Researchers say women who have a strong family history of breast cancer may benefit from a drug called Anastrozole.
"There are millions of women who could benefit from a drug such as Anastrozole in reducing the risk of ever developing breast cancer," said Dr. Therese Bevers of the Anderson Cancer Center.
In a study of nearly 4,000 high-risk, post-menopausal women, those who took the pill for 5 years were half as likely to develop breast cancer then women on a placebo.
While this included invasive tumors, there was no difference in overall mortality rates.
Experts say this is an important addition to medications women already have for preventing cancer and may be more effective than Tamoxifen, with fewer side effects.
"Some of the side effects that were seen with Anastrozole in this trial were largely musculoskeletal problems and hot flashes, however these were really quite rare," explained Bevers.
In the study, which was partially paid for by drug makers, Anastrozole cut the incidence of breast cancers from 4- to 2-percent over 5 years.
It works by preventing the body from making estrogen, the fuel for many breast cancers.
Breast cancer is one of the biggest cancer killers of women in the U.S, second only to lung cancer.
The drug is available in generic form which may make it cheaper.
It's been used for years to treat some women already diagnosed with the disease in the U.S.
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