Abstract
PurposeThe etiology of young-onset breast cancer (BC) is poorly understood, despite its greater likelihood of being hormone receptor-negative with a worse prognosis and persistent racial and socioeconomic inequities. We conducted a population-based case–control study of BC among young Black and White women and here discuss the theory that informed our study, exposures collected, study methods, and operational results.MethodsCases were non-Hispanic Black (NHB) and White (NHW) women age 20–49 years with invasive BC in metropolitan Detroit and Los Angeles County SEER registries 2010–2015. Controls were identified through area-based sampling from the U.S. census and frequency matched to cases on study site, race, and age. An eco-social theory of health informed life-course exposures collected from in-person interviews, including socioeconomic, reproductive, and energy balance factors. Measured anthropometry, blood (or saliva), and among cases SEER tumor characteristics and tumor tissue (from a subset of cases) were also collected.ResultsOf 5,309 identified potentially eligible cases, 2,720 sampled participants were screened and 1,812 completed interviews (682 NHB, 1140 NHW; response rate (RR): 60%). Of 24,612 sampled control households 18,612 were rostered, 2,716 participants were sampled and screened, and 1,381 completed interviews (665 NHB, 716 NHW; RR: 53%). Ninety-nine% of participants completed the main interview, 82% provided blood or saliva (75% blood only), and SEER tumor characteristics (including ER, PR and HER2 status) were obtained from 96% of cases.ConclusionsResults from the successfully established YWHHS should expand our understanding of young-onset BC etiology overall and by tumor type and identify sources of racial and socioeconomic inequities in BC.
Highlights
In the United States (US), nearly one quarter of annual breast cancer (BC) cases occur in women under 50 years of age and the incidence is increasing [1, 2]
This study protocol was approved by the Institutional Review Boards at the University of Wisconsin—Milwaukee (UWM); Michigan State University (MSU); Wayne State University (WSU); the Michigan Department of Community Health; University of Southern California (USC); the California Committee for the Protection of Human Subjects (CPHS); and for the Medical College of Wisconsin (MCW), IRB oversight was deferred to UWM
1,381 a Excludes non-Hispanic Black (NHB) and Non-Hispanic White (NHW) cases < 45 years of age identified by the SEER Registry post the study recruitment period (n = 146; DT: n = 74; LA: n = 72) b Sampled/potentially eligible cases who did not complete a telephone screener and were determined to be ineligible based on SEER information c Active physician approval required by specific hospitals among a subset of case participants in Detroit d For efficiency, 60% of households identified by the Westat address list vendor as likely to include at least one “Hispanic” adult were randomly excluded
Summary
In the United States (US), nearly one quarter of annual breast cancer (BC) cases occur in women under 50 years of age and the incidence is increasing [1, 2]. Overall BC mortality was 40% higher in NHB compared to NHW women during 2013–2017 [17] and this inequity is pronounced among women < 50 years of age, where mortality was 82% higher in NHB compared to NHW women in 2018 [19]. Few modifiable factors have been identified to inform BC prevention strategies [26], in young women [9, 27,28,29,30,31] and by tumor type [9, 13], or to explain racial and socioeconomic inequities in BC incidence [32,33,34]. We document details of the YWHHS study design, life-course measures collected, data collection methods, response and cooperation rates, and provide a description of our final study population
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