To systematically evaluate the risk of estrogen use and ovarian cancer in postmenopausal women.

PubMed, Cochrane, Embase databases and Chinese databases such as CNKI, VIP, and Wan fang were searched by computer. Studies on the correlation between estrogen replacement therapy and ovarian cancer in postmenopausal women up until January 2023 were collected. The methodological quality of the study was evaluated by Stata software and the effective data were extracted for meta-analysis. We used the odds ratio (OR) and its corresponding 95% confidence interval (CIs) to evaluate the relationship between hormone replacement therapy and ovarian cancer. When there was statistical heterogeneity between studies (P≤0.1 and I²≥ 40%), random effect model was used for meta-analysis; otherwise, fixed effect model was used for analysis.

A total of 14 retrospective studies including 10 cohort studies and 4 case-control studies were identified. Meta-analysis showed that postmenopausal estrogen therapy increased the risk of ovarian cancer in women (OR=1.27, 95%CI: 1.14-1.43). Stratified analysis showed that there was no significant increase in the risk of ovarian cancer in postmenopausal women who took estrogen for less than 5 years (OR=1.04, 95%CI: 0.90-1.20). Postmenopausal women who received estrogen treatment for 5 to 10 years had a significantly increased risk of developing ovarian cancer (OR=1.27, 95%CI: 1.06-1.53). Postmenopausal women who had been treated with estrogen for more than 10 years had a significantly increased risk of ovarian cancer (OR=1.69, 95%CI: 1.42-2.02).

The risk of ovarian cancer in postmenopausal women treated with estrogen replacement therapy is related to the course of estrogen therapy. There is no significant increase in the risk of ovarian cancer within 5 years, but the risk of ovarian cancer is significantly increased when the course of treatment exceeds 5 years.