A 26 percent increase in the probability of getting cancer is not as scary as it sounds, since the base-line probability of getting breast cancer by age 40 is relatively small.
The American Cancer Society estimates that today the probability of a 35-year-old American woman developing breast cancer by age 40 is 0.3 percent (or 1 in 336). A woman's probability at birth for developing breast cancer by age 40 is 0.48 percent (or 1 in 210). These estimates are based on the most recent data available, from 2001 to 2003.
For a more general perspective on breast cancer risk, the ACS provides the following data, also from 2001 to 2003: