Epidemiology

Prevalence and Incidence of Breast Cancer1,2

  • It is estimated that there were more than 268,000 new cases of breast cancer in women in the United States (US) in 2019.1,4About 2670 new cases of invasive breast cancer will be diagnosed in American men in 2019.3,4
  • Breast cancer makes up 15.2% of all new cancer cases each year in the US.1
  • Approximately 12.8% of women will be diagnosed with breast cancer at some point during their lifetime, based on data from 2014 to 2016.1
  • There were 3,477,866 women living with breast cancer in the United States in 2016.1
  • Breast cancer accounts for 30% of all new cancer diagnoses in American women.4
  • The median age at diagnosis is 62 years, and the median age at death is 68 years.1

Survival Statistics1,2

  • It is estimated that over 41,000 women and about 500 men will die from breast cancer in the US in 2019.1,3,4
  • Breast cancer makes up 6.9% of all cancer deaths each year.1
  • The percentage of patients surviving 5 years or more after a diagnosis of breast cancer is 89.9%.1
  • The likelihood of surviving 5 years or more after a diagnosis of breast cancer depends on the stage of the cancer. The 5-year relative survival is 98.8% for women with localized cancer, 85.5% for those with regional cancer, and 27.4% for women with distant metastasizing cancer.1
  • While rates for new breast cancer cases have been rising an average of 0.3% each year for the last 10 years, death rates have been falling an average of 1.8% each year over the same period.1

Figure 1: Percent of Cases by Stage at Diagnosis: Female Breast Cancer1

Risk Factors for Breast Cancer

For an American woman, the lifetime risk of developing breast cancer is 1 in 8. Early detection of breast cancer remains the key to improving breast cancer outcomes and patient survival. A number of risk factors have been identified for the development of breast cancer.

  • Age. The strongest risk factor for breast cancer is age. Most breast cancers occur in women 50 years of age or older.1,2,4
  • Family history. Women with one first-degree relative (ie, mother, sister, or daughter) with breast cancer have twice the risk of developing breast cancer when compared with women who have no family history of breast cancer. That risk increases to fivefold or sixfold for women with two or more first-degree relatives with breast cancer.4,6
  • Personal history. The most common cancer among breast cancer survivors is breast cancer of the opposite breast.5
  • Genetic predisposition. Lifetime breast cancer risk ranges from 65% to 81% for carriers of the breast cancer gene 1 (BRCA1) mutation and from 45% to 85% for BRCA2 carriers. Other mutations such as TP53, PTEN, and STK11 have also been implicated in breast cancer development.6
  • Hormone exposure. Increased exposure to estrogen has been shown to increase the risk of breast cancer.8,9,10
    • Early menarche. Women who first begin menstruating before 13 years of age have a twofold increase in the risk of hormone receptor-positive tumors.
    • Parity. Women who have not given birth have an increased risk for developing breast cancer. Women who have their first child at a young age have a decreased risk of breast cancer: 20% risk reduction for a first birth at age 20 and 10% reduction for a first birth at 25 years of age. Women who have their first child at age 35 years have a 5% greater risk of developing breast cancer than women without children.
    • Breast feeding. One year of breast feeding may reduce the risk of breast cancer by 4.3%.
    • Age at menopause. A 1-year delay in the onset of menopause increases the risk of breast cancer by 3%, while a 5-year delay increases that risk by 17%.
    • Oral contraceptives. Use of oral birth control increases risk very slightly, ie, 5 more cases per 100,000 women. The small increase that occurs during use begins to taper off during the 10-year period after discontinuation.
  • Lifestyle factors. Alcohol consumption, lack of physical activity, obesity, and radiation exposure account for 21% of all breast cancers worldwide.11

 

REFERENCES

  1. National Cancer Institute (NCI). SEER Cancer Stat Facts. Female breast cancer. Available at https://seer.cancer.gov/statfacts/html/breast.html
  2. American Cancer Society (ACS). Breast Cancer Facts and Figures 2019-2020. Available at cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/breast-cancer-facts-and-figures/breast-cancer-facts-and-figures-2019-2020.pdf
  3. Key statistics for breast cancer in men. Available at www.cancer.org/cancer/breast-cancer-in-men/about/key-statistics.html
  4. Siegel RL, Miller KD, Jemal A. Cancer statistics, 2019. CA Cancer J Clin. 2019;69:7-34. Available at https://onlinelibrary.wiley.com/doi/epdf/10.3322/caac.21551
  5. Curtis RE, Freedman DM, Ron E, et al. New malignancies among cancer survivors: SEER cancer registries, 1973-2000. NCI, 2006. Available at https://seer.cancer.gov/archive/publications/mpmono/MPMonograph_complete.pdf
  6. Collaborative Group on Hormonal Factors in Breast Cancer. Familial breast cancer: collaborative reanalysis of individual data from 52 epidemiological studies including 58,209 women with breast cancer and 101,986 women without the disease. 2001;358:1389-1399. Abstract at www.ncbi.nlm.nih.gov/pubmed/?term=lancet%5Bta%5D+AND+2001%5Bdp%5D+AND+1389
  7. King MC, Marks JH, Mandell JB, et al. Breast and ovarian cancer risks due to inherited mutations in BRCA1 and BRCA2. 2003;302:643-646. Abstract at www.ncbi.nlm.nih.gov/pubmed/?term=king%5B1au%5D+AND+2003%5Bdp%5D+AND+643
  8. Rosner B, Colditz CA, Willett WC. Reproductive risk factors in a prospective study of breast cancer: the Nurses’ Health Study. Am J Epidemiol. 1994;139:819-835. Abstract at ncbi.nlm.nih.gov/pubmed/?term=rosner%5B1au%5D+AND+1994%5Bdp%5D+AND+819
  9. Collaborative Group on Hormonal Factors in Breast Cancer. Breast cancer and breastfeeding: collaborative reanalysis of individual data from 47 epidemiological studies in 30 countries, including 50302 women with breast cancer and 96973 women without the disease. 2002;360:187-195. Abstract at www.ncbi.nlm.nih.gov/pubmed/12133652
  10. Kelsey JL, Gammon MD, John EM. Reproductive factors and breast cancer. Epidemiol Rev. 1993;15:36-47. Abstract at ncbi.nlm.nih.gov/pubmed/?term=kelsey%5B1au%5D+AND+1993%5Bdp%5D+AND+36-
  11. Danaei G, Vander Hoorn S, Lopez AD, et al. Causes of cancer in the world: comparative risk assessment of nine behavioral and environmental risk factors. 2005;366:1784-1793. Available at www.thelancet.com/action/showPdf?pii=S0140-6736%2805%2967725-2
Clinical Care Toolkit Intro
Pathophysiology