Chemoprevention: Drugs that can reduce breast cancer risk

Two drugs — tamoxifen (Nolvadex) and raloxifene (Evista) — now have official Food and Drug Administration (FDA) approval to help protect high-risk women from getting breast cancer.

Research is under way to determine if other drugs can do the job as well as or better than tamoxifen and raloxifene. Top on the list of potential breast cancer prevention drugs is a class of medications known as the aromatase inhibitors. Ongoing studies are evaluating the preventive effects of the aromatase inhibitors versus placebo in high-risk postmenopausal women.

Aromatase inhibitors

Aromatase inhibitors reduce estrogen levels in a woman's body by preventing an enzyme called aromatase from converting other hormones to estrogen. By reducing the amount of estrogen in your body, you deprive breast cancer cells of the fuel they need to grow and thrive. Aromatase inhibitors are only effective in postmenopausal women.

Three aromatase inhibitors are currently used to treat breast cancer in postmenopausal women: anastrozole (Arimidex), exemestane (Aromasin) and letrozole (Femara).

In a study of women who had estrogen receptor positive breast cancer and received standard treatment — surgery plus radiation therapy or chemotherapy — study participants were randomly assigned to take either tamoxifen or anastrozole in an attempt to prevent a recurrence of breast cancer. Study results show anastrozole was slightly better than tamoxifen in reducing the risk of recurrence. The risk of developing a new cancer in the other breast was also lower among women who took anastrozole than in those who took tamoxifen.

These promising results have led researchers to embark on a number of studies to evaluate the effectiveness of aromatase inhibitors in preventing breast cancer in high-risk postmenopausal women who haven't been diagnosed with breast cancer.

Aromatase inhibitors appear to be at least as effective as and possibly better than tamoxifen, with fewer side effects. Serious adverse effects, such as blood clots and uterine cancer, are less common with aromatase inhibitors. However, aromatase inhibitors may be more likely to contribute to bone fractures and the bone-thinning disease osteoporosis.

from:mayoclinic.com