This Komen-funded study has recruited women with young-onset breast cancer and, when available, their parents. We will combine their data with the DNA and environmental data now being collected from their unaffected sisters (who previously joined the Sister Study) and saliva-based DNA collected from their parents. We will use a nuclear-family-based approach to study genetic and environmental factors involved in young-onset breast cancer. The study gains enormous operational efficiency advantages, by taking advantage of the infrastructure that is already in place and functioning smoothly for the Sister Study (Dale Sandler, PI). We are almost done with collecting clinical data and validating the diagnoses for all these young-onset cases. Follow-up of these cases (through the Sister Study) will also allow us to identify environmental, clinical, and genetic factors that influence health after treatment. Case-parent analyses of gene variants are protected against bias due to confounding by genetic heritage, and also permit detection of both maternally-mediated genetic effects and parent-of-origin (imprinting) effects. In the proposed study, the participating affected sisters are each completing a computer-assisted telephone interview like the one their sister completed for the Sister Study, providing information about personal exposures, reproductive history, and past occupational exposures. Environmental effects will be identifiable through a paired comparison of affected and unaffected sisters. Gene-by-exposure interactions will be assessed with novel statistical methods. In summary, the proposed study leverages off the ongoing Sister Study to build a cost-effective, powerful, and statistically independent study of young-onset breast cancer. Findings related to combined effects of genetic variants and environmental factors can be replicated later in the Sister Study. We have completed study enrollment. With augmentation by including some newly diagnosed young-onset cases from the Sister Study we have enrolled nearly 1500 cases providing both questionnaire data and DNA. We have also enrolled 1403 of their parents, who provided DNA. This work was accomplished with assistance from the EB support services contract. We recently secured permission from the funding agency (Susan G. Komen for the Cure) for a no-cost extension and for redirecting the money originally intended for a candidate gene approach to instead carry out a GWAS, using the Illumina OmniExpress plus Exome chip. Carried out through a contract with the Center for Inherited Disease Research, this genotyping project should deliver more than a million SNPs on these families. The final DNA extractions are now being done and the genotyping will be accomplished in the next few months. We hope to use these data to find gene-by-environment causal factors for young onset breast cancer. By combining the Two Sister cases with those arising in the Sister Study we will also be able to study complexes of factors that are related to healthy recurrence-free survival following treatment. Together with a postdoc, Chunyuan Fei, we published two papers this year based on the Two Sister Study. In the first, we looked at history of exposure to ovulation-stimulating fertility drugs. These exposures have hormonal effects that have raised concerns about breast cancer, but literature has been mixed. We recognized that the exposures are different if a pregnancy occurs, because the levels of hormones remain elevated for the first trimester of pregnancy, potentially influencing the remodeling of breast tissue. Based on a conditional logistic regression model exposed women had reduced risk compared to the unexposed, but that apparent protection was lost if the treatment led to a pregnancy. We have another paper in press related to the apparent protection enjoyed by women who have a history of menopause-associated symptoms. We have several papers related to the Sister Study. One, which has been provisionally accepted at the Journal of the National Cancer Institute evaluated methylation at about 27,000 CpG sites in the genome using blood that had been collected at baseline and related those results to the later development of breast cancer. Methylation status was predictive of risk of cancer.