Abstract P3-04-03: Per- and Polyfluoroalkyl Substances (PFAS) in Drinking Water and Breast Cancer Risk among Women in the Military

Abstract For several decades, breast cancer rates have increased among younger women under age 50. Previous studies indicated women serving in the U.S. Military had higher incidence of early onset breast cancer than expected based on the U.S. population, but the reasons remain unclear. High levels of Per- and Polyfluoroalkyl Substances (PFAS) ), known endocrine disrupting chemicals, have been found in drinking water on a number of US military bases. PFAS are in many industrial and consumer products, but the use of Aqueous Film Forming Foam (AFFF) for firefighting since the 1970’s is considered the major source of contamination on military installations. We assessed the association of duration assigned to a military installation reported to have high drinking water PFAS levels with breast cancer rates using data from a nested case-control study among active duty women in the military. Through the Department of Defense (DoD) Cancer Registry, we identified 832 women diagnosed with (711) invasive breast cancer (BC) or with (121) ductal carcinoma in situ (DCIS), who joined the military since 1990 and were diagnosed between January 1, 2000 and December 31, 2022, while on active duty. We selected 856 matched controls from active duty women who had no reported breast cancer diagnosis at the time of the cases’ diagnosis, joined the military in the same year, were born in the same year, and of the same race/ethnicity. In this unique study sample 85% of cases are under the age of 45 and 56% are non-White. In a 2020 report to Congress, the DoD identified 22 military installations where the drinking water PFAS levels were above the 2016 EPA guidelines of 70 ppt. Among the women in this study, 46.8% of the cases and 43.7% of the controls were assigned to one of these 22 installations at some time prior to the cases’ year of diagnosis. To estimate the rate ratio for breast cancer associated with time assigned to the identified installations, we calculated the odds ratio (OR) with 95% confidence intervals (CI) using a logistic regression model that controlled for the matching factors. Compared to women never assigned to any of the identified 22 installations, those assigned for three or more years had an OR = 1.45 (95% CI: 1.09-1.96) for invasive BC or DCIS. The increase in the rate was slightly higher for invasive BC only (OR = 1.52; 95% CI: 1.11-2.07), for those diagnosed with invasive BC before the age of 45 (OR= 1.79; 95% CI:1.27-2.53), and for those diagnosed with invasive BC before 2016, when PFAS contamination was likely higher (OR = 2.02; 95% CI: 1.27-3,21). While assignment to a base with high levels of PFAS in drinking water does not necessarily determine individual exposure levels, these findings might in part provide an explanation for the previously reported higher rates of breast cancer among women serving in the U.S. Military. Disclaimer: The views expressed are those of the authors and do not necessarily reflect the official views of the Uniformed Services University of the Health Sciences or the Department of Defense. Citation Format: Celia Byrne, Michelle S. Mellers, Lynsey L. Lewis, Barbara J. Fuhrman. Per- and Polyfluoroalkyl Substances (PFAS) in Drinking Water and Breast Cancer Risk among Women in the Military [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P3-04-03.