If a pill could prevent you from developing breast cancer, should you take it? A new study weighs the risks against the benefits of several drugs designed to prevent invasive breast cancer in women who are at high risk, including tamoxifen and raloxifene and tibolone. The side effects of these drugs may include cataracts, cancer of the uterine lining and blood clots, which could lead to heart attack or stroke.

The researchers, led by Dr. Heidi Nelson,at the Oregon Health & Science University, conducted a study on high-risk women to determine whether the effectiveness of preventing cancer outweighed the risk serious side effects that could occur. They found that the drug decreased invasive breast cancer by 30-68 percent, depending on the drug. This means a large number of women at risk could significantly cut their chances of developing breast cancer. But the researchers also found that women who took tamoxifen increased their risk of blood cots, cataracts and endometrial cancer. Tibolon was found to increase the risk of stroke more than the other two drugs.

The authors of the study are hoping to do conduct more research on the drugs in the near future to get a better sense of their effectiveness. Some doctors believe that not enough women are taking the drugs. Dr. Christy Russell, chair of the breast cancer advisory committee for the American Cancer Society, stated that “we have 200,000 new cases of breast cancer every year and we could potentially reduce that number by half using drugs that are already approved by the Food and Drug Administration for this purpose.” Russell suggested that women who have a family history of breast cancer or have been diagnosed with breast conditions that put them at a high risk of developing breast cancer, discuss the potential pros and cons of the drugs with their doctors.