Breast Cancer

Should You Take an Anti-Breast-Cancer Drug?

Although there are a number of potent medicines to fight breast cancer, many women, even those at high risk for the disease, aren't taking advantage of them, according to experts from the Harvard Women's Health Watch newsletter.

An article in the January 2014 issue of the newsletter cited drugs that have become available in the last 20 years, including tamoxifen ( Nolvadex), raloxifene (Evista), and exemestane (Aromasin). Those medicines can reduce the odds of developing breast cancer for many high-risk women.

These drugs have been shown to prevent the occurrence of invasive and pre-invasive breast cancers," Dr. Paul Goss, director of breast cancer research at the Massachusetts General Hospital Cancer Center, told the newsletter. "It isn't just cancer that's prevented. It's precancer and abnormal mammograms. That leads to fewer biopsies." Part of the reluctance to take the drugs, the experts said, involves worry over possible side effects such as blood clots and an increased risk of uterine cancer.

But, Goss said in the article, the drugs have a long-established history of safety and effectiveness. Researchers have studied the effects of the drugs on breast-cancesr patients long before the medicines were considered for prevention. "Tens of thousands of women have taken these medications worldwide, so the side effect profiles are extremely well defined," Goss says.

He also said that the anti-breast cancer medicines are a harder sell because they don't show immediate, concrete effects like drugs to lower blood pressure or cholesterol.  "When you show a patient that their blood pressure today is lower than it was—that's a picture of triumph," Goss says. "It's why the patient is putting up with the side effects. I think that's the single biggest reason why breast cancer prevention hasn't prevailed."

All three drugs work against estrogen receptive positive breast cancer, the most common type of breast cancer, which needs estrogen to grow. Tamoxifen and raloxifene are classified as selective estrogen receptor modulators, or SERMs; extemestane is classified as an aromatase inhibitor.  Despite the drugs' advantages, though, the Harvard experts say, there's still a challenge in figuring out which women are the best candidates for the medication.