Abstract The improvement in breast cancer survival is partially due to improvements in treatments. However, these treatments are not without mild to life-threatening side effects. For example, anthracycline chemotherapies (e.g. doxorubicin) and human epidermal growth factor receptor-2 (HER-2) targeted therapies have been shown to cause cardiotoxicity (CTX), or damage to the heart. This side effect is of great concern as survivors are more likely to die of heart disease than any other diagnosis and racial disparities exist with regard to prevalence of CTX and risk of heart-related mortality. Factors that have been shown to contribute to cardiotoxicity include Black race and the presence of comorbidities. While the cardiovascular disease literature includes the roles of psychosocial and sociocultural factors in its prevalence and the racial disparity in its manifestation and progression, these factors are unexplored in the context CTX. Additionally, cancer care delivery factors, including maintenance of CTX, deserves attention as there may be opportunities to address gaps or differences in care that may exacerbate the CTX disparity. Addressing psychosocial and sociocultural factors may provide intervention targets to mitigate CTX disparities. Guided by the Social Ecological Model, I will conduct retrospective analyses and a historical-prospective cohort study to identify factors related to the racial disparity in CTX. During the K99 mentored phase, I will abstract electronic hospital data on breast cancer survivors treated with anthracycline chemotherapy or Her-2 targeted therapies to elucidate sociodemographic, clinical, and maintenance factors that relate to onset of and racial differences in CTX (Aim 1). In Aim 2, I will conduct in-depth interviews with Black and White survivors (n=20) with and without CTX to understand psychosocial and sociocultural experiences that may contribute to CTX. During the R00 phase (Aim 3), I will use the information learned from the in-depth interviews to inform a survey that will be distributed to n=150 Black and White breast cancer survivors who were treated with adjuvant therapies. This survey, coupled with medical record data, will be used to assess relationships between psychosocial and socio-cultural factors and racial differences in CTX. In order to successfully execute these aims the candidate will receive strategic planning in cancer care delivery, cardio-oncology, and mixed methods research. These training aims will ensure the candidate's goal of successfully transitioning to independence and establishing a research program involving the development of interventions that will address racial disparities in cancer care delivery and outcomes. The expertise and guidance of the mentoring and advisory teams in addition to the wealth of resources and commitment to training provided through the institutional environment will ensure the success of the candidate's research project and transition to independence.

Narrative Cardiotoxicity (CTX), a side effect of breast cancer treatments such as anthracycline chemotherapy and human epidermal receptor-2 (HER-2) targeted therapies, is more prevalent in Black breast cancer survivors than in White breast cancer survivors; however, causes of this racial disparity are not fully understood. This study will leverage hospital data and will interview breast cancer survivors diagnosed with CTX to inform a survey that will aid in the identification of drivers of the racial disparity in CTX, namely, psychosocial and socio-cultural factors that have been explored in the cardiovascular literature but are novel to the cardio-oncology space. Findings from this study may offer opportunities to develop multilevel interventions seeking to improve outcomes in Black breast cancer survivors by addressing the racial disparity in CTX.