A new study estimates that two million healthy women would benefit from taking tamoxifen as 'chemoprevention' for breast cancer. The analysis was done using a small sample of the U.S. population and a limited model of breast cancer risk. Essentially the study results are estimates based on estimates. The authors state that young women are most likely to benefit, but they fail to consider the long-term effects of tamoxifen on the health of women given tamoxifen for a five-year period (the recommended duration for cutting risk) at relatively young ages. They can't consider those effects, because they've never been studied.

Marketing pills for prevention encourages otherwise healthy women to subject themselves to serious side effects, including increased risk of blood clotting and endometrial cancer. True breast cancer prevention will only come from understanding and eradicating the causes of the disease.