Science, medicine: Restrained New world

Breast cancer drugs hold out hope -- but not certainty

By Steven Milloy
Copyright 1998 Philadelphia Inquirer
May 23, 1998

The news on women's health seems promising. Tamoxifen reduced the risk of breast cancer by 50 percent in a recent clinical trial. News reports say the new osteoporosis drug, raloxifene, reduces the risk of breast cancer and heart disease. Good news, right? Let's hope. In the meantime, don't bet your life on it.

Even if tamoxifen really can prevent breast cancer as touted, this news has little value to the average woman.

Let's say out of every 1,000 women, about 30 get breast cancer. Which 30 will get breast cancer? No one knows. Breast cancer can't be predicted with anything close to certainty, even in women with well-established risk factors. Assuming tamoxifen reduces breast cancer incidence by 50 percent, only about 15 women will develop breast cancer. Which 15? Once again, no one knows. So all 1,000 women must remain vigilant. Tamoxifen is not a vaccine.

In mid-April came raloxifene. The Food and Drug Administration approved it last December as a drug to prevent osteoporosis in women. But it has also been marketed as a safer'' alternative to estrogen-based hormone replacement therapy (HRT) in menopausal women.

HRT indeed has been used successfully for 55 years to ease menopausal symptoms such as hot flashes and to prevent and treat bone loss. And it may possibly also have beneficial side effects, including reducing the risk of heart disease and aiding in the prevention of Alzheimer's disease.

But there is much controversy with regard to HRT and breast-cancer risk. In some studies, risk increased; others show no increase or even a decrease in breast cancer. Yet raloxifene has been marketed as an anti-estrogen'' - implying that it provides the benefits with none of the risks. This pitch got a lift in mid-April when news reports claimed that, in a clinical trial, raloxifene was even more effective in reducing breast-cancer risk than tamoxifen, cutting breast-cancer incidence in the trial by 70 percent.

But as with tamoxifen, a woman taking raloxifene can have no peace of mind concerning breast-cancer risk. Contrary to the hype, raloxifene is not a vaccine either.

Recently, on NBC Nightly News, senior science correspondent Robert Bazell reported a study showing that raloxifene lowered LDL, the bad cholesterol, by 12 percent and thus reduce(d) a woman's chances of heart disease.'' Only partly correct. The study did report that raloxifene favorably alters markers of cardiovascular risk'' by decreasing LDL. But the authors also concluded that further clinical trials are necessary to determine whether these favorable biochemical effects are associated with protection against cardiovascular disease.''

This sentiment was echoed in an accompanying Journal of the American Medical Association editorial, in which Basil M. Rifkind and Jacques E. Roussow wrote that the uncertainties about the cardioprotective effect of estrogens apply doubly to raloxifene.''

Heart disease and breast cancer are responsible for about 30 percent and 4 percent, respectively, of women's deaths annually. Though breast cancer is not preventable, more than 90 percent of breast cancers can be treated successfully if detected early. So it makes sense for women to have regular checkups for breast cancer.

But relying now on the as-yet-unfulfilled hope of breast cancer vaccines'' is risky. The best way to reduce the risk of heart disease currently is to eat right, exercise and avoid smoking. Don't be misled by the good'' news of miracle drugs that aren't.

Steven Milloy is executive director of The Advancement of Sound Science Coalition.

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