Convergence of Breast Cancer Incidence but Continued Divergence of Mortality in Black Women and White Women


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Carol E. DeSantis, MPH

Racial Disparities in Breast Cancer

Widening racial disparities in breast cancer mortality are likely to continue, at least in the short term, in view of the increasing trends in breast cancer incidence rates in black women.

—Carol E. DeSantis, MPH, and colleagues

In an article published in CA: A Cancer Journal for Clinicians, Carol E. ­DeSantis, MPH, and colleagues from the American Cancer Society reported that the incidence of breast cancer in black women has caught up to that in white women, whereas the risk of mortality continues to be higher in black women.1

Report Details

Data on incidence trends, probabilities of developing cancer, and cause-specific survival and mortality data were obtained from the Surveillance, Epidemiology, and End Results (SEER) program. Incidence rates by race/ethnicity, stage at diagnosis, and hormone receptor and HER2 status as well as incidence rates by state were obtained using data from the North American Association of Central Cancer Registries. Prevalence data on mammography by race/ethnicity and state were obtained from the 2012 Behavioral Risk Factor Surveillance System.

Incidence

Approximately 231,840 new cases of invasive breast cancer and 40,290 breast cancer deaths are expected to occur among U.S. women in 2015, along with 60,290 new diagnoses of in situ breast cancer. From 2008 to 2012, breast cancer incidence rates increased by 0.4% per year in black women and by 1.5% per year in Asian/Pacific Islander women but did not change significantly in white, Hispanic, or American Indian/Alaska Native women. In 2012, rates in blacks and whites were virtually identical.

During this period, incidence rates were significantly higher in black women vs white women in seven states (Alabama, Kentucky, Louisiana, Mississippi, Missouri, Oklahoma, and Tennessee), primarily located in the South. For the 5-year period, the incidence per 100,000 population was 128.1 in white women, 124.3 in black women, 91.9 in American Indian/Alaska Native women, 91.9 in Hispanic women, and 88.3 in Asian/Pacific Islander women.

The authors noted that the increase in incidence in black women has been driven by an increase in estrogen receptor–positive breast cancers and that this trend may reflect the increasing rate of obesity in black women—from 39% in 1999 through 2002 to 58% in 2009 through 2012. High recent body mass index has been associated with significantly increased risk of estrogen receptor–positive breast cancer in black women.

Stage at Diagnosis

Stage distribution data for 2012 show that whites and Asians/Pacific Islanders had the highest proportions of localized breast cancers (64% and 63%, respectively) and the smallest proportions of regional (28% and 30%) and distant (5% and 5%) disease. Black women had the smallest proportion of localized breast cancers (53%) and the highest proportions of regional (35%) and distant (8%) disease. For localized, regional, and distant disease, respectively, proportions were 56%, 34%, and 6% among Hispanic women and 57%, 32%, and 6% among American Indians/Alaska Natives.

Receptor Status

In 2012, black women had the highest proportion of triple-negative cases and the lowest proportion of hormone receptor–positive/HER2-negative cases. Proportions of cases that were hormone receptor–positive/HER2-negative, hormone receptor–positive/HER2-positive, triple-negative, and hormone receptor–negative/HER2-positive were 76%, 10%, 11%, and 4% in white women, 62%, 11%, 22%, and 5% in black women, 71%, 12%, 12%, and 5% in Hispanic women, and 72%, 11%, 10%, and 7% in Asian/Pacific Islander women.

Mortality

From 1989 to 2012, breast cancer death rates decreased by 36%, with this decrease being evident in all racial/ethnic groups except American Indians/Alaska Natives. From 2003 through 2012, breast cancer mortality declined annually by 1.8% in whites, 1.5% in Hispanics, 1.4% in blacks, and 1.0% in Asians/Pacific Islanders but remained unchanged among American Indians/Alaska Natives.

A divergence in mortality between black and white women emerged in the early 1980s and has since continued to widen, such that the mortality rate was 42% higher in black women in 2012. For 2008 to 2012, mortality per 100,000 was 21.9 in whites, 31.0 in blacks, 15.0 in American Indians/Alaska Natives, 14.5 in Hispanics, and 11.4 in Asians/Pacific Islanders.

The authors noted that the mortality difference between black women and white women likely reflects a combination of factors, including differences in incidence rates, stage at diagnosis, tumor characteristics, obesity, and comorbidities, as well as differences in access, adherence, and response to appropriate treatments, differences in quality of mammography screening, and delayed follow-up for abnormal mammography findings.

In 2012, proportions of women aged ≥ 45 years with mammography within the past 2 years ranged by state from 66% to 86% among white women and from 68% to 89% among black women (in 34 states with sufficient sample sizes to permit estimates).

The authors concluded: “Widening racial disparities in breast cancer mortality are likely to continue, at least in the short term, in view of the increasing trends in breast cancer incidence rates in black women.” ■

Disclosure: The authors reported no potential conflicts of interest.

Reference

1. DeSantis CE, Fedewa SA, Goding Sauer A, et al: Breast cancer statistics, 2015: Convergence of incidence rates between black and white women. CA Cancer J Clin. October 29, 2015 (early release online).

 

 


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