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Tamoxifen - the good and the bad.

Panacea or Pandora's box? Such was the question raised in a recent New England Journal of Medicine editorial about the possible negative effects of tamoxifen, a drug that for nearly 20 years has shown remarkable success in the treatment of breast cancer.

Used in conjunction with surgery and radiation, tamoxifen has been shown to reduce rates of recurrence and death, as well as the development of cancer in the other breast, among women over 50. Because the drug must be used for a long time (at least five years in many cases), many doctors are concerned that its antiestrogen effect may weaken bony structures, particularly the spine.

There is additional concern that the drug may affect other hormonal processes as well. The possibility that it may even cause other cancers has also been suggested.

A joint study by researchers at the University of Wisconsin and the Albert Einstein Medical Center in Philadelphia was reported in the same issue of the Journal. They found that a significant strengthening of spinal bone occurred in women treated with tamoxifen, whereas women in the control group, treated with a placebo, showed actual weakening of spinal bone.

Whether this favorable effect on spinal bone results in fewer fractures has yet to be shown, but it was certainly good news for women over 50 who are being treated with tamoxifen. In a previous study, these researchers had shown that the drug also favorably affects serum cholesterol levels, which may be related to the fact that women on tamoxifen therapy have a lower death rate from cardiovascular disease.

They also showed, however, that the drug can have undesirable side effects. Nearly half of the treated patients had hot flashes and vaginal dryness, compared with only 20 percent of the control group. About 10 percent of those treated stopped taking the drug within the first year because of unpleasant side effects.

A very small percentage of treated women - less than 2 percent - also had problems with blood clots. In another study, women undergoing long-term tamoxifen therapy appeared to have above normal rates of endometrial cancer, although none of these cases was fatal.

A new study will soon get under way to determine whether the drug might benefit healthy women who are at high risk for breast cancer (for example, those with a strong family history of the disease). Half of a randomly selected group of 16,000 such women will receive the drug while the other half receive a placebo.

The study will not only show whether the drug will prevent breast cancer in healthy women, but whether it also decreases death from cardiovascular diseases, helps to prevent fractures in postmenopausal women, and is safe.

"Only by careful evaluation under controlled circumstances will we be able to discover whether the administration of tamoxifen to healthy women is in fact the hoped-for panacea rather than the proverbial Pandora's box," concludes the editorial's author.

More than 100 trial centers around the country will be used for this study. Women more than 60 years of age may be eligible simply because getting older is a risk factor for breast cancer.

Risk factors for those under 50 include a family history of breast cancer, as well as early onset of menstruation, late first pregnancy, and late menopause. If you would like to participate in the trial, call the National Cancer Institute at 1-800-422-6237.
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Publication:Medical Update
Date:May 1, 1992
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