What is the average American woman’s risk of developing breast cancer during her lifetime?

Based on current incidence rates, 12.4 percent of women born in the United States today will develop breast cancer at some time during their lives (1). This estimate, from the most recent SEER Cancer Statistics Review (a report published annually by the National Cancer Institute’s [NCI] Surveillance, Epidemiology, and End Results [SEER] Program), is based on breast cancer statistics for the years 2007 through 2009.

This estimate means that, if the current incidence rate stays the same, a woman born today has about a 1 in 8 chance of being diagnosed with breast cancer at some time during her life. On the other hand, the chance that she will never have breast cancer is 87.6 percent, or about 7 in 8.

In the 1970s, the lifetime risk of being diagnosed with breast cancer in the United States was just under 10 percent (or about 1 in 10).

The last five annual SEER reports show the following estimates of lifetime risk of breast cancer, all very close to a lifetime risk of 1 in 8:

• 12.7 percent for 2001 through 2003
• 12.3 percent for 2002 through 2004
• 12.0 percent for 2003 through 2005
• 12.1 percent for 2004 through 2006
• 12.4 percent for 2005 through 2007

SEER statisticians expect some variability from year to year. Slight changes, such as the ones observed over the last 5 years, may be explained by a variety of factors, including minor changes in risk factor levels in the population, slight changes in breast cancer screening rates, or just random variability inherent in the data.

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

Many women are more interested in the risk of being diagnosed with breast cancer at specific ages or over specific time periods than in the risk of being diagnosed at some point during their lifetime. Estimates by decade of life are also less affected by changes in incidence and mortality rates than longer-term estimates. The SEER report estimates the risk of developing breast cancer in 10-year age intervals (1). According to the current report, the risk that a woman will be diagnosed with breast cancer during the next 10 years, starting at the following ages, is as follows:

• Age 30 . . . . . . 0.44 percent (or 1 in 227)
• Age 40 . . . . . . 1.47 percent (or 1 in 68)
• Age 50 . . . . . . 2.38 percent (or 1 in 42)
• Age 60 . . . . . . 3.56 percent (or 1 in 28)
• Age 70 . . . . . . 3.82 percent (or 1 in 26)

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 known factors (see Question 3) and on factors that are not yet fully understood. To calculate an individual woman’s estimated risk, health professionals can use the Breast Cancer Risk Assessment Tool.

For more information about risk of breast cancer at specific ages and for specific time periods, see Table 4.18 in the SEER report.