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Epidemiology of Breast Cancer

This chapter presents a brief overview of the epidemiology of female breast cancer to provide estimates of the size and characteristics of the population at potential risk for cancer-related psychosocial distress. The characteristics of the population, such as cancer stage, a woman’s age at diagnosis, or her race and ethnicity, significantly affect disease prognosis, insurance status, and other circumstances, as well as emotional responses to breast cancer.

INCIDENCE AND MORTALITY

At birth, females face a one in eight chance that breast cancer will develop over a lifetime (American Cancer Society, 2002). In 2002, there were an estimated 203,500 new cases of invasive breast cancer (and 47,700 cases of ductal in situ cancer) among women (American Cancer Society, 2002). Excluding cancers of the skin, breast cancer is the most common cancer among American women, accounting for nearly one of every three cancers diagnosed. In 2002, there were an estimated 39,600 deaths from breast cancer. Only lung cancer causes more cancer deaths in women. Women believe they are more likely to get breast cancer than suffer a heart attack or develop diabetes (Avon Breast Cancer Foundation, 2002), despite the higher risk of these other conditions. To put the burden of breast cancer into perspective, 32 million women are living with cardiovascular disease and 513,000 women died of cardiovascular disease in 1999 (American Heart Association, 2002).



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Meeting Psychosocial Needs of Women with Breast Cancer 2 Epidemiology of Breast Cancer This chapter presents a brief overview of the epidemiology of female breast cancer to provide estimates of the size and characteristics of the population at potential risk for cancer-related psychosocial distress. The characteristics of the population, such as cancer stage, a woman’s age at diagnosis, or her race and ethnicity, significantly affect disease prognosis, insurance status, and other circumstances, as well as emotional responses to breast cancer. INCIDENCE AND MORTALITY At birth, females face a one in eight chance that breast cancer will develop over a lifetime (American Cancer Society, 2002). In 2002, there were an estimated 203,500 new cases of invasive breast cancer (and 47,700 cases of ductal in situ cancer) among women (American Cancer Society, 2002). Excluding cancers of the skin, breast cancer is the most common cancer among American women, accounting for nearly one of every three cancers diagnosed. In 2002, there were an estimated 39,600 deaths from breast cancer. Only lung cancer causes more cancer deaths in women. Women believe they are more likely to get breast cancer than suffer a heart attack or develop diabetes (Avon Breast Cancer Foundation, 2002), despite the higher risk of these other conditions. To put the burden of breast cancer into perspective, 32 million women are living with cardiovascular disease and 513,000 women died of cardiovascular disease in 1999 (American Heart Association, 2002).

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Meeting Psychosocial Needs of Women with Breast Cancer TABLE 2-1 Estimated Cancer Prevalence, United States, January 1, 1999   Number Percent Total 8,928,059 100.0 Sex   Male 3,929,515 44.0 Female 4,998,544 56.0 Site   Breast 2,051,280 23.0 Other 6,876,779 77.0 Years since breast cancer diagnosis   Total 2,051,280 100.0 0 to 4 724,510 35.3 5 to 9 495,499 24.2 10 to14 326,501 15.9 15 to 19 173,627 8.5 20+ 331,143 16.1   SOURCE: Ries et al., 2002. PREVALENCE In 1999, there were an estimated 2 million women with a history of breast cancer, representing 41 percent of the nearly 5 million female cancer survivors or 23 percent of 8.9 million total cancer survivors (Table 2-1). Among women with a history of breast cancer, 35 percent had been living with their diagnosis for less than 5 years, while 16 percent were survivors of 20 or more years. STAGE AT DIAGNOSIS The prognosis of invasive breast cancer is strongly influenced by the stage of the disease, or how far the cancer has spread when it is first diagnosed. Local stage describes cancer confined to the breast, regional stage tumors have spread to the lymph nodes, and distant stage cancers have metastasized (spread to distant sites) (American Cancer Society, 2001). As shown in Figure 2-1, the 5-year survival rate is highest for early stage cancer (96.4 percent), and lower for regional stage (77.7 percent) and distant stage (21.1 percent) cancer (American Cancer Society, 2001). Most breast cancer (63 percent) is localized at diagnosis, but this varies by race (see discussion below). Fewer women are diagnosed with regional (28 percent) or distant (6 percent) disease. Other women are diagnosed with noninvasive cancer that has not spread beyond its site of origin. These so-called in situ breast cancers are either lobular (originating in the breast

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Meeting Psychosocial Needs of Women with Breast Cancer FIGURE 2-1 Female breast cancer, United States, 1992–1997. *Survival rates are based on follow-up of patients through 1997. American Cancer Society, Surveillance Research, 2001. DATA SOURCE: NCI Surveillance, Epidemiology, and End Results Program, 2001. tissue made up of glands for milk production) or ductal (originating in the ducts that connect lobules to the nipple). In situ breast cancers affect approximately 54,300 women (47,700 ductal carcinoma in situ) each year in addition to the 203,500 invasive breast cancer cases diagnosed (American Cancer Society, 2002). The majority of these tumors will not become invasive. Most oncologists believe that lobular carcinoma in situ is not a true cancer, but is instead a marker of increased risk for developing future invasive cancer (American Cancer Society, 2001). SOME RISK FACTORS ASSOCIATED WITH BREAST CANCER Age The risk of breast cancer and death from breast cancer increases sharply with age for both white and African American women (Figure 2-2) (American Cancer Society, 2001). Breast cancer is predominantly a disease of older women, with 45 percent of incident cases and 59 percent of breast cancer deaths occurring among women age 65 and older (see Figure 2-3 below; Ries et al., 2002). Race and Ethnicity The incidence of breast cancer is higher among white as compared to African American women. By age, the rates among white and African

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Meeting Psychosocial Needs of Women with Breast Cancer FIGURE 2-2 Female breast cancer. Age-specific incidence and death rates, by race, United States, 1994–1998. American Cancer Society, Surveillance Research, 2001. DATA SOURCES: NCI Surveillance, Epidemiology, and End Results Program, 2001, and National Center for Health Statistics, 2001. FIGURE 2-3 Age distribution of breast cancer incident cases and deaths, 1995-1999. SOURCE: Ries et al., 2002.

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Meeting Psychosocial Needs of Women with Breast Cancer American women are similar until age 50 and then begin to diverge (Figure 2-2). The breast cancer mortality rate is higher among African American as compared to white women (Figure 2-4). The incidence and mortality rates for breast cancer are generally lower among women of other racial and ethnic groups (i.e., Asian and Pacific Islanders, American Indians, Hispanics) as compared to white and African American women (Figure 2-4) (American Cancer Society, 2001). When analyzed by race, survival is more favorable at each stage for white as compared to African American women (Figure 2-1). African American women are more likely than white women to be diagnosed when their cancer is at an advanced stage (e.g., 9 versus 6 percent with distant stage cancers). This later stage at diagnosis, in part, explains the overall poorer survival of African American as compared to white women with breast cancer (72.0 versus 87.0 percent surviving 5 years). Just over half of the survival difference can be attributed to the later stage at detection and tumors that are more aggressive and less responsive to treatment. The presence of additional illnesses and various sociodemographic factors (e.g., lack of health insurance) also contribute to the observed differences in survival between African Americans and whites FIGURE 2-4 Female breast cancer incidence and mortality rates,a by race and ethnicity, United States, 1992–1998. American Cancer Society, Surveillance Research, 2001. DATA SOURCES: NCI Surveillance, Epidemiology, and End Results Program, 2001, and National Center for Health Statistics, 2001. †Persons of Hispanic origin may be of any race. aRates are age-adjusted to the 1970 U.S. standard population.

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Meeting Psychosocial Needs of Women with Breast Cancer (American Cancer Society, 2001). A recent literature review of clinical trials and retrospective studies in the United States that compared survival between white women and African American women with breast cancer found that socioeconomic status replaces race as a predictor of worse outcome in many studies (Cross et al., 2002). According to this review, relative to white women, African American women were more likely to be diagnosed at a younger age and with more advanced disease that appeared to be more aggressive biologically. SUMMARY Breast cancer represents a significant health burden to American women. In 2002 there were an estimated 203,500 diagnoses of invasive breast cancer and 39,600 deaths. There are over 2 million women alive with a history of breast cancer. Age is a key risk factor associated with breast cancer, with 45 percent of new cases and 59 percent of deaths occurring among women age 65 and older. Most women (63 percent) are diagnosed with localized breast cancer that has a very favorable prognosis. Their 5-year survival was 96 percent, although some of these same women will eventually develop or have already developed recurrences. Although African American women are less likely to be diagnosed with breast cancer, when they are diagnosed, they are more likely to be diagnosed with regional or distant disease that has a less favorable prognosis. Other racial and ethnic groups (i.e., Asian and Pacific Islanders, American Indians, and Hispanics) have both lower breast cancer incidence and mortality rates. REFERENCES American Cancer Society. 2001. Breast Cancer Facts & Figures 2001–2002. Atlanta: American Cancer Society. American Cancer Society. 2002. Cancer Facts & Figures 2002. Atlanta: American Cancer Society. American Heart Association. 2001. 2002 Heart and Stroke Statistical Update. Dallas: American Heart Association. Avon Breast Cancer Foundation. 2002. Women’s Health Index 37. Cross CK, Harris J, Recht A. 2002. Race, socioeconomic status, and breast carcinoma in the U.S: What have we learned from clinical studies. Cancer 95(9):1988–1999. Ries LAG, Eisner MP, Kosary CL, Hankey BF, Miller BA, Clegg L, Edwards BK, eds. 2002. SEER Cancer Statistics Review, 1973–1999. Bethesda, MD: National Cancer Institute.