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KEY CONCEPTS

  • A multidisciplinary approach is of upmost importance, especially with regard to planning and coordinating multimodality therapy. It is important to involve surgical and radiation oncology colleagues early to determine the best treatment plan.

  • Choice of systemic therapy is ultimately guided by biomarker status of the patient's tumor.

  • Whereas patients with hormone receptor–positive cancers should receive endocrine therapy, those with human epidermal growth factor receptor 2 (HER2)–positive cancers should receive anti-HER2 targeted therapy.

  • Genomic assays can help assess the benefit of adjuvant chemotherapy in patients with hormone receptor–positive/HER2-negative breast cancer.

  • All women with node-positive disease and a significant percentage of women with node-negative tumors that are hormone receptor negative or larger than 1 cm in size benefit from chemotherapy. Those with HER2-positive breast cancer need to receive anti-Her2 therapy

  • Chemotherapy is the cornerstone of treatment for patients with triple-negative breast cancer (TNBC).

  • Preoperative or neoadjuvant chemotherapy should be administered in most patients with HER2-positive or TNBC. The presence of a pathological complete response or residual disease has important prognostic implications but now allows us to identify patients that will benefit from additional adjuvant treatment.

EPIDEMIOLOGY

Incidence

Breast cancer is the second most common cause of death for U.S. women with an age-adjusted death rate of 20.3 per 100,000. In 2020, it is estimated that 276,480 American women will be diagnosed with breast cancer and that 42,170 will die from this disease, making breast cancer the third most common cause of cancer-related morality for all people in the United States, with lung cancer being the most common.1

In the early 1980s, the rates of breast cancer diagnosis rose sharply, likely related to increased mammographic screening, because it was the incidence of stage 0 and I carcinomas that rose most sharply. Data from the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute demonstrate that although the incidence of breast cancer later stabilized by the end of the 1980s, there has been an increase in the percentage of breast cancers that are hormone receptor positive. This is thought to be caused by either changes in receptor assays or an increased use of hormone replacement therapy by women.2,3 The incidence of primary breast cancer then decreased around 2003, shortly after the publication of the Women's Health Initiative (WHI) results, which prompted many healthy postmenopausal women to stop using hormone replacement therapy.4

Breast cancer incidence has long varied in different regions of the world. Its incidence is highest in Northern Europe and North America and lowest in Asia and Africa. Data suggest that this variability is caused not only by environmental factors but also to lifestyle. This is supported by the observation that breast cancer incidence is higher in second-generation Asian immigrants in the United States.5

Mortality

Breast cancer overall mortality rates had been ...

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