Study: Femara and Arimidex Useful in Advanced Breast Cancer (dateline March 3, 2004) | Breast Health News | Imaginis - The Women's Health & Wellness Resource Network

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Study: Femara and Arimidex Useful in Advanced Breast Cancer (dateline March 3, 2004)

Tamoxifen is the most common drug treatment for advanced breast cancer. However, at some point, patients may become resistant to tamoxifen and require additional drug options. A new study finds that the drugs Femara (generic name, letozole) and Arimidex (generic name, anastrozole) both slow the progression of advanced breast cancer that has been previously treated with tamoxifen. The research shows confirms that Femara is more powerful than Arimidex in shrinking and eliminating breast cancer tumors.

Femara was approved by the U.S. Food and Drug Administration (FDA) in 1997 to help treat advanced breast cancer in women whose breast cancer tumors have not responded well to tamoxifen. Femara works by reducing the total amount of estrogen in the body (circulating estrogen levels), thereby limiting the amount of estrogen that can affect breast cancer cells. In post-menopausal women, the body produces estrogen from other hormones known as androgens by the action of an enzyme called aromatase. Femara is an aromatase inhibitor and blocks aromatase from converting androgen into estrogen, thus lowering the amount of estrogen in the body. Arimidex was also approved by the FDA to treat advanced breast cancer after a first-line treatment with tamoxifen. Like Femara, Arimidex is also an aromatase inhibitor and decreases the production of estrogen.

Researchers have known that Femara is a more powerful drug than Arimidex in terms of shrinking breast cancer tumors. However, Dr. C. Rose, from the Lund University Hospital in Sweden and colleagues wanted to determine whether both drugs could effectively slow the progression of breast cancer in patients with advanced stages of the disease.

To conduct their study, Dr. Rose and colleagues studied 713 advanced breast cancer patients who had been treated with tamoxifen as a first-line therapy. Then, the women were treated with either Femara or Arimidex. Approximately 19% of the women who were treated with Femara experienced a shrinkage or disappearance of their tumors while 12% of the women treated with Arimidex experienced similar results. Cancer treated with either drug took about six months to progress.

Thus, the researchers conclude that advanced breast cancer responds more effectively to Femara than Arimidex as a second-line treatment, after using tamoxifen. Both drugs were well-tolerated in the study and did not differ in terms of safety. In addition, the rate of cancer progression was equal with both drugs.

Possible side effects of Femara may include:

  • Musculoskeletal pain (pain in the skeleton or legs, arms or back)
  • Nausea
  • Headache
  • Joint pain
  • Fatigue
  • Difficulty breathing

Possible side effects of Arimidex may include:

  • General feeling of weakness
  • Decreased energy level
  • Headache
  • Nausea
  • Mild diarrhea
  • Increased or decreased appetite
  • Sweating
  • Hot flashes
  • Vaginal dryness
  • Temporary hair thinning

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