ROBERT SIEGEL, host:
From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel.
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And I'm Michele Norris.
Scientists are reporting what they say is the best evidence yet that there's a drug that can prevent breast cancer. The drug is tamoxifen. It's primarily used for women who've already had breast cancer. And as NPR's Joe Palca reports, some scientists doubt how useful it will be for women who haven't had breast cancer.
JOE PALCA reporting:
During the 1990s slightly more than 13,000 women took part in the breast cancer prevention trial. Half took the drug tamoxifen and half an inert placebo. All women were supposed to participate for five years. In 1998 scientists stopped the study after only three and a half years because tamoxifen appeared to be preventing a significant number of breast cancers. But scientists kept track of the participants, and now they've completed a study of what's happened since then.
Mr. BERNARD FISHER (NSABP): It clearly shows that the results initially presented hold up.
PALCA: Bernard Fisher of the cancer study consortium called NSABP headed the prevention trial. He's now 87 years old. He's helped revolutionize breast cancer treatment in this country by proving that mastectomies were frequently unnecessary. Now he hopes to revolutionize breast cancer prevention. He says the breast cancer prevention trial showed that tamoxifen benefitted women at high risk of breast cancer.
Mr. FISHER: There was approximately about a 50 percent reduction of invasive breast cancers in women who received the drug compared to those who did not.
PALCA: That's a big improvement. But the news is not all good. Women taking tamoxifen were more likely to get uterine cancer and more likely to suffer blood clots. Still, Fisher says for women at the highest risk of breast cancer, there was a net benefit from taking the drug.
The new study appears in the Journal of the National Cancer Institute. Health psychologist Sharon Bober agrees that tamoxifen is probably right for some women. She studied more than a hundred women who are eligible for the drug.
Ms. SHARON BOBER (Psychologist): What we were struck by was that all of these women were at high risk. You know, an oncologist would tell you that it was a no-brainer. All of these women would benefit from taking tamoxifen. And what we found was that probably about half opted to take tamoxifen and about half did not.
PALCA: Bober believes part of the reason for that is that it's hard to convey information about medical risk. She says many women in her study were worried that taking tamoxifen simply meant trading one health risk for another. But Bober says in many cases a woman's risk of breast cancer is far greater than any health risk caused by tamoxifen.
Ms. BOBER: I'm not, in any way, trying to sort of disrespect the individual decision, but my concern is that often those decisions aren't really grounded in kind of a really strong realistic understanding of what people are dealing with.
PALCA: But some experts say there are other studies of tamoxifen that show a different picture of the drug's risks and benefits. Jack Cuzick of Cancer Research UK is running another large study comparing tamoxifen with placebo for cancer prevention. His study has shown a smaller benefit from tamoxifen. He says healthy women are right to hesitate before taking the drug.
Mr. JACK CUZICK (Cancer Research UK): And the fact that tamoxifen has not been accepted in the United States in very many places for prevention is, I think, a strong indication that the trial has not convinced people that this is an adequate approach for prevention at this stage.
PALCA: Cuzick says there are some new drugs being tested that may be better than tamoxifen. Bernard Fisher agrees that safer drugs may be coming along. He says there's a study of more than 19,000 women that's comparing tamoxifen and the osteoporosis drug raloxifene, also called Evista, to see which is better at preventing breast cancer and, equally important, which has fewer side effects. But the results of those studies are months, if not years, off.
Mr. FISHER: Until one of the trials that's now going on demonstrates a greater net benefit from some alternative therapy, tamoxifen remains the only proven chemopreventive treatment for breast cancer risk reduction. I think we can safely say that.
PALCA: In the meantime, women and their doctors still face difficult decisions about whether or how to try to prevent breast cancer. Joe Palca, NPR News, Washington.
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