Corresponding author: Lisa C. Richardson, email@example.com
Breast cancer death rates among women decreased during 2010-2014, but racial differences persisted, according to a study by the Centers for Disease Control and Prevention (CDC) in this week’s Morbidity and Mortality Weekly Report.
Breast cancer continues to be the most commonly diagnosed cancer and the second leading cause of cancer deaths among U.S. women (1). Compared with white women, black women historically have had lower rates of breast cancer incidence and, beginning in the 1980s, higher death rates (1). This report examines age-specific black-white disparities in breast cancer incidence during 1999–2013 and mortality during 2000–2014 in the United States using data from United States Cancer Statistics (USCS) (2). Overall rates of breast cancer incidence were similar, but death rates remained higher for black women compared with white women. During 1999–2013, breast cancer incidence decreased among white women but increased slightly among black women resulting in a similar average incidence at the end of the period. Breast cancer incidence trends differed by race and age, particularly from 1999 to 2004–2005, when rates decreased only among white women aged ≥50 years. Breast cancer death rates decreased significantly during 2000–2014, regardless of age with patterns varying by race. For women aged ≥50 years, death rates declined significantly faster among white women compared with black women; among women aged <50 years, breast cancer death rates decreased at the same rate among black and white women. Although some of molecular factors that lead to more aggressive breast cancer are known, a fuller understanding of the exact mechanisms might lead to more tailored interventions that could decrease mortality disparities. When combined with population-based approaches to increase knowledge of family history of cancer, increase physical activity, promote a healthy diet to maintain a healthy bodyweight, and increase screening for breast cancer, targeted treatment interventions could reduce racial disparities in breast cancer.
USCS includes incidence data from the CDC’s National Program of Cancer Registries (NPCR) and the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) Program and mortality data from the National Vital Statistics System (2). Data on new cases of invasive (malignant) breast cancer* diagnosed during 1999–2013 were obtained from population-based cancer registries affiliated with NPCR or SEER programs in each state and the District of Columbia (DC). Incidence data in this report met USCS publication criteria, covering 99% of the U.S. population during 2009–2013 and 92% during 1999–2013.† SEER Summary Stage 2000§ was used to characterize cancers as localized, regional, distant, or unknown stage using clinical and pathologic tumor characteristics, such as tumor size, depth of invasion and extension to regional or distant tissues, involvement of regional lymph nodes, and distant metastases. Breast cancer death data during 2000–2014 were based on death certificate information reported to state vital statistics offices and compiled into a national file through the National Vital Statistics System; mortality data in this report cover 100% of the U.S. population. Race and ethnicity were abstracted from medical records for cases and from death certificates for deaths; this report includes all races, white, and black, regardless of ethnicity. Population estimates for the denominators of incidence and death rates were from the U.S. Census, as modified by the National Cancer Institute. Five-year average annual incidence rates for 2009–2013 and death rates for 2010–2014 per 100,000 women were age-adjusted by the direct method to the 2000 U.S. standard population (19 age groups).¶ Average annual percentage change was used to quantify changes in incidence rates during 1999–2013 and death rates during 2000–2014 and was calculated using joinpoint regression, which allowed different slopes for three periods; the year at which slopes changed could vary by race and age.
During 2009–2013, approximately 221,000 breast cancers were diagnosed each year (Table). Overall incidence of breast cancer was similar among black women (121.5 cases per 100,000 population) and white women (123.6 cases per 100,000 population), but differences by age and stage were found. Compared with white women, breast cancer incidence was higher among black women aged <60 years, but lower among black women aged ≥60 years. Black women had a lower percentage of breast cancers diagnosed at a localized stage (54%) than did white women (64%) (Table). Among white women, breast cancer incidence decreased from 1999 to 2004, and then stabilized, decreasing 0.8% per year on average; however, breast cancer incidence was stable from 1999 to 2005 among black women and then nonsignificantly increased (Figure 1). Breast cancer incidence trends differed by race and age, particularly during 1999–2004 when rates decreased only among white women aged ≥50 years. During 1999–2013, among women aged 60–79 years, rates of breast cancer incidence decreased significantly among white women, but increased significantly among black women (https://www.cdc.gov/cancer/breast/statistics/trends_invasive.htm).
Figure 1: Trends* in invasive female breast cancer incidence, by race† and year of diagnosis — United States,§ 1999–2013 (CDC/MMWR, October 14, 2016)
During 2010–2014, approximately 41,000 deaths from breast cancer occurred each year (Table). Breast cancer mortality was 41% higher among black women (29.2 deaths per 100,000 population) than white women (20.6 deaths per 100,000 population). Breast cancer death rates decreased during 2010–2014 among both blacks and whites, although differences in trends by race and age were found (Figure 2). Overall, breast cancer death rates decreased faster among white women (−1.9% per year) compared with black women (−1.5% per year). Among women aged <50 years, breast cancer death rates decreased at the same pace among black and white women, whereas white women aged ≥50 years had significantly larger decreases. The largest difference by race was observed among women aged 60–69 years: breast cancer death rates decreased 2.0% per year among white women compared with 1.0% among black women.
FIGURE 2. Average annual percentage change* in female breast cancer death rates, by age group and race† — United States, 2000–2014 (CDC/MMWR October 14, 2016)
Recent trends in breast cancer incidence suggest that the convergence and now equal incidence for black and white women has been primarily because of incidence increasing among black women, particularly among those aged 60–79 years, and concomitant decreasing or stable rates in white women. Breast cancer mortality is approximately 40% higher among black women compared with white women, with faster decreases in mortality among white women. This report confirms previous findings by race overall (1), and presents age-specific changes for incidence and mortality by race. Continue reading