National Cancer Institute

Probability of Breast Cancer in American Women

1. What is the average American woman’s risk of developing breast cancer?

   The National Cancer Institute’s (NCI) Surveillance, Epidemiology, and End Results (SEER) Program has published its SEER Cancer Statistics Review 1975–2007 (1). This report estimates that, based on current rates, 12.2 percent of women born in the United States today will develop breast cancer at some time in their lives. This estimate is based on breast cancer statistics for the years 2005 through 2007.

   This estimate means that, if the current rate stays the same, women born now have an average risk of 12.2 percent (often expressed as “1 in 8”) of being diagnosed with breast cancer at some time in their lives. On the other hand, the chance that they will never have breast cancer is 87.8 percent (expressed as “7 in 8”).

   In the 1970s, the lifetime risk of being diagnosed with breast cancer in the United States was just under 10 percent (often expressed as “1 in 10”).

   The last five annual SEER reports show these estimates of lifetime risk:

   • 13.2 percent for 2000 through 2002 (“1 in 7.58,” often expressed as “1 in 8”)
   • 12.7 percent for 2001 through 2003 (“1 in 7.87,” often expressed as “1 in 8”)
   • 12.3 percent for 2002 through 2004 (“1 in 8.13,” often expressed as “1 in 8”)
   • 12.0 percent for 2003 through 2005 (“1 in 8.33,” often expressed as “1 in 8”)
   • 12.1 percent for 2004 through 2006 (“1 in 8.26,” often expressed as “1 in 8”)

   SEER statisticians expect some variability from year to year. Slight changes, such as the one reported this year, may be explained by a variety of factors, including minor changes in risk factor levels in the population, slight changes in screening rates, or just random variability inherent in the data. 

2. What is the average American woman’s risk of being diagnosed with breast cancer at different ages?

   The estimated probability of being diagnosed with breast cancer for specific age groups and for specific time periods is generally more informative than lifetime probabilities. Estimates by decade of life are less influenced by changes in life expectancy and incidence rates. The SEER report estimates the risk of developing breast cancer in 10-year age intervals (1). These calculations factor in the proportion of women who live to each age. In other words, they take into account that not all women live to older ages, when breast cancer risk becomes the greatest.

   A woman’s chance of being diagnosed with breast cancer is:

   • from age 30 through age 39 . . . . . . 0.43 percent (often expressed as "1 in 233")
   • from age 40 through age 49 . . . . . . 1.45 percent (often expressed as "1 in 69")
   • from age 50 through age 59 . . . . . . 2.38 percent (often expressed as "1 in 42")
   • from age 60 through age 69 . . . . . . 3.45 percent (often expressed as "1 in 29")

   These probabilities are averages for the whole population. An individual woman’s breast cancer risk may be higher or lower, depending on a number of factors, including her family history, reproductive history, race/ethnicity, and other factors that are not yet fully understood. To calculate an individual’s estimated risk, see the Breast Cancer Risk Assessment Tool.

   Visit NCI’s Web site for more information about lifetime risk of breast cancer. 

Selected Reference

1. Altekruse SF, Kosary CL, Krapcho M, et al. SEER Cancer Statistics Review, 1975–2007. Bethesda, MD: National Cancer Institute, 2010.

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Related NCI materials and Web pages:

• BRCA1 and BRCA2: Cancer Risk and Genetic Testing Fact Sheet
• Mammograms Fact Sheet
• Understanding Breast Changes: A Health Guide for Women
• What You Need To Know About™ Breast Cancer

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