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Breast Cancer and Endocrine Therapy

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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.

Other Hormone Therapies: Arimidex, Femara, and Aromasin

Aromatase inhibitors block the effect of an enzyme that helps the body break down testosterone into estrogen. They include Arimidex and Femara.

Aromatase inhibitors delay the progression of breast cancer longer than tamoxifen in women with advanced breast cancer whose tumors rely on estrogen to grow. Specifically, Femara and Arimidex are used as part of the initial or follow-up treatment of hormone-sensitive breast cancer -- even those that have spread to other parts of the body -- in women who have gone through menopause. They are pills that are taken once a day.

Side effects of aromatase inhibitors include:

  • Nausea, vomiting, diarrhea, and/or constipation
  • Hot flashes
  • Headache
  • Bone pain
  • Severe fatigue
  • Skin rash
  • Swelling and fluid retention
  • Flu-like symptoms
  • Increased bone loss

Another drug, Aromasin, is similar to the aromatase inhibitors but is an aromatase inactivator. Instead of blocking the aromatase enzyme, aromatase inactivators actually destroy it.

Aromasin is currently used to treat postmenopausal women with breast cancer that has spread outside of the breast that was not responsive to tamoxifen. It's a pill taken once a day after meals.

Side effects of Aromasin include:

  • Nausea
  • Fluid retention and/or weight gain
  • Headache
  • Hot flashes

 

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