Breast Cancer Risk After Hysterectomy: A Health Insurance Database-Based Analysis.

Purpose: Despite numerous previous studies, the relationship between hysterectomies and breast cancer risk remains unclear. This study aimed to assess whether hysterectomies are significantly associated with a reduced risk of breast cancer in Korean women using data from the National Health Insurance Service database of South Korea.

Methods: We conducted a retrospective cohort study of South Korean women aged 40-59 years who underwent hysterectomies for benign reasons or underwent a health check-up between 2003 and 2011. To minimize confounding factors, a 1:1 propensity score matching (PSM) was used to balance the groups based on key covariates. The participants were followed up until December 31, 2020. Stratified Cox proportional hazards regression analysis was performed to assess the association between hysterectomies and breast cancer risk.

Results: After 1:1 PSM, 13,148 women were assigned to the hysterectomy or non-hysterectomy groups. Breast cancer occurred in 242 (1.8%) and 233 (1.8%) women in the non-hysterectomy and hysterectomy groups, respectively (p = 0.711). After adjusting for confounders, hysterectomy with or without adnexal surgery was not significantly associated with breast cancer risk (hazard ratio [HR], 0.937; 95% confidence interval [CI], 0.775-1.132 for hysterectomy with/without adnexal surgery; HR, 0.957; 95% CI, 0.779-1.176 for hysterectomy without adnexal surgery; and HR, 0.833; 95% CI, 0.513-1.353 for hysterectomy with adnexal surgery). No significant association was found when analyzing surgical methods or age at natural menopause.

Conclusion: Our study found no association between hysterectomies and breast cancer risk, which is consistent with previous studies that reported a null association.