Incidence and Mortality
Breast cancer is the most common noncutaneous cancer in U.S. women, with an estimated 230,480 new cases of invasive disease (plus 57,650 cases of in situ disease) and 39,520 deaths in 2011. Males account for 1% of breast cancer cases and breast cancer deaths (refer to the Special Populations section of this summary for more information).
Ecologic studies from the United States  and the United Kingdom  demonstrate an increase in breast cancer incidence during the last three decades, rising from 82 cases per 100,000 people in 1973 to 124 per 100,000 in 2007. Between 1970 and the early 1980s the increase was small and has been attributed to changes in reproductive behavior and hormone use. Since the mid-1980s, with the widespread adoption of screening mammography, the increase has been dramatic. By illustration, the incidence among British women aged 50 to 65 years nearly doubled between 1984 and 1994. Similarly, in Sweden, where more cancers are discovered in younger women, the incidence of breast cancer increased dramatically in counties that adopted screening. Similar findings have been documented in the United States. Mammographic screening has also increased the diagnosis of noninvasive cancers and premalignant lesions. Whereas ductal carcinomain situ was a rare condition before 1985, it is currently diagnosed in more than 54,000 American women per year (refer to the Ductal Carcinoma In Situ section of this summary for more information).
One might expect that screening will identify many cancers before they cause clinical symptoms, followed by a subsequent compensatory decline in cancer rates, seen either in annual population incidence rates or in incidence rates in older women. So far, no compensatory drop in incidence rates attributable to a change in screening patterns has been observed. This raises concerns about overdiagnosis-screening that identifies clinically insignificant cancers (refer to the Overdiagnosis section of this summary for more information).
The risk of breast cancer depends on age (see Table 3). As shown in Table 3, the interval risk increases with starting age. Thus, a 60-year-old woman has a higher risk of being diagnosed with breast cancer in the next 10 years compared with a 40-year-old woman. Breast cancer is rare among younger women; among women aged 30 years, 4 in 1,000 will develop breast cancer in the next 10 years.
The cumulative lifetime risk decreases across the age groups as shown in Table 3. This is because a woman who is aged 50 years has lived through some of her risk period without having cancer. The common risk cited that one in eight women will develop breast cancer is based on lifetime risk starting from birth and does not account for the woman's current age. For example, women who are aged 60 years have lived a good portion of their life expectancy without cancer, therefore their remaining lifetime risk is less than for women who are aged 30 years (91 per 1,000 vs. 123 per 1,000).