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New Breast Cancer Drug Has Fewer Side Effects

Olga Wexler, left, and Judy Cahill, center, both took raloxifene as part of the STAR Trial. After four years, they, along with participant Joanne Stein, are breast cancer free.
Joe Palca, NPR
Olga Wexler, left, and Judy Cahill, center, both took raloxifene as part of the STAR Trial. After four years, they, along with participant Joanne Stein, are breast cancer free.

Scientists today announced the winner in a head-to-head competition of two drugs to prevent breast cancer. After following nearly 20,000 women for an average of four years, researchers at the cancer consortium known as the National Surgical Adjuvant Breast and Bowel Project (NSABP) declared the drug raloxifene the winner over tamoxifen.

The decision to compare raloxifene with tamoxifen came after a 1998 study, which showed tamoxifen could reduce breast cancer risk by half in women at high-risk for the disease.

But tamoxifen had well-known and dangerous side effects. It increases a woman's risk of uterine cancer, for example. So scientists wanted to find something that works at least as well, but would be safer to take.

The best candidate was raloxifene, also known by the trade name Evista. Preliminary studies showed it had a protective effect against breast cancer, and it was already approved by the Food and Drug Administration for osteoporosis.

But such a study would require thousands of healthy women without breast cancer, but at increased-risk for the disease. And they'd have to be willing to take a drug that might help them, but might also make them sick.

Judy Cahill, a beautician who lives in Huntington Valley, Pa., is one of the study participants at the Fox Chase Cancer Center in Philadelphia. "Somebody has to do it," she said. "Somebody has to be the guinea pig. And I don't mind that because I'm doing this for my daughter, my daughter-in-law... Breast cancer is such a pervasive, invasive, ugly disease."

Olga Wexler signed on for similar reasons: "I have the misfortune of coming from a very long line of breast cancer victims," she says. And when she saw the opportunity to fight back, Wexler said "count me in."

The NSABP study these women participated in found that raloxifene was equally effective in reducing the incidence in invasive breast cancer, the same as tamoxifen.

Not only was raloxifene as good as tamoxifen in preventing breast cancer, but it also appeared to cause fewer dangerous side effects, said Norman Wolmark, NSABP chairman.

"The incidence of uterine cancer was reduced by 36 percent, deep vein thrombosis was reduced by 29 percent, and pulmonary emboli by 36 percent," Wolmark said.

Although the risks of these life-threatening side effects went down, they were still there. And that poses a problem.

"When we ask women to consider taking a drug to prevent something, we're asking them to take a medicine every day for something that may or may not happen to them in the future," says Joy Melnikow, a professor of family and community medicine at the University of California, Davis.

Apart from the fact that the drugs may cause serious side effects, even the relatively minor ones like hot flashes can make the drugs hard to tolerate, says Melnikow.

And while Garnet Anderson of the Fred Hutchinson Cancer Center in Seattle agrees that raloxifene is the winner in the latest study, she is not bowled over by the result.

"Whether raloxifene is truly a home run, I don't see it quite that strongly," says Anderson. "I see they have established a somewhat better risk-benefit profile, but it's not an earth-shattering, major leap in breast-cancer prevention."

Cahill, Wexler and Joanne Stein say they have no regrets about their decision to participate.

"I haven't had to have any biopsies, I haven't had any new lumps or bumps or anything, and I've had normal mammograms and I'm extremely happy," says Stein.

"How often does just your average person get to do something that truly matters?" adds Wexler. "No one may remember that I did this. But I'll remember."

All three women say they are well and breast-cancer free. But for other women at risk of getting breast cancer, it's still a difficult decision whether the possible benefits are worth the possible risks.

Copyright 2022 NPR. To see more, visit https://www.npr.org.

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Joe Palca is a science correspondent for NPR. Since joining NPR in 1992, Palca has covered a range of science topics — everything from biomedical research to astronomy. He is currently focused on the eponymous series, "Joe's Big Idea." Stories in the series explore the minds and motivations of scientists and inventors. Palca is also the founder of NPR Scicommers – A science communication collective.