Ask first before taking breast cancer drug
August 26, 2002

By Rita Rubin
USA TODAY

Women who are considering taking medication to reduce their high risk of breast cancer need to talk with their doctor about whether such a move is likely to cause more harm than good, according to recommendations out today from an independent, government-sponsored panel.

Tamoxifen, sold as Nolvadex, is the only drug approved to reduce breast cancer risk in healthy women. Many doctors prescribe raloxifene, sold as Evista, for that same purpose although it’s only approved for osteoporosis. (Doctors can legally prescribe drugs for uses other than approved.)

Long used to prevent new tumors in women already diagnosed with breast cancer, tamoxifen was approved in 1998 to reduce the chance of the disease in high-risk healthy women.

A U.S. study of more than 13,000 high-risk women had found that those randomly assigned to receive tamoxifen were about half as likely to develop breast cancer as those assigned to get a placebo. Women were considered to be high risk if their chance of developing breast cancer in the next five years -based on such factors as family history of the disease and personal history of breast biopsies - was higher than 1.7 percent.

But the study also found that tamoxifen carries its own risks, such as an increased chance of uterine cancers and blood clots in the legs and lungs.

After reviewing the U.S. study and two European randomized trials of tamoxifen, the U.S. Preventive Services Task Force concurred that only high-risk women should take the drug. In general, though, the task force says that the benefit outweighs the harm only in certain groups of high-risk women:

— Women in their 40s who aren’t predisposed to blood clots. That would exclude those who smoke or have high blood pressure.

— Women in their 50s who are not predisposed to blood clots and do not have a uterus. The chance of developing a blood clot or uterine cancer as a result of tamoxifen increases with age, as does breast cancer risk.

The recommendations appear in the “Annals of Internal Medicine”.

“The recommendations are pretty narrow and pretty cautious,” says task force chair Janet Allan, a nurse practitioner and dean of the School of Nursing at the University of Texas Health Science Center at San Antonio.

Allan’s task force found more evidence for the benefits of tamoxifen than for the benefits of raloxifene. The only recent randomized trial found that women given raloxifene were less likely to develop breast cancer than those given a placebo. But that study included women who weren’t at high risk to begin with, and it was designed to test the drug’s effect against osteoporosis.

Nearly 14,000 women have enrolled in a nationwide study comparing tamoxifen’s and raloxifene’s effect on women at high risk for breast cancer.

Few of the millions of U.S. women at high risk for breast cancer take tamoxifen, says Leslie Ford of the National Cancer Institute’s prevention division. One reason, she says: Women tend to over-estimate their risk, so when they learn it’s “only,” say, 5 percent over the next five years, they’re actually relieved.

“Ten years ago we didn’t think it was possible to reduce your risk of breast cancer with a drug,” Ford says. “Now we know it is, so we debate about whether women should take it or not.”