Journal of the National Cancer Institute Advance Access published online on July 7, 2009
JNCI Journal of the National Cancer Institute, doi:10.1093/jnci/djp176
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Published by Oxford University Press 2009.
ARTICLE |
Underlying Causes of the Black–White Racial Disparity in Breast Cancer Mortality: A Population-Based Analysis
Affiliations of authors: Biostatistics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Rockville, MD (IM, WFA, PSR); Breast Care Center, National Naval Medical Center, Uniformed Services University, Bethesda, MD (IJ)
Correspondence to: Idan Menashe, Biostatistics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, 6120 Executive Blvd, Executive Plaza South, Rm 8047, Rockville, MD 20852-7244 (e-mail: menashei{at}mail.nih.gov).
Background: In the United States, a black-to-white disparity in age-standardized breast cancer mortality rates emerged in the 1980s and has widened since then.
Methods: To further explore this racial disparity, black-to-white rate ratios (RRsBW) for mortality, incidence, hazard of breast cancer death, and incidence-based mortality (IBM) were investigated using data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results program on 244 786 women who were diagnosed with breast cancer from January 1990 through December 2003 and followed through December 2004. A counterfactual approach was used to examine the expected IBM RRsBW, assuming equal distributions for estrogen receptor (ER) expression, and/or equal hazard rates of breast cancer death, among black and white women.
Results: From 1990 through 2004, mortality RRBW was greater than 1.0 and widened over time (age-standardized breast cancer mortality rates fell from 36 to 29 per 100 000 for blacks and from 30 to 22 per 100 000 for whites). In contrast, incidence RRBW was generally less than 1.0. Absolute hazard rates of breast cancer death declined substantially for ER-positive tumors and modestly for ER-negative tumors but were persistently higher for blacks than whites. Equalizing the distributions of ER expression in blacks and whites decreased the IBM RRBW slightly. Interestingly, the black-to-white disparity in IBM RRBW was essentially eliminated when hazard rates of breast cancer death were matched within each ER category.
Conclusions: The black-to-white disparity in age-standardized breast cancer mortality was largely driven by the higher hazard rates of breast cancer death among black women, diagnosed with the disease, irrespective of ER expression, and especially in the first few years following diagnosis. Greater emphasis should be placed on identifying the etiology of these excess hazards and developing therapeutic strategies to address them.
| CONTEXT AND CAVEATS Prior knowledge Since the 1980s, a widening disparity in age-adjusted mortality rates for black and white women diagnosed with breast cancer has emerged. Study design Based on data from the National Cancer Institute's Surveillance, Epidemiology, and End Results program, the authors calculated temporal trends in black-to-white ratios of mortality, incidence, hazard for death from breast cancer, and incidence-based mortality (IBM), with some analyses stratified by estrogen receptor (ER) status and age. Contribution The work indicates that the black-to-white disparity in breast cancer mortality is largely due to a higher hazard of death in black women diagnosed with the disease irrespective of ER status. Implications Research into the reasons for relatively poor outcomes for black women with breast cancer is warranted. Limitations IBM analyses only captured the experience of women with breast cancer in the first five years following diagnosis. From the Editors
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Manuscript received October 27, 2008; revised April 16, 2009; accepted May 20, 2009.
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J Natl Cancer Inst 2009 101: 969.
J Natl Cancer Inst 2009 101: 969.
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