of menopause. Two of the most common side effects are hot flashes and vaginal discharge. Other tamoxifen side effects in women may include:

  • Vaginal dryness and/or itching
  • Irregular menstrual periods
  • Headache
  • Nausea and/or vomiting
  • Skin rash
  • Fatigue
  • Fluid retention and/or weight gain

While some of its side effects are similar to menopausal symptoms, tamoxifen does not cause a woman to begin menopause.

Tamoxifen's side effects in men may include:

  • Headache
  • Nausea and/or vomiting
  • Skin rash
  • Sexual side effects including impotence or decrease in sexual interest

Are There Risks to Taking Tamoxifen?

Yes. The risks of taking tamoxifen include:

  • Fertility. Tamoxifen may affect fertility, so it is important to use some form of barrier birth control while you are taking it. However, do not use oral contraceptives (the "pill") since they may change the effects of tamoxifen and effect the breast cancer. Tell your doctor right away if you think you may have become pregnant while taking this medication.
  • Increased blood clots. Women taking tamoxifen may have a slightly increased risk of developing blood clots in the lungs or large veins. This risk is increased in smokers.
  • Increased risk of stroke.
  • Uterine cancer/sarcoma. Tamoxifen may increase a woman's risk of developing uterine cancer (cancer of the lining of the uterus) or uterine sarcoma. However, this risk is very small and needs to be balanced against the significant benefits of taking tamoxifen for breast cancer.
  • Cataracts. Taking tamoxifen appears to put some women at increased risk for developing cataracts, a clouding of the lens inside the eye. People have also reported eye problems such as corneal scarring or retinal changes.
  • Medications. Tamoxifen may affect the metabolism of other drugs.


Tamoxifen and Breast Cancer Prevention

In 1998, the National Cancer Institute funded a large study designed to determine whether tamoxifen would reduce the occurrence of breast cancer in healthy women known to be at high risk. The results of the trial showed a 50% reduction in both invasive and non-invasive breast cancer in the treated women.

Tamoxifen has also been shown to substantially reduce the risk of developing invasive breast cancer in women who have had ductal carcinoma in situ (DCIS).

Are There Other Drugs That Can Prevent Breast Cancer?

Another SERM drug, Evista, used to prevent osteoporosis, is similar to tamoxifen and has been shown to prevent breast cancer in high risk women, but with fewer side effects. It has also been approved by the FDA for breast cancer prevention.   

Fareston is another SERM. Like tamoxifen, it blocks certain effects of estrogen and is used as a treatment for advanced breast cancer in postmenopausal women.

WebMD Medical Reference

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