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Breast Cancer Health Center

Tamoxifen for Breast Cancer Treatment and Prevention

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Is tamoxifen prescribed for breast cancer prevention?

Tamoxifen is used in "primary prevention" of breast cancer in women who have no history of breast cancer. This drug reduces the risk of developing breast cancer in two ways:

1. Tamoxifen blocks the action of estrogen on estrogen-sensitive cancer cells.

2. It blocks estrogen from acting on cells that are not cancerous.

Tamoxifen inhibits the increase and division of healthy breast cells. That way, it also reduces the number of cells that might have cancer-causing DNA damage.

Findings from a study of more than 13,000 women at high risk for developing breast cancer revealed that women who received tamoxifen for five years developed fewer breast cancers than women who received a placebo for five years. Newer research suggests that taking tamoxifen for 10 years lowers the risk even further.

Another study sponsored by the National Cancer Institute revealed about a 50% reduction in breast cancer occurrence among high-risk women who took tamoxifen. The study also showed that tamoxifen reduced the chance of osteoporosis bone fractures of the hip, wrist, and spine by about 32% among study participants.

Is tamoxifen a safe breast cancer treatment?

The overall consensus is the benefits of tamoxifen as a treatment for breast cancer far outweigh the potential risks associated with this medication.

Along with preventing breast cancer, tamoxifen is often used as a successful breast cancer treatment for both advanced and early-stage breast cancers. It's prescribed for women who have had cancer in one breast in order to reduce the risk of cancer in the second breast. In addition, scientific studies support the use of tamoxifen in treating women with ductal carcinoma in situ (DCIS), a type of breast cancer that may lead to invasive breast cancer.

What are the side effects of tamoxifen?

Some experts believe that the prevention benefits of tamoxifen should be cautiously weighed considering its cost, and its side effects, which are potentially serious.

Side effects of tamoxifen can be dangerous, even deadly, and include:

  • Blood clots
  • Strokes
  • Heart disease 
  • Uterine cancer
  • Cataracts

Milder side effects of tamoxifen may include menopause-like symptoms such as:

  • Vaginal dryness
  • Hot flushes
  • Leg cramps
  • Joint pain

In addition, tamoxifen may cause menstrual irregularities and sexual dysfunction.

If you have been diagnosed with breast cancer or are at high risk for breast cancer, talk with your doctor to see if tamoxifen is right for you. Together, you can weigh the benefits and risks of this drug to make sure you get the healthiest outcome.

WebMD Medical Reference

Reviewed by Melinda Ratini, DO, MS on September 02, 2014
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