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Retallying tamoxifen's risks and benefits.

Last year, the National Cancer Institute initiated a disease-prevention trial that will dispense tamoxifen to 8,000 healthy women who are at high risk of development breast cancer (SN: 5/9/92, p.309). Though the treatment poses some risks, expected benefits of the drug far outweigh them, the trial's designers have said. But that weighing of the pros and cons underestimated the frequency of some reported complications and failed to account for several others altogether, according to two epidemiologists at Johns Hopkins University in Baltimore.

In the just-released EPIDEMIOLOGIC REVIEWS (Vol.15, No. 1), Trudy L. Bush and Kathy J. Helzlsouer reevaluate the drug's trade-offs. Their conclusion: For this population, the trial is a likely to prove tamoxifen a net detriment as a benefit.

Planners of the tamoxifen trial have estimated that their five-year program will prevent 62 breast cancers and 52 heart attacks, Bush and Helzlsouer note. However, on the basis of the age of the study recruits and the heart risks faced by women of similar age, the Hopkins researchers assert that tamoxifen should avert only about 13 heart attacks. They also suggest that, given the age of the recruits, the trial would likely prevent only 52 cases of breast cancer.

Furthermore, they say, data on endometrial cancer in tamoxifen users suggest that the drug probably triples -- rather than doubles -- the usual incidence of this malignancy. If so, then the trial might foster between 39 and 57 such uterine cancers, somewhat more than the 38 anticipated by the trial's designers.

Moreover, the Hopkins group points out that the designer's risk-benefit analysis included only anticipated deaths from blood clots. Given the potential for damage from even non-lethal clots -- which can cause strokes, for example -- these should also be part of any risk accounting. Bush and Helzlsouer argue. When the Hopkins researchers factored in nonlethal clots, they estimated that the cancer-prevention trial could achieve anything from a small net benefit (preventing eight more health problems than it induced) to a moderate negative effect (fostering 17 more problems than it prevented).

Finally, recent reports have linked tamoxifen use with eye toxicity (SN: 7/4/92, p.12). When Bush and Helzlsouer included such ophthalmic complications in the risk equation, they estimated that the trial would have a solidly negative impact, causing 31 to 57 more adverse outcomes than it prevented.
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Title Annotation:National Cancer Institute breast cancer prevention study criticized
Publication:Science News
Article Type:Brief Article
Date:Sep 25, 1993
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