Besides being female, age is the most important risk factor for breast cancer. Table 5 shows a woman’s risk of being diagnosed with breast cancer at different ages. These probabilities are averages for the whole population. A woman’s breast cancer risk may be higher or lower depending on her personal risk factors and other factors not yet fully understood.  Currently, a woman living in the US has a 12.15%, or a 1 in 8, lifetime risk of being diagnosed with breast cancer. In the 1970s, the lifetime risk of being diagnosed with breast cancer was 1 in 11.  This increase in the likelihood of being diagnosed with breast cancer is due to longer life expectancy, as well as increases in breast cancer incidence due in part to changes in reproductive patterns, menopausal hormone use, the rising prevalence of obesity, and increased detection through screening. Lifetime risk reflects an average woman’s risk over an entire lifetime, including the possibility that she may die from another cause before she would have developed breast cancer, and should not be confused with risk over a shorter time period.

Table 5. Age-specific Probabilities of Developing
Invasive Female Breast Cancer*
The probability of
If current developing breast cancer

age is … in the next 10 years is: or 1 in:
20yr old –  0.06% or 1:1,681
30yr old –  0.43% or 1:232
40yr old –  1.45% or 1:69
50yr old –  2.38% or 1:42
60yr old –  3.45% or 1:29
70yr old –  3.74% or 1:27
Lifetime risk 12.15% or 1:8
*Among those free of cancer at beginning of age interval. Based on cases diagnosed 2005-2007. Percentages and ”1 in” numbers may not be numerically equivalent due to rounding.
Probability derived using NCI DevCan Software, Version 6.5.0.
American Cancer Society, Surveillance Research, 2011


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