摘要：Objectives. We investigated whether there were socioeconomic and racial/ethnic disparities in recent reported declines in overall US breast cancer incidence rates attributed to post-2002 declines in hormone therapy use following publication of the Women's Health Initiative study. Methods. We analyzed 1992–2005 US breast cancer incidence data from the US Surveillance, Epidemiology and End Result (SEER) 13 Registries Database, stratified by race/ethnicity, county income level, age, and estrogen receptor (ER) status. Results. As we hypothesized, between 1992 and 2005, the temporal pattern of rising and then falling US breast cancer incidence rates occurred only among White non-Hispanic women who lived in high-income counties, were aged 50 years and older, and had ER-positive tumors. No such trends were evident—regardless of county income level, ER status, or age—among Black non-Hispanic, Asian/Pacific Islander, Hispanic, or—where numbers were sufficient to conduct meaningful analyses—American Indian/Alaska Native women. Conclusions. The recent decline in US breast cancer incidence was not equally beneficial to all women, but instead mirrored the social patterning of hormone therapy use. Joint information on socioeconomic resources and race/ethnicity is vital for correctly understanding disease distribution, including that of breast cancer. Since 2006, 14 population-based studies—8 American, 1 – 8 5 European, 9 – 13 and 1 Australian 14 —have documented unanticipated annual declines in breast cancer incidence of around 10%, especially among women aged 50 years and older with estrogen receptor (ER)-positive tumors. All of these investigations have attributed these declines to the dramatic reduction in use of hormone therapy 15 – 18 following the publication, in July 2002, of the results of the Women's Health Initiative (WHI) study. 19 Like the 1998 Heart and Estrogen/Progestin Replacement Study (HERS) 20 and its 2002 follow-up, 21 the WHI found that, contrary to expectations, hormone therapy did not decrease—and may in fact have increased—risk of cardiovascular disease, and it also confirmed that long-term use of combined estrogen plus progestin increased risk of breast cancer. To date, however, scant research has examined whether recent reported declines in breast cancer incidence varied not only by age and ER status but also—like hormone therapy use 16 , 18 , 20 – 26 —by race/ethnicity (examined in only 3 US studies 4 – 6 ) and socioeconomic position (not examined in any studies, in the United States or any other country). Within the United States, data indicate that, until 2002, use of hormone therapy was most common among more affluent, healthier, and predominantly White women (i.e., women with access to medical care, who could afford hormone therapy and who did not have contraindications against its use). 16 , 18 , 20 – 24 Socioeconomic gradients in hormone therapy use have also been reported in 2 countries with national health systems—Britain 25 and Sweden 26 —suggesting that access to medical care alone is not the full reason for the higher use by more affluent women. We accordingly designed our study to test the hypothesis that the recent reported declines in US breast cancer incidence varied not only by age and ER status but also by race/ethnicity and socioeconomic position. Our study base consisted of county-level incidence data from the US Surveillance, Epidemiology and End Result (SEER) 13 Registries Database, 27 which in 2000 covered 14% of the total US population. 28 The time period spanned the years 1992 to 2005, thereby encompassing the initial recommendations by the Food and Drug Administration and American College of Physicians (in 1991 and 1992, respectively) for use of hormone therapy to prevent cardiovascular disease 17 as well as the 1998 HERS 20 and 2002 WHI study results 19 and HERS follow-up results. 21 Our prediction was that the sharpest post-WHI declines in breast cancer incidence would occur among White non-Hispanic women living in high-income counties, especially those aged 50 to 69 years who had ER-positive tumors.
