Understanding Breast Cancer Risk and Screening in Transgender Persons through a Pilot Breast Cancer Screening Program - PROJECT SUMMARY/ABSTRACT In the U.S., an estimated 1.4 million people identify as transgender (TG), defined as a person whose gender is different than their sex assigned at birth, and are a designated minority population by the NIH (NOT-MD-19-001). Many TG persons take gender-affirming hormone therapy, usually estrogen or testosterone based, to alter their physical appearance and improve their psychological health. Lifetime exposure to estrogen is a well-established risk factor for breast cancer (BC). Despite a growing TG population, the risk of developing BC in TG persons is unclear and there is no consensus on how to ideally screen this undeserved population for BC. These knowledge gaps prevent informed decision-making among healthcare providers and TG persons, likely contributing to the cancer disparities observed in the TG community. The overarching goal of my research agenda is to develop evidence-based TG BC screening guidelines. The proposed K08 will begin to fill critical knowledge gaps. In collaboration with our LGBTQ+ Inclusion Health Clinic, we will establish a pilot BC screening program and utilize a mixed methods approach to explore BC risk and screening in this population. These data will provide the necessary foundation to develop a multi-institutional longitudinal TG BC screening cohort study which will inform the development of BC screening guidelines and best practices for BC screening within the TG community. The foundational K08 work will be accomplished through three specific aims: 1) determine the callback and biopsy rates of TG persons after screening mammography and automated breast ultrasonography, 2) assess perceptions towards BC risk, screening, and the screening experience of TG individuals through surveys and interviews, and 3) identify individual and systems-level barriers to BC screening for TG persons and methods to optimize the screening process through interviews and focus groups. These findings will provide the first-ever prospective scientific data on screening mammography and automated breast ultrasonography lesion detection in TG persons. The qualitative data from Aims 2 and 3 will identify individual and systems-level barriers to screening and opportunities to improve the screening process and experience. The research proposal is complemented by a comprehensive and distinctive training plan focused on mixed methods and survey research, gender studies, database development, and cohort recruitment and retention. In combination with my diverse and collaborative mentorship team, this study and training plan is designed to optimize my seamless transition to becoming an independently funded surgeon–scientist and my efforts to mitigate BC disparities in TG persons through a 3-step process. The novel pilot BC screening study (Step 1) will provide the necessary preliminary data and experience to submit an R01 application to develop a multi-institutional longitudinal TG BC screening program (Step 2) which will definitively establish the lifetime risk and incidence of BC to inform the development of evidence-based BC screening guidelines for TG persons and best practice guidelines (Step 3).