Ask Dr. K: Drugs may reduce breast cancer risk

DEAR DOCTOR K: My mother had breast cancer, so I believe I’m at higher risk than are most women. Should I take medication to prevent breast cancer?

DEAR READER: Without more details, I can’t give you a personal recommendation. But I can tell you about drugs that are available to prevent breast cancer and who, in general, should consider taking them.

There are different types of breast cancer. The most common type is “estrogen receptor-positive.” This type of breast cancer needs the hormone estrogen to grow.

Well-designed studies have shown that two drugs – tamoxifen and raloxifene – reduce the risk of ER-positive breast cancer. (Tamoxifen appears to be more effective than raloxifene.) These drugs are known as selective estrogen receptor modulators.

So far, so good. The problem is that SERMs can cause side effects, some serious. These include increased risk of blood clots and hot flashes. Tamoxifen also increases the risk of uterine cancer and cataracts. The question is: For which women do the benefits of these drugs outweigh the possible side effects?

Late last year, the U.S. Preventive Services Task Force issued guidelines on the subject. They recommended that physicians should offer to prescribe tamoxifen or raloxifene to women who are at high risk for ER-positive breast cancer and low risk for side effects.

Your doctor can estimate your breast cancer risk by taking several factors into account. These include your age, history of breast or ovarian cancer in a first-degree relative, and the age at which you first gave birth.

You can estimate your breast cancer risk with an online tool from the National Cancer Institute’s website: cancer.gov/bcrisktool. After you enter information about yourself, the tool gives you an estimate of your risk over the next five years, and over a lifetime.

In addition, women who are pregnant or planning to become pregnant, or who are currently breastfeeding, should generally avoid tamoxifen.