4. Epidemiology, Risk Factors, and Prevention

Breast cancer is the most frequently diagnosed cancer in women in the United States, with an estimated 296,000 new cases and more than 40,000 deaths in 2013. Age, family history, and both endogenous and exogenous ovarian hormone exposure have important effects on risk and have been incorporated into models that predict individual risk of breast cancer; diet, alcohol use, and other factors play smaller roles. Inherited mutations in BRCA1, BRCA2, and CHEK2 play a role in the development of hereditary breast cancer, and high-risk individuals can be directly tested. BRCA mutation-associated breast cancer differs from sporadic breast cancer in that BRCA mutation carriers have a higher risk of breast and ovarian cancer and differential sensitivity to chemotherapeutic agents. As BRCA genetic testing is readily available, BRCA mutation status should be evaluated in high-risk women, including women who were diagnosed with breast cancer at an early age, who have a strong family history, or whose tumors were triple negative (TN). Given the high rate of contralateral breast cancer and ovarian cancer, mutation carriers with newly diagnosed breast cancer may choose to undergo contralateral prophylactic mastectomy or bilateral salpingo-oophorectomy. In addition, two selective estrogen receptor modulators, tamoxifen and raloxifene, and aromatase inhibitors can be used to decrease the incidence of invasive breast cancer in women who are at high risk of this condition.