Hysterectomy and risk of epithelial ovarian cancer by histologic type, endometriosis, and menopausal hormone therapy

Abstract

Purpose This nationwide, register-based case-control study investigated the association between hysterectomy and risk of epithelial ovarian cancer according to histology and by history of endometriosis and MHT use. Methods From the Danish Cancer Registry, all women registered with epithelial ovarian cancer during 1998‒2016 were identified (n = 6,738). Each case was sex- and age-matched to 15 population controls using risk-set sampling. Information on previous hysterectomy on benign indication and potential confounders was retrieved from nationwide registers. Conditional logistic regression was used to calculate odds ratios (ORs) with 95% confidence intervals (CIs) for the association between hysterectomy and ovarian cancer according to histology, endometriosis, and use of MHT. Results Hysterectomy was not associated with risk of epithelial ovarian cancer overall (OR = 0.97; 95% CI 0.88‒1.06) but was associated with reduced risk of clear cell ovarian cancer (OR = 0.47; 95% CI 0.28‒0.78). In stratified analyses, decreased ORs associated with hysterectomy were seen in women with endometriosis (OR = 0.73; 95% CI 0.50‒1.09) and in non-users of MHT (OR = 0.87; 95% CI 0.76‒1.00). Conclusion Hysterectomy was not associated with epithelial ovarian cancer overall but with reduced risk of clear cell ovarian cancer. Our findings may suggest a reduced risk of ovarian cancer after hysterectomy in women with endometriosis and in MHT non-users, but the statistical precision of our results did not allow firm conclusions.