The Sister Study Cohort: Baseline Methods and Participant Characteristics

Abstract

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 but who had a sister (full or half) diagnosed with breast cancer.Methods:A multifaceted national effort employed novel strategies to recruit a diverse cohort, and 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 35–74y of age (median 56 y). Although the majority were non-Hispanic white, well educated, and economically well off, substantial numbers of harder-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 <30y of age (79%), never-smokers (56%) with body mass indexes (BMIs) of <29.9 kg/m2 (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. https://doi.org/10.1289/EHP1923

Association between meat consumption and risk of breast cancer: Findings from the Sister Study

“…Strengths of the present study include large sample size, comprehensive baseline risk factor assessment and ability to account for time‐varying menopausal status and to explore impact of family history and other behavioral and lifestyle factors. The Sister Study also is prospective in design with high retention rates among participants . Potential limitations include the use of a single FFQ administered at baseline.…”

“…A total of 50,884 women completed the extensive baseline enrollment process, which consisted of a comprehensive interview and self‐completed questionnaires covering medical and family cancer history as well as lifestyle and demographic characteristics, including diet and a home exam during which height, weight and weight and hip circumference were measured. Details of the study design, data collection and outcome measurements are described elsewhere . The Sister Study was approved by National Institute of Environmental Health Services/NIH and Copernicus Group Institutional Review Boards, and all participants provided written informed consent.…”

Higher diet‐dependent acid load is associated with risk of breast cancer: Findings from the sister study

“…Study participants came from the Sister Study, a nationwide prospective cohort study designed to investigate environmental and genetic risk factors for breast cancer . During 2003 to 2009, 50,884 US and Puerto Rican women whose sister had been diagnosed with breast cancer were enrolled.…”

“…Study participants are asked to report breast cancer diagnosis annually and complete detailed follow‐up questionnaires every 2–3 years to provide information on risk factors and changes in health status. Response rates have been over 90% throughout follow‐up The data presented in the current analyses were obtained from Sister Study data release 5.0 (July 2016), which included incident breast cancer cases diagnosed as of August 14, 2015.…”

“…Agreement was high between self‐reported breast cancer diagnosis and medical records (99.4%). Classification of an invasive cancer (99.3%), and estrogen receptor (ER) positive status (99.3%) were also in high agreement . Therefore, self‐reported cases and tumor characteristics were included in the analyses when medical records were not available.…”