Medications to Help Prevent Breast Cancer

David R Arbutina, MD, FACS

Many people that are considered high risk for breast cancer often wonder if there is something that they can take to help prevent the chances of getting the disease.  There are medications that are reported to lower a woman’s risk for breast cancer, but not the risk of dying from breast cancer.  How could this be?  The answer may be that the medications prevent the less aggressive cancers but not the aggressive cancers which are fatal.  These medications are a type of hormone therapy.  They work by blocking the effects of estrogen and progesterone.  In normal circumstances, these hormones play an important role in female health but, because estrogen stimulates breast cells it can also stimulate abnormal cells and cancers.

The main form of medication used in breast cancer prevention is a selective estrogen receptor modulator (SERM).  Medications of this type are tamoxifen, raloxifene, and toremifene.  Tamoxifen is approved in the United States for prevention of breast cancer and when given daily for five years, tamoxifen lowers the risk of developing breast cancer by about 2%.  However, tamoxifen also carries the risk of significant side effects which can be fatal.  (For this reason it is not approved for preventative use in Canada.)   Women are advised to consult with their physician to determine if they are at high risk for developing breast cancer and therefore a candidate for breast cancer prevention medication.  The benefits and risks must be weighed carefully because these drugs have significant risks.

For treatment of patients with invasive breast cancers, Tamoxifen and Arimidex have been shown to improve survival significantly so the benefit outweighs the risks.  However, for cancer prevention the risks and benefits must be considered carefully!