Cancer of the Breast

Breast cancer is the most frequently diagnosed cancer in women in the United States, with a lifetime risk of 1 in 8. Age, family history, and exposure to hormones affect risk of developing breast cancer. Multiple risk-reduction approaches have been developed for patients at high risk, including chemoprevention, prophylactic surgery, behavioral modification, and enhanced surveillance. It is increasingly realized that breast cancer comprises multiple different diseases, including hormone receptor positive tumors, HER2 positive tumors, and tumors that lack expression of hormone receptors and HER2. Treatment of breast cancer is multidisciplinary, involving medical, radiation, and surgical oncologists, pathologists, and radiologists. Management approaches depend on the extent of disease at diagnosis, the pathologic characteristics of the tumor, and other factors including comorbidities and patient preferences. Surgical resection is either lumpectomy or mastectomy in combination with axillary assessment; the procedure performed depends on individual patient and tumor characteristics. Radiotherapy is an adjunct for most patients who undergo lumpectomy, and for a subset of high risk patients who undergo mastectomy. Multiple systemic treatment options are available, and selection of regimen depends on the patient and disease characteristics. Anti-endocrine therapies such as tamoxifen and aromatase inhibitors are used for chemoprevention and for treatment of patients with early stage or metastatic hormone receptor positive breast cancer. Cytotoxic chemotherapy, anti-HER2 therapy, and other targeted therapies are also incorporated into treatment regimens. Overall, most patients with breast cancer have excellent disease outcomes, although continued research is needed to find more effective therapies for treatment of metastatic disease.