A medication that keeps breast cancer from returning also seems to prevent it in the first place. Aromasin is a powerful anti-estrogen compound. It works by blocking an enzyme called aromatase used by the body in the production of estrogen. The study included more than 4,500 post-menopausal women who were at high risk of developing breast cancer. The women were randomly assigned to get Aromasin or a placebo.
In the course of the three-year study, 11 women taking Aromasin developed breast cancer. That compares to 32 of the volunteers on placebo. The relative risk reduction is large, about 65 percent. But because there were so many women involved and so few of them got breast cancer, the absolute risk went down from 1.4 percent of those on placebo to 0.5 percent of those on Aromasin. This works out to 94 women taking the drug for 3 years in order to protect one from breast cancer. Some doctors doubt that women will be willing to make that trade off, especially since Aromasin can cause hot flashes, joint pain, hair loss, fatigue and weakened bones.
[New England Journal of Medicine, online June 4, 2011]
The People's Perspective on Medicine