Postmenopausal (search) women with early breast cancer have fewer recurrences after surgery when they take Femara (search) instead of tamoxifen (search), new research shows.

The results were announced at the Primary Therapy of Early Breast Cancer 9th International Conference in Switzerland. Femara's maker, Novartis, funded the study. Novartis is a WebMD sponsor.

The study posed a key question: Which drug is better at reducing the risk of breast cancer's return in postmenopausal women who have had breast cancer (search) surgery?

Survival More Common

The issue affects thousands of women. It’s becoming more common to survive breast cancer.

There are more than 2 million U.S. women who are breast cancer survivors, says the American Cancer Society (ACS).

This year, more than 211,000 U.S. women will be diagnosed with breast cancer, the ACS estimates. About 40,000 will die of the disease. For survivors, keeping cancer at bay is a top priority.

Drugmaker’s Study

More than 8,000 women in 27 countries participated in the study. All had undergone breast cancer surgery and were postmenopausal. Their breast cancer was treated early; it hadn’t spread beyond the breast and lymph nodes (search).

The women’s tumors were dependent on the hormone estrogen to grow. About two-thirds of breast cancers are fueled by estrogen (search), says the ACS.

Typically, women take tamoxifen for about five years. About 500,000 U.S. women take tamoxifen and 80,000 join their ranks each year.

How the Drugs Work

Femara and tamoxifen both lower the amount of estrogen in the body, slowing the growth of estrogen-dependent tumors. But they work differently.

Tamoxifen blocks estrogen receptors. It’s the standard treatment for postmenopausal women with estrogen-dependent tumors. Tamoxifen was a major breakthrough when it debuted more than 25 years ago. It’s also used to prevent breast cancer in women at high risk for the disease.

Femara takes a different approach. It’s the second in a newer class of breast cancer drugs called aromatase inhibitors.

Aromatase inhibitors target aromatase, which is needed to turn male-type hormones called androgens into estrogen. Thwarting aromatase prevents androgens (search) from morphing into estrogen. As a result, estrogen levels are lower.

Surviving Cancer-Free

The women were studied for 26 months, on average. They were assigned to different treatment plans to see which treatment plan worked best to reduce the risk of the recurrence of breast cancer.

One group took tamoxifen or Femara for five years. Another group of women took tamoxifen for two years, followed by three years on Femara. A third group of women got the opposite approach – two years of Femara followed by three of tamoxifen.

The results showed that compared with tamoxifen, Femara cut the risk of recurrence of breast cancer by 19 percent.

Femara significantly increased survival free of breast cancer, especially reducing the risk of the spread of breast cancer to distant parts of the body.

Side Effects

Women taking Femara were more likely to have bone fractures. Higher cholesterol was also more common with Femara, though the effect was “usually mild,” says Novartis. Heart attack and stroke were rare with both drugs but occurred slightly more often with Femara, says Novartis. Femara should not be taken during pregnancy.

Tamoxifen also had side effects including clotting, vaginal bleeding, and changes in the womb’s lining (the endometrium).

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Primary Therapy of Early Breast Cancer 9th International Conference, St. Gallen, Switzerland, Jan. 26-29, 2005. News release, Novartis. American Cancer Society. WebMD Medical News: “Breast Cancer Drug Takes Big Step Toward First Place.” WebMD University: “Alive & Well: Taking Charge of Your Breast Cancer Treatments -- Tamoxifen, What It Is, Why You May Need It.” Reuters. Associated Press.