Hormone therapy and risk of ovarian cancer in postmenopausal women: a systematic review and meta-analysis

Objective:Our objective was to perform a meta-analysis examining the risk of ovarian cancer with different types and regimens (continuous or sequential) of hormone therapy (HT).Methods:PubMed, Cochrane, and Embase databases were searched until December 2014 using the terms: HT, estrogen therapy (ET), ovarian cancer, postmenopausal, and menopausal. HT was considered unopposed ET, estrogen-progestin therapy (EPT), or ET+EPT (ET followed by EPT).Results:Of 180 studies identified, 12 were included in the meta-analysis. Of the 12 studies, 9 were cohort studies including 2,350,546 women and 7,549 cases of ovarian cancer, and 3 were case-control studies including a total of 1,347 cases and 2,052 controls. ET, EPT, and ET+EPT were associated with an increased risk of ovarian cancer: pooled hazard ratio (HR)/relative risk (RR)=1.37, 95% CI: 1.19 to 1.58, P<0.001; pooled HR/RR=1.27, 95% CI: 1.18 to 1.36, P<0.001; pooled HR/RR=1.55, 95% CI: 1.05 to 2.30, P=0.027, respectively. Continuous and sequential regimens were associated with an increased risk: pooled HR/RR=1.27, 95% CI: 1.04 to 1.54, P=0.018; pooled HR/RR=1.31, 95% CI: 1.08 to 1.58, P=0.006, respectively. HT was associated with an increased risk of serous ovarian cancer (pooled HR/RR=1.46, 95% CI=1.28-1.67, P<0.001), but not clear cell, endometrioid, or mucinous ovarian cancer.Conclusions:Hormone therapy, regardless of type or regimen, is associated with an increased ovarian cancer risk.