Abstract P4-03-03: Elevated Risk of Breast Cancer Diagnosis in Women with Dense Breasts reflects a similarly Elevated Risk of Breast Cancer Onset that is Robust to the Effect of Density on Mammography Sensitivity

Abstract

Abstract Dense breasts are associated with a higher risk of breast cancer diagnosis, which has impacted risk prediction tools and patient notification policies. However, given that mammography is less sensitive for women with dense breasts and these women may be subject to different confirmation testing pathways, the true association between breast density and cancer risk is unknown. We investigated the relationship between breast density and onset using a natural history model that accounts for differential sensitivity and rates of exams by breast density. Data consisted of Breast Cancer Surveillance Consortium mammogram and cancer outcomes among women aged 40-54 with a first digital mammogram between 2000-2018 (N=33,542). Of these, 15,092 had non-dense (almost entirely fatty or scattered fibroglandular densities) and18,450 had dense (heterogeneously dense or extremely dense) breasts. We estimated the empirical sensitivity of mammograms in dense and non-dense breasts (fraction of diagnosed cancers that were screen detected) and examined rates of mammograms by density. We estimated the relative risk of breast cancer diagnosis five years after the first exam using Kaplan Meier methods and the relative risk of breast cancer onset from a natural history model, assuming density-specific sensitivity was equal to the empirical sensitivity. Empirical sensitivity was .88 in women with non-dense and .78 in women with dense breasts. Mammogram utilization was somewhat higher in women with dense breasts (HR for subsequent mammograms 1.10 (95% CI [1.07, 1.12]). The relative risk of diagnosis for dense versus non-dense breasts was 1.80 (95% CI [1.46,2.57]); based on the natural history model the relative risk of onset was 1.73 [1.43,2.25]. The estimated relative risk of onset ranged from 1.67 to 2.03 under assumptions that the relative sensitivity of the screening episode for dense versus non-dense breasts was 1.0 to 0.4. In conclusion, the association of risk of breast cancer onset with breast density is robust to assumptions about the relative sensitivity in dense and non-dense breasts. Citation Format: Jane M. Lange, Charlotte Gard, Ellen O’meara, Ruth Etzioni. Elevated Risk of Breast Cancer Diagnosis in Women with Dense Breasts reflects a similarly Elevated Risk of Breast Cancer Onset that is Robust to the Effect of Density on Mammography Sensitivity [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-03-03.