Key Subtypes
Breast cancer encompasses multiple subcategories of disease based on tumor location and histology. The key molecular subtypes of invasive breast cancer include the following1:
Luminal: The most common subtype of breast cancer is luminal, comprising 60% to 70% of cases.1 Luminal breast cancer is characterized by high estrogen receptor (ER) expression and typically lacks human epidermal growth factor receptor 2 (HER2) overexpression. Luminal tumors are grouped into subtypes A and B on the basis of expression levels of proliferative or cell-cycle genes. Luminal B tumors are associated with overexpression of such genes.1
HER2+: Approximately 12% to 20% of breast tumors are HER2-enriched.1 These tumors typically exhibit overexpression of Erb-B2 and low ER expression by immunohistochemistry.1
Basal: The basal subtype comprises ~15% of all invasive breast cancers.1 Basal tumors often lack ER expression, are high-grade, and are large at the time of diagnosis, with a high rate of local and distant recurrence.1
Triple-negative breast cancer (TNBC): As many as 70% to 80% of TNBC tumors are basal.1 TNBC tumors lack protein expression of ER, HER2, and progesterone receptor.1
Incidence in the United States
Breast cancer is estimated to be the most common cancer diagnosis among women in the United States, with invasive female breast cancer rates increasing by ~0.5% per year since the mid-2000s.2 In 2023, an estimated 297,790 women and 2800 men were predicted to be diagnosed with invasive breast cancer.2 Breast cancer was expected to be the second deadliest cancer for women (behind lung cancer), with an estimated 43,170 deaths anticipated in 2023.2
Epidemiology in the United States
Approximately two-thirds of female breast cancers are localized (64%), and the remaining involve regional (29%) or distant (6%) metastases.3Although the 5-year survival rate is high for female patients with localized disease (99%), it is lower among those with distant metastases (30%).3
Risk Factors
Risk factors associated with breast cancer incidence include age, family history, BRCA mutations, menopausal hormone therapy, alcohol consumption, and physical inactivity.2 Reproductive and hormonal factors may also increase or mitigate risk of breast cancer.2
Unmet Need
Large racial inequalities in survival remain, as 5-year survival rates are 9% lower (in absolute terms) for Black women than for White women.2
References: 1. Johnson et al. J Breast Imaging. 2021;3:12-24. 2. American Cancer Society. Cancer Facts and Figures 2023. 3. National Cancer Institute. Surveillance, Epidemiology, and End Results Program. Cancer Stat Facts: Female Breast Cancer. https://seer.cancer.gov/statfacts/html/breast.html. Accessed September 1, 2022.
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