Sandler, DP; Taylor, JA; Weinberg, CR; Armsby, P; Bilhorn-Janssens, A; Carroll, H; Bittner, D; Jesrani, R; Jones, A; Khodosh, I; Scheier, C; Hodgson, ME; Schwingl, P; Ter Maat, J; Revak, E; Young, T; Yucel, F; Deming-Halverson, SL; Juras, PS; D'Aloisio, AA; Suarez, LM; Kleeberger, CA; Shore, DL; Deroo, LA; ,
BACKGROUND: The Sister Study was designed to address gaps in the study of environment and breast cancer by taking advantage of more frequent breast cancer diagnoses among women with a sister history of breast cancer and the presumed enrichment of shared environmental and genetic exposures.OBJECTIVE: The Sister Study sought a large cohort of women never diagnosed with breast cancer hut who had a sister (full or half) diagnosed with breast cancer.METHODS: A multifaceted national effort employed novel strategies to recruit a diverse cohort, collected biological and environmental samples and extensive data on potential breast cancer risk factors.RESULTS: The Sister Study enrolled 50,884 U.S. and Puerto Rican women 35-74 y of age (median 56 y). Although the majority were non-Hispanic white, well educated, and economically well off, substantial numbers of hiu-der-to-recruit women also enrolled (race/ethnicity other than non-Hispanic white: 16%; no college degree: 35%; household income <$50,000: 26%). Although all had a biologic sister with breast cancer, 16.5% had average or lower risk of breast cancer according to the Breast Cancer Risk Assessment Tool (Gail score). Most were postmenopausal (66%), parous with a first full-term pregnancy <30 y of age (79%), never-smokers (56%) with body mass indexes (BM18) of <29.9 kg/m(2) (70%). Few (5%) reported any cancer prior to enrollment.CONCLUSIONS: The Sister Study is a unique cohort designed to efficiently study environmental and genetic risk factors for breast cancer. Extensive exposure data over the life-course and baseline specimens provide important opportunities for studying breast cancer and other health outcomes in women. Collaborations are welcome. haps://doi.org/10.1289/EHP1923