Estimating Breast Cancer Risk: Questions and Answers

Quick GuideBreast Cancer Diagnosis and Treatment

Breast Cancer Diagnosis and Treatment

6. What are some of the latest research findings on breast cancer risk?

Two studies in the September 6, 2006, issue of the Journal of the National Cancer Institute identified breast density as an important risk factor.* In one, a study of 11,638 women diagnosed with breast cancer, researchers identified different sets of risk factors in pre- and post-menopausal women. For pre-menopausal women, the risk factors included age, breast density, family history of breast cancer, and prior cancer diagnosis. For post-menopausal women, the risk factors included ethnicity, body mass index, age at natural menopause, use of hormone therapy, and a prior false-positive mammogram, in addition to all the risk factors for pre-menopausal women. The two separate models in this study for predicting breast cancer in pre- and post-menopausal women may be particularly helpful in identifying women at high risk for breast cancer.

The other study adds breast density and weight to the Gail model, a model that is the basis for the Breast Cancer Risk Assessment Tool (see Question 2). As before, the new model can be used to project risk over 5, 10, 20 and 30 year intervals. The new model predicted higher risks than the previous model in women with high breast density, and previous analyses indicated that the new model had modestly higher accuracy. Independent validation studies are needed before this model should be used for counseling, and before making a permanent change to the Breast Cancer Risk Assessment Tool.

7. Are there ways to decrease the chance of developing breast cancer?

Launched in April 1992, the Breast Cancer Prevention Trial (BCPT) was designed to see whether the drug tamoxifen could prevent breast cancer in women with an increased risk. Data reported in 1998 showed that both pre- and post-menopausal women taking tamoxifen had 49 percent fewer diagnosed cases of breast cancer. These results were also the first clear indication that a chemopreventive agent could be effective in preventing cancer in a high-risk population. For women over 50, tamoxifen was associated with serious side effects, such as endometrial cancer and blood clots. (

Starting in 1999, postmenopausal women ages 35 or older at increased risk for breast cancer participated in the Study of Tamoxifen and Raloxifene (STAR). The study compared tamoxifen with raloxifene, an osteoporosis drug. The initial results of the trial were announced on April 17, 2006 (see, and showed that the drug raloxifene works as well as tamoxifen in reducing breast cancer risk for postmenopausal women at increased risk of the disease. In STAR, both drugs reduced the risk of developing invasive breast cancer by about 50 percent. In addition, within the study, women who were prospectively and randomly assigned to take raloxifene daily, and who were followed for an average of about four years, had 36 percent fewer uterine cancers and 29 percent fewer blood clots than the women who were assigned to take tamoxifen. Uterine cancers, especially endometrial cancers, are a rare but serious side effect of tamoxifen. Both tamoxifen and raloxifene are known to increase a woman's risk of blood clots. Data from STAR continues to be analyzed. (

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