A pill called anastrozole can reduce a woman’s likelihood of developing breast cancer by almost half, according to a recent study published in the Lancet medical journal and reported by NBC News.

For the study, researchers looked at more than 3,800 post-menopausal women from 18 countries between ages 40 and 70. All women included in the trial were considered at high risk of breast cancer. (This means the women had either two or more family members who had a history of the disease, a mother or sister who had breast cancer by the age of 50 or a close relative who had cancer in both breasts.) In addition, scientists also considered women with certain high-risk benign breast tumors.

During the study, researchers gave half of the women an anastrozole pill and half a placebo (a dummy pill). After five years, 2.8 percent of women who took the drug developed breast cancer, while those who took the placebo got breast cancer at a rate of 5.6 percent. (Statistically, this means that anastrozole contributed to a risk reduction of 53 percent for the disease.)

According to the report, this reduction was larger than those for tamoxifen or raloxifene, two commonly prescribed breast cancer treatment drugs. “Therefore, anastrozole is an attractive option for postmenopausal women at increased risk of breast cancer,” researchers said.

Anastrozole is an aromatase inhibitor, a class of drugs that basically turn the hormone estrogen all the way off to prevent cancer from forming in vulnerable breast tissue. The new drug has also been shown to have far fewer side effects, such as fatigue, blood clots and aches and pains, compared with previous preventive breast cancer treatments.

Breast cancer doctors in Britain and the United States have supported using anastrozole to treat women who are predisposed to the disease. They feel that anastrozole is safer and more effective, widely available and possibly cheaper because the drug is available as a generic (under the name Arimidex).

Black women are far more likely to die from breast cancer than their white counterparts. Click here to find out why.