In a letter to the FDA, Cindy Pearson, executive director of the National Women's Health Network (NWHN), elegantly laid out the truth about an ad for tamoxifen that appeared in Newsweek... The ad is an excellent example of how statistics are deceptively used both in advertising and in writing abstracts of published studies:
"The ad is misleading because of the shifting use of absolute and relative risk numbers. By juxtaposing test reading "women who took Nolvadex (tamoxifen) had 44% fewer breast cancers than women taking sugar pills," with text asserting that health threatening side effects "occurred in less than 1% of women," Zeneca (the drug maker) is deliberately creating an inaccurate impression of the risk/benefit of this drug. The average consumer reading this text would understand that she has a 44% chance of benefiting from taking tamoxifen and less than a 1% chance of experiencing the associated risks.
If the ad used relative risk consistently, it would say that women who took tamoxifen had 44% fewer breast cancers and 253% more endometrial (uterine) cancers. Or alternatively, if Zeneca wants to use the absolute numbers to assert that women have a less than 1% chance of being harmed by tamoxifen, the ad should also explain that in absolute terms the women have only a 1-2% chance of benefiting from the drug depending on their underlying risk of getting breast cancer in the first place.
We hope the FDA will act quickly and strongly... This is not the first misleading advertisement of this promotional campaign... Tamoxifen is not a risk-free drug. Healthy women have already died as a result of taking tamoxifen..."
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Many doctors prescribe tamoxifen as a matter of course to virtually all women with breast cancer, regarless of age or whether they have a uterus and apparently without regard to the National Cancer Institute study warning against such indiscriminate use. (p. 229-232) For the most part, it's only in the United States that doctors still believe tamoxifen significantly prevents or reverses breast cancer. In fact, now even the National Cancer Institute has come out with a statement that in all but a very narrow group of women under the age of 60, tamoxifen may do more harm than good in terms of preventing cancer. Despite this, the Food and Drug Administration just approved the use of tamoxifen to treat a form of breast cancer known as ductal carcinoma in situ or DCIS. (These are not breast cancers at all - but benign tumors.) (p.10)
If the side effects of tamoxifen are this bad, why is it being used at all, and why is it being trumpeted so loudly as the great cure-all, to the extent that the FDA approved its use as a preventive? ... It's the lesser of many evils; it's better than nothing. Theoretically - on paper, in test tubes and in laboratory animals - tamoxifen looks promising and the rationale for using it is based on solid scientific foundations. (p.9)
Just in case you're wondering about the profitability of a drug like tamoxifen, it's estimated that at least 60% of women with breast cancer are taking tamoxifen and at a cost of about $1,000 per year each, that's one billion dollars a year going into the pockets of the drug companies. (p. 232)
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Update – July, 2006 in the magazine, Cancer
Tamoxifen Fails to Reduce Breast Cancer Risk in Most Women
by Allison Gandey
A new study suggests that current recommendations for tamoxifen use should be amended to promote the drug for only the highest-risk women.
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