Abstract A17: In utero DDT exposure and breast density in early menopause by maternal history of breast cancer

Studies examining intrauterine environmental exposures and breast cancer risk are challenged by the long induction period between exposure and breast cancer development. One strategy to address this challenge is to examine the relationship between exposures and intermediate markers of breast cancer risk. Mammographic breast density (MBD) is considered an intermediate marker for breast cancer—having mostly dense breasts is associated with nearly a 4-fold increase in breast cancer as compared with having mostly fatty breasts. Here we examined the relation between intrauterine dichlorodiphenyltrichloroethane (DDT) exposure (o,p’-DDT, p,p’-DDT, and p,p’-DDE) to MBD in midlife. We focused our analyses on o,p’-DDT exposure when mutually adjusted for p,p’-DDE given our previous report of a positive association between intrauterine o,p’-DDT exposure and daughters’ breast cancer (BC) risk. We estimated associations of early postpartum serum DDTs with MBD in 224 daughters of women in the Child Health and Development Studies pregnancy cohort whose mothers did not develop BC (MBCa-negative) and 156 daughters whose mothers did develop BC (MBCa-positive). In MBCa-positive daughters, highest relative to lowest quartile of o,p’-DDT exposure was associated with a 17-unit higher dense area (95% CI= 2.6-31.2; Ptrend=0.01); associations persisted after adjusting for p,p’-DDT. MBD, an important intermediate marker of BC risk, may be affected by intrauterine DDT exposures; MBCa status may modify the association. Citation Format: Jasmine A. McDonald, Piera M. Cirillo, Parisa Tehranifar, Nickilou Y. Krigbaum, Natalie Engman, Barbara A. Cohn, Mary Beth Terry. In utero DDT exposure and breast density in early menopause by maternal history of breast cancer [abstract]. In: Proceedings of the AACR Special Conference on Environmental Carcinogenesis: Potential Pathway to Cancer Prevention; 2019 Jun 22-24; Charlotte, NC. Philadelphia (PA): AACR; Can Prev Res 2020;13(7 Suppl): Abstract nr A17.