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Studies Find Femara More Effective than Tamoxifen for Advanced Breast Cancer (dateline November 14, 2000)

Two new studies show that the drug Femara (generic name, letrozole) may be more effective than tamoxifen for post-menopausal women with advanced (metastatic) breast cancer. Femara is currently approved by the U.S. Food and Drug Administration (FDA) as a second-line treatment for advanced breast cancer, to be used when other therapies do not work. However, researchers believe that based on this research, Femara should be considered as a first option ("first-line therapy") for treating some women with advanced breast cancer.

The two latest studies on Femara were both presented at the Chemotherapy Foundation Symposium XVIII in New York this November. In the first study, which is the largest study on hormonal therapy for advanced breast cancer ever conducted, 900 women with advanced breast cancer received either Femara or tamoxifen (brand name, Nolvadex). After one year of treatment, the number of women whose cancer had not progressed was nearly 50% greater among those who took Femara, compared with the women who took tamoxifen.

According to Matthew Ellis, MD, PhD, Clinical Director of the Breast Cancer Program at Duke University Medical Center, Femara is the first breast cancer treatment that shows consistent superiority over tamoxifen. Dr. Ellis believes that these results could cause physicians to consider a change in practice guidelines for advanced breast cancer, making Femara a first-line therapy for advanced breast cancer.

In the second study presented at the Chemotherapy Foundation Symposium, 324 post-menopausal women with large localized or locally advanced breast cancer tumors were given either Femara or tamoxifen for four months to help reduce the size of their tumor before surgery. Again, the results with Femara were shown to be more effective at shrinking the size of breast cancer tumors: 45% of the women who took Femara could have breast-conserving surgery (lumpectomy) while only 35% of the women who took tamoxifen were candidates for breast-conserving surgery.

The way in which Femara and tamoxifen fight breast cancer is different. To grow and reproduce, breast cancer cells require the female hormone estrogen. Tamoxifen is an "anti-estrogen" and works by blocking estrogen from breast cancer cells, thereby "starving" cancer cells. On the other hand, 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. Other examples of aromatase inhibitors include anastrozole (brand name, Arimidex) and exemestane (brand name, Aromasin). Both of these drugs are also used to help treat advanced breast cancer in women whose breast cancer tumors have not responded well to tamoxifen.

Possible Side Effects of Femara and Tamoxifen



  • Musculoskeletal pain (pain in the skeleton or legs, arms, back)
  • Nausea
  • Headache
  • Joint pain
  • Fatigue
  • Difficulty breathing
  • Hot flashes
  • Vaginal dryness
  • Irregular menstrual cycles
  • Mood changes or depression

The FDA Advisory Committee will meet in December to discuss whether Femara should be recommended for FDA approval as a first-line therapy for advanced breast cancer.

Additional Resources and References