Data Availability Statement The R code and aggregate penetrance estimates used to generate the results of this study are openly available at https://github.com/janewliang/AggreMendMod. Supporting Information References , , , et al. 2003. “The Cancer Genetics Network: Recruitment Results and Pilot Studies.” Public Health Genomics 6, no. 3: 171–177. , , , et al. 2002. “A Comprehensive Model for Familial Breast Cancer Incorporating BRCA1, BRCA2 and Other Genes.” British Journal of Cancer 86, no. 1: 76.