Genetics of Mammographic Appearances and Patterns (The GenMap Study)

High mammographic density (HMD) is the strongest risk factor for non-familial breast cancer apart from age and gender. Studies of sisters and twins suggest that approximately 67% of the variation in density is attributable to common genetic factors. However, to date, efforts to identify genetic determinants of HMD have achieved limited success. We and others (Boyd et al Lancet Oncol 2009) postulate that this lack of progress in identifying genetic determinants of density is related to a failure to study younger women and misclassification of density. As women age, their breast tissues undergo atrophy, which is manifested radiologically as a decrease in mammographic density, resulting in a convergence of density values and a masking of inter-person variation. This protocol is intended to demonstrate the feasibility of methods that we plan to use in a full-scale analysis of mammographic density among women under age 50 years who receive care at the University of Vermont, Fletcher Allen Health Care (FAHC) and have been followed through the Vermont Breast Cancer Surveillance System (VBCSS).

The Hormonal and Reproductive Epidemiology Branch (HREB) is currently conducting a cross-sectional study entitled, Breast Radiology Evaluation and Study of Tissues (BREAST) Stamp Project which aims to understand why mammographically dense tissues are related to elevated breast cancer risk. This project is being conducted within the VBCSS using breast cancer awareness Stamp Act funds. The BREAST Stamp project has focused on women between the ages of 40-65 years who were referred for radiologically-guided biopsy to evaluate an abnormality identified on a screening mammogram. The study has successfully enrolled over 400 women with collection of questionnaires, buccal and blood samples, and tissues. The study will continue recruiting through May 2010, with a targeted enrollment of 450-500 women. Through the infrastructure developed for the BREAST Stamp Project, mammographic volumetric density data, assessed using a novel method with density phantoms developed at UCSF, has been collected on approximately 25,000 screened women of all ages from February 2008-present.

The current protocol describes a study in which we propose to capitalize on infrastructure that has been established through the BREAST Stamp Project. We propose to perform this study in two phases: Phase one will be a feasibility study: specifically, we propose to demonstrate that we can use a mailing to collect Oragene tube format saliva collection kits as a source of germline DNA and a short self-administered questionnaire. This collection of specimens and data will be used to inform the launch of phase two, the full-scale study to identify determinants of mammographic volumetric density among approximately 10,000 women less than 50 years of age for whom raw images and density data are already collected. During the first phase we hope to demonstrate feasibility by achieving at least 60% participation with unbiased representation of subjects with regard to demographics and volumetric density measurements. Once feasibility of this approach is established, we propose to launch the full-scale study by contacting the remaining (approximately 10,000) women with existing volumetric density data to collect questionnaires and DNA samples necessary to delineate the genetic determinants of mammographic density, as well as to investigate hypothesized risk factors for mammographic density and breast cancer risk, such as alcohol intake, cigarette smoking, and breastfeeding history.