Study: New Drug Cuts Breast Cancer Risk in Half

The drug Arimidex reduces the risk of developing breast cancer by more than 50 percent among postmenopausal women at high risk for the disease, according to a new study.

The finding, scheduled for presentation Thursday at the San Antonio Breast Cancer Symposium in Texas, adds hope that Arimidex (anastrozole) might be a valuable new preventive option for some women. The research will also be published in the journal The Lancet.

“Two other antihormone therapies, tamoxifen and raloxifene, are used by some women to prevent breast cancer, but these drugs are not as effective and can have adverse side effects, which limit their use,” study lead author Jack Cuzick said in a new release from the American Association for Cancer Research. 

“Hopefully, our findings will lead to an alternative prevention therapy with fewer side effects for postmenopausal women at high risk for developing breast cancer,” said Cuzick, head of the Cancer Research U.K. Centre for Cancer Prevention and director of the Wolfson Institute of Preventive Medicine at Queen Mary University of London.

About 80 percent of U.S. breast cancer patients have tumors with high levels of hormone receptors, and these tumors are fueled by the hormone estrogen. Arimidex prevents the body from making estrogen and is therefore used to treat postmenopausal women with hormone receptor-positive breast cancer.

The study included more than 3,800 postmenopausal women at increased risk for breast cancer due to having two or more blood relatives with breast cancer, having a mother or sister who developed breast cancer before age 50, or having a mother or sister who had breast cancer in both breasts.

About half the women took Arimidex for five years while the others took a placebo, or dummy drug. Those who took the drug were 53 percent less likely to develop breast cancer than those who took the placebo. Side effects among the women taking the drug included hot flashes and small increases in muscle aches and pains.

The study received funding from the drug companies AstraZeneca and Sanofi-Aventis, and Cuzick is on the speaker’s bureau for AstraZeneca.

Two breast cancer experts in the United States expressed optimism about the new findings.

“This is very exciting information,” said Dr. Amy Tiersten, associate professor of medicine at the Icahn School of Medicine at Mount Sinai, in New York City. She said that although tamoxifen and raloxifene can also cut a woman’s odds for breast cancer, “these medications can slightly increase the risk of blood clots and uterine cancer.”

“It is great to have a less toxic option to offer patients in the preventative arena,” she said of Arimidex.

Dr. Stephanie Bernik, chief of surgical oncology at Lenox Hill Hospital in New York City, agreed. “It is with open arms that we can add [Arimidex] to the medications that can be offered to postmenopausal women that are at high risk of developing breast cancer,” she said.

“Because [Arimidex] has less side effects, more women are likely to undergo preventive treatment,” Bernik said. “This will eventually help decrease the incidence of breast cancer in women in this category.”

“We are planning to continue following the study participants for at least 10 years, and hopefully much longer,” study author Cuzick said. “We want to determine if [Arimidex] has a continued impact on cancer incidence even after stopping treatment, if it reduces deaths from breast cancer, and to ensure that there are no long-term adverse side effects.”