The impact of the rise in breast cancer incidence associated with mammography diffusion on the prevalence of breast cancer family history is unknown, and may attenuate risk associations between family history and breast cancer. Methods: The proportions of women 40–74 years reporting a first-degree family history of breast cancer were estimated in the Breast Cancer Surveillance Consortium (BCSC, N = 1,170,900) from 1996–2012 and Collaborative Breast Cancer Study (CBCS; cases N = 23,400; controls N = 25,460) from 1987–2007. Breast cancer (ductal carcinoma in situ and invasive) relative risk estimates associated with family history and 95% confidence intervals (CI) were calculated using multivariable Cox proportional hazard (BCSC) and logistic regression (CBCS) models. Results: The proportion of women reporting a family history increased from 11% in the 1980s to 16% in 2010–13. Family history was associated with a 60% increased risk of breast cancer in the BCSC (hazard ratio = 1.61, 95% CI = 1.55–1.66) and CBCS (odds ratio = 1.66, 95% CI = 1.58–1.74), with relative risks decreasing with age. Trends in relative risks were not evident over time or stage of disease at diagnosis, except among older women (60–74) where estimates were attenuated in more recent years (P-trend = 0.08 for both cohorts). Conclusion: The proportion of women with a first-degree family history of breast cancer increased over time and by age, nonetheless breast cancer risk associations with family history were constant over time for women 40–59. First-degree family history of breast cancer remains an important breast cancer risk factor, especially for younger women, despite its increasing prevalence in the mammography screening era

The following are the 16 highest scoring abstracts of those submitted for presentation at the 41st Annual ASPO meeting held March 12–14, 2017, in Seattle, WA.