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Epidemiology and Diagnosis

Breast cancer…

  • is the most common cancer in US women aside from skin cancers
  • accounts for about 30% of all new cancers in women each year
  • mainly occurs in middle-aged and older women (median age at diagnosis is 62 years)
  • is the second leading cause of cancer death in women (behind lung cancer). The chance that any woman will die from breast cancer is about 1 in 40 (~2.5%)1

2024 American Cancer Society estimates:

  1. ~310,720 new cases of invasive breast cancer. 
  2. ~56,500 new cases of ductal carcinoma in situ (DCIS).  
  3. ~42,250 deaths from breast cancer.
  4. The average risk of a woman in the US developing breast cancer sometime in her life is about 13%.1

However, there are reasons for optimism:

  • Breast cancer death rates have been decreasing steadily since 1989.
  • The declining death rate has been attributed to improved screening and awareness, along with improved treatments.
  • At this time there are more than 4 million breast cancer survivors in the United States.1

Most common breast cancer symptoms:

The most common breast cancer symptoms include:

  • Presence of a lump or thickening (a mass, swelling, skin irritation, etc) within or near the breast and in the underarm area as well
  • Differences/changes in the shape or size of a breast
  • Any changes in color or feel of the skin of the breast, areola, or nipple (eg, red, swollen, dimpled, puckered, etc)
  • Changes in the nipple (eg, tenderness, discharge, inversion, erosion, color change)

Subtypes: Understanding HR and HER2:

HR stands for hormone receptor. HR+ means that tumor cells have receptors for the hormones estrogen or progesterone, which can promote the growth of HR+ tumors. HER2 stands for human epidermal growth factor receptor 2. HER2+ means that tumor cells make high levels of a protein called HER2/neu, which has been shown to be associated with certain aggressive types of breast cancer.2

Generally, breast cancer is divided into 5 major common clinical subtypes based on estrogen receptor (ER) expression, progesterone receptor (PR) expression, and HER2 expression or gene amplification.3 These 5 subtypes are the following:

(a) HR+/HER2− (ie, tumors expressing ER, PR, or both) that are HER2-negative
(b) HR+/HER2+ (ER+/PR−/HER2+, ER−/PR+/HER2+, and triple-positive [ER+/PR+/HER2+] disease)
(c) HR−/HER2+
(d) HR−/HER2− (or triple-negative: ER−/PR−/HER2−)
(e) HER2-low, defined as immunohistochemical detection of HER2 protein at a 1+ or 2+ level in tumor cells, and lacking amplification of the gene encoding HER2, encompassing both HR+ and HR− patients 

Tumors classified as HR+/HER2− include those that are HER2-low and are the most common subtype, accounting for around 70% of all breast cancers.3 However, this rate appears to be increasing, with around 90% of new cases from 2017 to 2021 being HR+/HER2−.2 

References

  1. American Cancer Society. Key statistics for breast cancer. https://www.cancer.org/cancer/types/breast-cancer/about/how-common-is-breast-cancer.html.
  2. National Institutes of Health (NIH). Cancer stat facts: female breast cancer subtypes.
    https://seer.cancer.gov/statfacts/html/breast-subtypes.html.
  3. Pegram M, Pietras R, Dang CT, et al. Evolving perspectives on the treatment of HR+/HER2+ metastatic breast cancer. Ther Adv Med Oncol. 2023;15:17588359231187201.

Epidemiology and Diagnosis

Living With Breast Cancer

Treatment and Management

The Breast Cancer Care Team

FAQs

Reading and Resources

This activity is provided by Med Learning Group.
This activity is supported by an educational grant from Lilly.
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