Breast cancer is the most commonly diagnosed nondermatologic cancer and the second leading cause of cancer-related deaths among women in the United States. In 1996, a total of 184,300 new cases of and 44,300 deaths from invasive breast cancer are projected among women. To assess trends in incidence and death rates for breast cancer among US women, the CDC analyzed national incidence data from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program and death-certificate data from the CDC's National Center for Health Statistics (NCHS).
This report presents incidence and death rates for breast cancer for 1992 (the most recent year for which SEER data were available) and summarizes trends in these rates for 1973 to 1992. Overall, these findings indicate that incidence rates for invasive breast cancer increased among women during 1973 to 1987 and stabilized during 1988 to 1992, while mortality remained stable during 1973 to 1988 and decreased during 1989 to 1992.
The incidence rate of breast cancer in the United States is estimated by using aggregate data reported by the SEER program, which includes a nonrandom sample of approximately 14% of the US population. Based on 1990 data from the Bureau of the Census, the demographic characteristics of persons included in SEER is representative of the total US population for whites and blacks; in addition, persons included in SEER reflect the percentage of persons among the total US population living below the poverty level* and the percentage of adults who graduated from high school. However, a higher proportion of persons included in SEER resided in urban areas.
This analysis includes all cases of invasive breast cancer (International Classification of Diseases, for Oncology, codes C50.0-C50.9) registered in SEER. Annual incidence rates were computed for 1973 to 1992, and race- and age-specific average annual incidence rates were computed for the combined years of 1988 to 1992.
Decedents for which the underlying cause of death was breast cancer (International Classification of Diseases, Adapted, Ninth Revision, codes 174.0-174.9) were identified from public-use mortality data tapes. Annual death rates were computed for 1973 to 1992, and race-specific average annual death rates by age and by state were computed for the combined years of 1988 to 1992.
Denominators for annual incidence and death rate calculations were derived from US census population estimates. Rates were directly standardized to the age distribution of the 1970 US population using 5-year age groupings. Data are presented only for whites and blacks because numbers for other racial/ethnic groups were too small for meaningful analysis.
Breast Cancer Incidence
In 1992, the overall age-adjusted incidence rate for breast cancer was 110.6 per 100,000 women. The rate for white women (113.1) was higher than that for black women (101.0).
During 1973 to 1992, the overall incidence rate increased from 82.5 to 110.6: rates increased steadily during 1973 to 1987 and stabilized during 1988 to 1992 (Figure 1). During 1988 to 1992, incidence rates increased directly with age until age 75 to 79 years for whites and age 80 to 84 years for blacks; the rates for whites and blacks were similar for women age less than 45 years, but for women age 45 years or more, the rate was higher for whites than for blacks. During 1973 to 1992, race-specific rates varied: for white women, the age-adjusted rate increased 34% (from 84.3 to 113.1) and, for black women, increased 47% (from 68.7 to 101.0).
Breast Cancer Mortality
In 1992, a total of 43,063 US women died from breast cancer. The death rate was 26.2 per 100,000 women.
During 1973 to 1992, the overall death rate varied; rates were stable during 1973 to 1988, before decreasing during 1989 to 1992 (Figure 1). During 1988 to 1992, the overall ratio of black-to-white death rates was 1.2. Rates increased directly with age. For women age less than 70 years, the rate was higher for blacks than for whites; for women age 70 years or more, the rate was higher for whites than for blacks. During this period, race-specific rates varied. During 1989 to 1992, the rate for white women decreased 6% (from 27.5 to 26.0) and, for black women, increased 3% (from 30.4 to 31.2).
During 1988 to 1992, the state-specific age-adjusted death rate ranged from 18.2 in Hawaii to 35.3 in the District of Columbia.
Editorial Note from the CDC
The findings in this report indicate that incidence rates for breast cancer increased 34% during 1973 to 1992. The increase and later stabilization of incidence rates during the 1980s is most likely related to increased use of breast cancer screening methods, particularly mammography and clinical breast examination, which enable earlier diagnosis of the disease.
The decrease in breast cancer death rates during 1989 to 1992 may reflect a combination of factors, including earlier diagnosis and improved treatment. For example, screening mammography and clinical breast examination are effective methods for reducing breast cancer mortality among women age 50 years or more. Survival from breast cancer increases when the disease is diagnosed at earlier stages, and from 1974-1976 to 1986-1991, the survival rate for invasive breast cancer increased substantially.
Differences in the race-specific and state-specific incidence and death rates for breast cancer during 1973 to 1992 may reflect differences in such factors as socioeconomic status, access to and delivery of medical care, and the prevalence of specific risks for disease. For example, women in minority populations are less likely than white women to be screened for breast cancer. Although socioeconomic and risk-factor data were not analyzed in this report, the findings underscore the need for further characterization of the burden of cancer for US women in racial/ethnic, geographic, and other subgroups.
Early detection and appropriate treatment are essential to reducing the burden of breast cancer in the United States. The CDC's National Breast and Cervical Cancer Early Detection Program provides early detection screening and referral services for cancers of the breast and cervix among older women who have low incomes or are uninsured, underinsured, or in a racial/ethnic minority. Additional efforts by this program and health-care professionals are needed to ensure that every US woman at risk for breast cancer receives breast cancer screening, prompt follow-up, and assurance that tests are conducted in accordance with current federal quality standards.
Adapted from Morbidity and Mortality Weekly Report, vol 45, no. 39, October 4, 1996.