Acknowledgments BCAC was funded by Cancer Research UK (C1287/A16563) and by the European Community’s Seventh Framework Programme under grant agreement no. 223175 (HEALTH-F2-2009-223175) (COGS) and by the European Union’s Horizon 2020 Research and Innovation Programme under grant agreements 633784 (B-CAST) and 634935 (BRIDGES). Genotyping of the OncoArray was principally funded by Government of Canada through Genome Canada and the Canadian Institutes of Health Research (grant GPH-129344), the Ministère de l’Économie, de la Science et de l’Innovation du Québec through Genome Québec, the Quebec Breast Cancer Foundation; NIH grants U19 CA148065 and X01HG007492; and Cancer Research UK (C1287/A10118 and C1287/A16563). Genotyping of the iCOGS array was funded by the European Union (HEALTH-F2-2009-223175), Cancer Research UK (C1287/A10710), the Canadian Institutes of Health Research for the “CIHR Team in Familial Risks of Breast Cancer” program, and the Ministry of Economic Development, Innovation and Export Trade of Quebec (grant # PSR-SIIRI-701). Combining the GWAS data was supported in part by the National Institutes of Health (NIH) Cancer Post-Cancer GWAS initiative grant: No. 1 U19 CA 148065 (DRIVE, part of the GAME-ON initiative). We thank all the individuals who took part in these studies and all researchers, clinicians, technicians, and administrative staff who enabled this work to be carried out. For other acknowledgments and sources of funding, see Supplemental Acknowledgments.