Few women taking breast cancer prevention drugs

Women fear breast cancer more than almost any other illness. Wouldn't it be wonderful, many have wondered, if there were a drug that could prevent the disease? As it happens, there is. In fact, there are several. But just about no one takes them, says Rowan Chlebowski, professor of medicine at the University of California-Los Angeles' David Geffen School of Medicine. The Food and Drug Administration has approved two pills to prevent breast cancer in older women or those at high risk: tamoxifen, a standard of breast cancer therapy, and raloxifene, also known as Evista, commonly used to treat osteoporosis. Both cut the risk of breast tumors by about half. But both can cause significant side effects. Tamoxifen and raloxifene both increase the risk of life-threatening complications such as blood clots, according to the National Cancer Institute. The drugs are used by only 1% to 4% of eligible women — those who are at least 60 years old, or younger women with other risk factors, such as a close relative with breast cancer, Chlebowski says. But Chlebowksi says new research may persuade more women to try a cancer prevention drug. In a study of 4,520 post-menopausal women at high risk for breast cancers, Chlebowski and colleagues found that a drug called exemestane reduced the risk of breast cancer by 65%, without causing as many serious side effects as other pills. Doctors have not studied the drug in younger women without additional risk factors. Exemestane is already on the market and commonly prescribed to breast cancer patients to keep their tumors from coming back. The drug, sold under the brand name Aromasin, belongs to a class of medications called aromatase inhibitors, which deprive breast cancers of estrogen, a hormone that fuels the majority of breast tumors. Researchers followed women in the study closely because aromatase inhibitors can cause side effects, such as bone loss. Yet doctors found no increase in osteoporosis, bone fractures, high cholesterol or heart attacks, according to the study, being presented Saturday at the American Society of Clinical Oncology's annual meeting in Chicago. Pfizer, which makes exemestane, helped fund the study. The biggest problem for women taking exemestane was joint pain, with 3.5% reporting severe joint pain, compared with 1.5% of women taking a placebo, Chlebowski says. "This is very exciting news," says Terese Bevers, a breast cancer specialist at Houston's M.D. Anderson Cancer Center, who wasn't involved in the new research. "It's the opportunity to never have to tell a woman, 'You have breast cancer.'" Bevers says high-risk women now have a menu of options to prevent breast cancers. If they develop side effects on one of the three drugs, they can try another, she says. Chlebowski notes that cost could keep women from trying exemestane. The brand drug costs $300 to $400 a month, he says. That price could drop in coming months, however, when exemestane's patent expires. Yet, some experts say women should still be cautious. There's no evidence any of these actually save lives, says Vered Stearns of the Johns Hopkins University School of Medicine. That may be because the drugs only prevent slow-growing or less aggressive tumors, which can be cured through standard treatment, Stearns says. Patricia Ganz, who treats high-risk women at the UCLA School of Medicine, notes that the study only tracked women for three years. So it's possible that more will develop side effects over time, says "One study does not change therapy," says Ganz, who wasn't involved in the new research. Researchers could resolve many questions about exemestane through a study that directly compares it with tamoxifen or raloxifene, Ganz says. And in spite of exemestane's success, many doctors may not be comfortable prescribing it, says Claudine Isaacs of Georgetown's Lombardi Comprehensive Cancer Center. Although cancer specialists have used exemestane for years, few primary care doctors are familiar with it. Gynecologists and other doctors whom women consult about breast cancer prevention may remain reluctant to suggest it, Isaacs says.