Background: Psychosocial trauma has been hypothesized to influence breast cancer risk, but little is known about how co-occurring traumas—particularly during early life—may impact incidence. We examine the relationship between multiple measures of early-life trauma and incident breast cancer. Methods: The Sister Study is a prospective cohort study of U.S. women (N=50,884; enrollment 2003-2009; ages 35-74). Of 45,961 eligible participants, 3,070 developed invasive breast cancer or ductal carcinoma in situ through 2017. We assessed trauma before age 18 using previously studied measures (cumulative score, individual trauma type, and substantive domain) and a six-class latent variable to evaluate co-occurring traumas. We accounted for missing data using multiple imputation and estimated hazard ratios (HR) and 95% confidence intervals (CI) using Cox proportional hazards models. Results: Approximately 49% of participants reported early-life trauma. Using the latent class variable approach, breast cancer hazard was higher among participants who had sexual trauma or household dysfunction (HR=1.1; CI:0.93, 1.3), or moderate (HR=1.2; CI:0.99, 1.4) but not high trauma (HR=0.66; CI:0.44, 0.99) compared to low trauma. Breast cancer HRs associated with sexual early-life trauma or household dysfunction were elevated for pre- and post-menopausal breast cancer and by estrogen receptor status. We found no effect modification by race–ethnicity. Estimated effects were attenuated with report of constant childhood social support. Conclusions: Breast cancer incidence varied by latent patterns of co-occurring early-life trauma. Models capturing childhood social support and trauma patterning, rather than cumulative or discrete indicators, may be more meaningful in breast cancer risk assessment. Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.
