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On September 24, 2013, the US Preventive Services Task Force announced new guidelines for the use of two drugs for preventing breast cancer in women. For women at low or average risk of the disease, however, side effects outweigh cancer prevention.

In 2011, the US National Cancer Institute released an online breast cancer risk assessment tool, which we have linked below. Primarily designed for women who live inside the United States, for which the National Cancer Institute has the most data, the online questionnaire computes a woman's risk of developing invasive breast cancer from answers to just nine questions. But only recently has the National Cancer Institute had suggestions for preventing breast cancer for women whom the online screening test finds high risk.

How high is "high risk" for breast cancer?

Women are considered "high risk" for invasive breast carcinoma if the model predicts chances of more than 1 in 60, or about 1.7%, of developing cancer over a 5-year period. By age 60, essentially all women are at high risk for breast cancer.

What does the model take into account when predicting cancer?

The Gail model, used to create the online questionnaire, considers a woman's age, race, family history of breast cancer, age at puberty, history of pregnancy, and personal history of breast exams to compute risk of developing the disease. The model can only predict the risk of cancer for women who are 35 or older, and because it's based on data collected in the USA, it may not be accurate for women who live in countries where breast cancer is rare, such as most of East Asia. 

The online risk assessment tool is not accurate for predicting recurrence of cancer in women who have already had it, and it's not 100% accurate. It should not be the only basis for making decisions about cancer, just a source of the right questions to discuss with the doctor.

If I am at high risk for breast cancer, is there anything I can do?

There are two drugs that sometimes prevent breast cancer, tamoxifen (Nolvadex) and raloxifene (Evista).

  • Tamoxifen has been used for over 20 years to stop the progression of breast cancer in women and as a treatment for breast cancer in men. The FDA approved it for stopping the contralateral breast cancer (spread of cancer from one breast to the other) and for the prevention of estrogen-related breast cancers in 2005.
  • Raloxifene reduces the density of the breast, essentially giving cancer less tissue to work with. The drug is also used to prevent osteoporosis, although many post-menopausal women who use it report that it increases the number and severity of hot flashes.

There are limitations in how well these drugs work. Because their mode of action is to make estrogen less available to cancer cells, they only prevent estrogen receptor-positive breast cancer. Tamoxifen increases the risk of blood clot formation and also increases the risk of cataracts as well as increasing the risk of endometrial cancer. Raloxifene also increases the risk of blood clotting, although not as much, and does not increase the risk of endometrial cancer. Both drugs may be more appropriate for women who have had hysterectomies.

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