Journal of the National Cancer Institute Advance Access published online on May 13, 2008
JNCI Journal of the National Cancer Institute, doi:10.1093/jnci/djn112
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Published by Oxford University Press 2008.
CORRESPONDENCE |
Racial Differences in Breast Cancer Trends in the United States (2000–2004)
Affiliations of authors: Biostatistics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD (RMP, RKM, WFA); Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT
Correspondence to: Ruth M. Pfeiffer, PhD, Biostatistics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD (e-mail: pfeiffer{at}mail.nih.gov).
A decrease in US breast cancer incidence of at least 6.7% from 2002 to 2003 has been reported (1) and attributed to a reduction in hormone replacement therapy (HRT), following the Women's Health Initiative (WHI) report in July 2002. Two recent studies (2,3) described changes in breast cancer incidence for different racial and ethnic groups using data from the Surveillance, Epidemiology, and End Results (SEER) 13-Registry Database. We provide complementary data that add incidence changes by age, estrogen receptor (ER) expression, and race.
The SEER 17-Registry Database recorded 101 118 and 97 512 women 20 years and older who were newly diagnosed with invasive female breast cancer during 2000–2001 (before the WHI report) and 2003–2004 (after the WHI report), respectively. Among non-Hispanic whites (Figure 1, A), age-specific incidence rates confirmed marked declines in breast cancer incidence for women over 50 years of age. However, among black women aged 50–69 years (the age group in which HRT use is most common, Figure 1, B), incidence rates were slightly higher in 2003–2004 than in 2000–2001: for blacks aged 50–69 years, age-standardized (2000 US population) rates increased 1.8% (95% confidence interval [CI] = 1.7% to 1.9%), from 277.3 to 282.3 per 100 000 person-years; for blacks aged 70 years and older, standardized rates dropped only 3.7% (95% CI = –4.0% to –3.5%). Among Hispanic whites and Asian or Pacific Islanders (Figure 1, C and D), age-specific rates for those over 50 years of age declined modestly from 2001–2002 to 2003–2004.
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To further investigate trends among non-Hispanic white and black women aged 50–69 years, we stratified incidence rates by ER expression of the tumors, allocating tumors with unknown ER status to ER-positive or ER-negative categories in proportion to the observed race- and age-specific numbers of ER-positive or ER-negative tumors. For non-Hispanic white women aged 50–69 years, incidence of ER-positive breast cancers dropped 14.4% from 2000–2001 to 2003–2004 whereas ER-negative tumors declined only 4.7%. For black women aged 50–69 years, ER-positive breast cancer incidence showed no change from 2000–2001 to 2003–2004 whereas incidence of ER-negative tumors increased 4.0%.
Changes in mammography screening cannot explain incidence changes among black women because screening prevalence remained constant for blacks during 2000–2004 (4). We sought to explain why decreases in HRT usage in black women (5) did not lower ER-positive rates among blacks aged 50–69 years. Although percent changes in HRT usage before and after WHI were similar among racial groups (5), overall HRT usage was reportedly lower among blacks than among non-Hispanic whites, Hispanics, or Asian or Pacific Islanders (5). Additionally, because blacks have high hysterectomy rates, estrogen alone may be more commonly prescribed than combination therapy (estrogen plus progestin), conferring a lower breast cancer risk (6). For these reasons, a proportional decrease in HRT use may have affected a smaller proportion of black women compared to non-Hispanic whites. Finally, whereas the prevalence of obesity dropped 13.2% among non-Hispanic white women 60 years and older from 1999–2000 to 2003–2004, it increased by 7.6% among black women 60 years and older (7), possibly offsetting HRT-related breast cancer declines in black women.
These analyses shed additional light on race-specific changes in breast cancer incidence, particularly for women aged 50–69 years, the age group most affected by changes in HRT use. In this age group, invasive breast cancer incidence dropped from 2000–2001 to 2003–2004 for non-Hispanic whites, Hispanic whites, and Asian or Pacific Islanders but increased 1.8% for blacks. These differences in total invasive breast cancer incidence reflected corresponding differences in both ER-positive (14.4% decrease in whites vs 0% change in blacks) and ER-negative (4.7% drop in whites vs 4.0% increase in blacks) invasive breast cancer incidence.
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