Significance

Incidence and Mortality
Other Risk Factors

Breast cancer is the most common noncutaneous cancer in U.S. women, with an estimated 226,870 new cases of invasive disease (plus 63,300 cases of in situ disease) and 39,510 deaths in 2012.[1] 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 [2] and the United Kingdom [3] 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.[4] Similar findings have been documented in the United States. Mammographic screening has also increased the diagnosis of noninvasive cancers and premalignant lesions. Whereas ductal carcinoma in situ was a rare condition before 1985, it is currently diagnosed in more than 63,000 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).[2]

In 2012, an estimated 39,510 women will die of breast cancer, compared with about 72,590 women who will die of lung cancer.[1] Approximately one in six women diagnosed with breast cancer dies of the breast cancer, while nearly all women with lung cancer die of lung cancer.

Breast cancer mortality increases with age. For a 40-year-old woman without a breast cancer diagnosis, the chance of dying from breast cancer within the next 10 years is extremely small, but for a woman older than 65 years, it is about 1% (see Table 4). Women older than 70 years have an even higher risk of dying of breast cancer, but they are even more likely to die of other causes.[5]

Additional risk factors include a strong family history of breast or ovarian cancer (particularly first-degree relatives, on either the mother's or father's side); early age at menarche and late age at first birth (reflecting estrogen exposure); and a history of breast biopsies, especially for proliferative benign breast disease,[7,8] including radial scalloping lesions (a pathologic entity also called radial scars, even though unrelated to previous surgeries or scars).[9] The Gail model estimates individual risk over time based on these factors for women aged 40 years or older who receive regular mammography.[10-12] (Refer to the Breast Cancer Risk Assessment Tool.)

Women with a personal history of invasive breast cancer, ductal carcinoma in situ, or lobular carcinoma in situ have a 0.6% to 1.0% estimated annual risk of developing a new primary breast cancer.[13]

Women treated with thoracic radiation, especially when younger than 30 years, have a 1% annual risk of breast cancer, starting 10 years after the irradiation.[14]

Radiological breast density [15-17] is a strong risk factor for breast cancer and also presents challenges in the interpretation of mammograms. Dense fibroglandular tissue seen on mammography is associated with a threefold to sixfold increased risk of breast cancer compared with fatty breast tissue.

Behavioral factors such as menopausal hormone use, obesity, and alcohol intake are associated with an increased risk of breast cancer. (Refer to the PDQ summaries on Cancer Prevention Overview and Breast Cancer Prevention for more information.)

Breast cancer incidence and mortality risk also vary according to geography, culture, race, ethnicity, and socioeconomic status and are discussed more fully below (refer to the Special Populations section of this summary for more information).

References

1. American Cancer Society.: Cancer Facts and Figures 2012. Atlanta, Ga: American Cancer Society, 2012. Available online. Last accessed September 24, 2012. 
   
   
2. Altekruse SF, Kosary CL, Krapcho M, et al.: SEER Cancer Statistics Review, 1975-2007. Bethesda, Md: National Cancer Institute, 2010. Also available online. Last accessed July 31, 2012. 
   
   
3. Johnson A, Shekhdar J: Breast cancer incidence: what do the figures mean? J Eval Clin Pract 11 (1): 27-31, 2005.  [PUBMED Abstract]
   
   
4. Hemminki K, Rawal R, Bermejo JL: Mammographic screening is dramatically changing age-incidence data for breast cancer. J Clin Oncol 22 (22): 4652-3, 2004.  [PUBMED Abstract]
   
   
5. Kerlikowske K, Salzmann P, Phillips KA, et al.: Continuing screening mammography in women aged 70 to 79 years: impact on life expectancy and cost-effectiveness. JAMA 282 (22): 2156-63, 1999.  [PUBMED Abstract]
   
   
6. Schwartz LM, Woloshin S, Welch HG: Risk communication in clinical practice: putting cancer in context. J Natl Cancer Inst Monogr (25): 124-33, 1999.  [PUBMED Abstract]
   
   
7. London SJ, Connolly JL, Schnitt SJ, et al.: A prospective study of benign breast disease and the risk of breast cancer. JAMA 267 (7): 941-4, 1992.  [PUBMED Abstract]
   
   
8. McDivitt RW, Stevens JA, Lee NC, et al.: Histologic types of benign breast disease and the risk for breast cancer. The Cancer and Steroid Hormone Study Group. Cancer 69 (6): 1408-14, 1992.  [PUBMED Abstract]
   
   
9. Jacobs TW, Byrne C, Colditz G, et al.: Radial scars in benign breast-biopsy specimens and the risk of breast cancer. N Engl J Med 340 (6): 430-6, 1999.  [PUBMED Abstract]
   
   
10. Gail MH, Brinton LA, Byar DP, et al.: Projecting individualized probabilities of developing breast cancer for white females who are being examined annually. J Natl Cancer Inst 81 (24): 1879-86, 1989.  [PUBMED Abstract]
    
    
11. Bondy ML, Lustbader ED, Halabi S, et al.: Validation of a breast cancer risk assessment model in women with a positive family history. J Natl Cancer Inst 86 (8): 620-5, 1994.  [PUBMED Abstract]
    
    
12. Spiegelman D, Colditz GA, Hunter D, et al.: Validation of the Gail et al. model for predicting individual breast cancer risk. J Natl Cancer Inst 86 (8): 600-7, 1994.  [PUBMED Abstract]
    
    
13. Gail MH, Costantino JP, Bryant J, et al.: Weighing the risks and benefits of tamoxifen treatment for preventing breast cancer. J Natl Cancer Inst 91 (21): 1829-46, 1999.  [PUBMED Abstract]
    
    
14. Goss PE, Sierra S: Current perspectives on radiation-induced breast cancer. J Clin Oncol 16 (1): 338-47, 1998.  [PUBMED Abstract]
    
    
15. Ma L, Fishell E, Wright B, et al.: Case-control study of factors associated with failure to detect breast cancer by mammography. J Natl Cancer Inst 84 (10): 781-5, 1992.  [PUBMED Abstract]
    
    
16. Goodwin PJ, Boyd NF: Mammographic parenchymal pattern and breast cancer risk: a critical appraisal of the evidence. Am J Epidemiol 127 (6): 1097-108, 1988.  [PUBMED Abstract]
    
    
17. Fajardo LL, Hillman BJ, Frey C: Correlation between breast parenchymal patterns and mammographers' certainty of diagnosis. Invest Radiol 23 (7): 505-8, 1988.  [PUBMED Abstract]