Abstract
OBJECTIVES: Improved breast cancer (BC) outcomes highlight the importance of secondary primary cancers (SPCs) on survivor prognosis. The objective of this study was to investigate the potential genetic association between primary BC and ovarian cancer (OC), laying the groundwork for the development of preventive strategies for SPC-OC following BC surgery. METHODS: This study aimed to assess the connection between BC and OC using a two sample Mendelian randomization (MR) approach, exclusively employing aggregate level data from publicly available genome wide association studies (GWASs). Finally, the Genetic Risk Scores (GRS) method was used for secondary analysis to verify the results robustness further. RESULTS: The IVW method revealed a genetic correlation between Overall BC and ER + BC with Serous borderline tumors, while ER-BC exhibited genetic correlation with Mucinous borderline tumors and high-grade serous ovarian cancer. The findings from the GRS method aligned with those of the primary analysis, reinforcing the study's robustness. CONCLUSION: Our MR Study identifies an association between BC and OC, highlighting the importance of increased vigilance in clinical practice for individuals with a history of BC. Timely intervention and treatment measures should be taken when necessary.