Ovarian removal at or after benign hysterectomy and breast cancer: a nationwide cohort study

Purpose Large-scale population-based registry studies investigating the risk of breast cancer after removal of both ovaries at hysterectomy for benign conditions in women with no known genetic predisposition to cancer are needed. We aimed to perform such a study taking into account the age at surgery status and use of hormone replacement therapy (HRT).

Within the female population of Denmark born 1937–1996, we evaluated breast cancer incidence after unilateral or bilateral oophorectomy concomitant with or after benign hysterectomy in comparison with no surgery and with hysterectomy alone using health registry data during 1978–2016. In a subpopulation followed from 1996, the analyses were stratified according to use of HRT.

We found a reduced risk of breast cancer among women aged < 45 years at bilateral oophorectomy compared with women with hysterectomy alone (HR = 0.78; 95% CI 0.66, 0.92), whereas slightly increased risks were seen in women above 50 years. In the subpopulation, non-users of HRT aged ≥ 50 years at oophorectomy had a HR of 0.74 (95% CI 0.56, 0.98) for breast cancer after bilateral oophorectomy compared with hysterectomy alone.

Our large-scale study covering four decades provides evidence that bilateral oophorectomy performed at young age in women with benign indications for hysterectomy is associated with a reduction in breast cancer risk. The finding of a negative association at older ages in women not using HRT deserves further attention. Similar content being viewed by others Data availability The datasets generated and analyzed during the current study are not publicly available, since the authors do not have permission to share the data.

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The authors would like to thank Lea Elsborg Olsen and Rasmus Hertzum-Larsen for help with data management. Funding This work was supported by the Danish Cancer Society's Scientific Committee (KBVU) (Grant No. R167-A11019-17-S2). Author information Authors and Affiliations Corresponding author Ethics declarations Conflict of interest Lene Mellemkjær has an immediate family member employed at Novo Nordisk, and has an immediate family member who owns stocks in Novo Nordisk. The other authors declare that they have no conflicts of interest. Ethical approval In Denmark, approval from the Ethical Committee System is not required for studies that are entirely register based. Informed consent In Denmark, written consents are not required for studies that are entirely register based. Additional information Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Electronic supplementary material Below is the link to the electronic supplementary material. Rights and permissions About this article Cite this article Gottschau, M., Kjær, S.K., Settnes, A. et al. Ovarian removal at or after benign hysterectomy and breast cancer: a nationwide cohort study. Breast Cancer Res Treat 181, 475–485 (2020). https://doi.org/10.1007/s10549-020-05628-z Received: Accepted: Published: Version of record: Issue date: DOI: https://doi.org/10.1007/s10549-020-05628-z