LAUSR

Introduction: Breast cancer is the most common cancer in women. Women with personal history of breast cancer are at increased risk of second primary cancers including ovarian cancer. Bilateral salpingo-oophorectomy (BSO) is a well-established option for ovarian cancer risk reduction. However, the benefit of ovarian cancer risk reduction should be balanced against the health sequelae caused by the premature estrogen loss. We examined the associations between BSO after breast cancer diagnosis and long-term health outcomes, using large-scale linked electronic health records. Methods: We selected women diagnosed with invasive breast cancer before the age of 75 between 1995 and 2019 using data from the National Cancer Registration Dataset (NCRD), which describes all cancers registered in England. These women were linked to the Hospital Episode Statistics (HES) Admitted Patient Care (APC) dataset to identify the delivery of BSO, while the use of hormonal replacement therapy (HRT) was identified from the community dispensed prescriptions dataset. Long-term outcomes (e.g., ischemic heart disease) were selected from HES, and the NCRD provided data on second cancer diagnosis and all-cause mortality. Multiple imputation was used to impute missing data on stage, grade, hormonal receptor status and ethnicity. Women were followed from the date of breast cancer diagnosis to development of an outcome of interest or censoring or end of data collection. Multivariable Cox regression was used to examine the associations, with BSO modeled as a time-dependent covariate. The analysis was stratified by patient age at BSO (<55 and ≥55 years). Results: The study included 566,731 women, with median follow up time 8.40 (IQR: 4.4-14.5) years. Of those, 23,881 women had BSO after their breast cancer diagnosis. BSO before the age of 55 was not associated with all-cause mortality (hazard ratio (HR):1.03, 95%CI:0.98-1.08), while BSO after the age of 55 was associated with a small reduction in the risk of all-cause mortality (HR:0.93, 95%CI:0.89-0.99). BSO before and after the age of 55 was associated with increased risk of ischemic heart disease with HRs of 1.23(95%CI:1.07-1.41) and 1.13(95%CI:1.02-1.25), respectively. There was no association between BSO and cerebrovascular events (HR:0.97, 95%CI:0.82-1.15, for BSO under age 55, HR:0.96, 95%CI:0.87-1.07, for BSO after age 55). Ongoing analyses are investigating the associations stratified by the severity of cardiovascular outcome (fatal/non-fatal) and the use of HRT, and the associations with second cancers and neuropsychiatric outcomes. Conclusion: BSO after 55 does not appear to be associated with detrimental health effects in women diagnosed with breast cancer. Further examination of the associations between BSO and other long-term health outcomes and the influence of HRT in younger women is needed. Citation Format: Hend Hassan, Tameera Rahman, Andrew Bacon, Craig Knott, Isaac Allen, Catherine Huntley, Lucy Loong, Yvonne Walburga, Katrina Lavelle, Eva Morris, Steven Hardy, Bethany Torr, Diana M Eccles, Clare Turnbull, Marc Tischkowitz, Paul Pharoah, Antonis C. Antoniou. Long-term health outcomes of bilateral salpingo-oophorectomy in women with personal history of breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 988.