Estradiol therapy and breast cancer risk in perimenopausal and postmenopausal women: a systematic review and meta-analysis.

AbstractObjective: To investigate the association between estradiol therapy and incidence of breast cancer, taking into consideration of different types of combined progestogen, the duration of exposure and the type of regimen.Method: A systematic review and meta-analysis.Result: A total of 14 studies were included in our study. In estradiol-only therapy analysis, meta-analysis resulted a pooled OR =0.90, 95% CI (0.40, 2.02) from the RCTs and pooled OR = 1.11, 95% CI (0.98, 1.27) from observational studies. However, in the analysis of estradiol-progestogen therapy, the risk of breast cancer varies according to the type of progestogen and the duration with more than five years (OR = 2.43, 95% CI (1.79, 3.29)) presented a higher risk than using less than five years (OR = 1.49, 95% CI (1.03, 2.15)).Conclusions: Estradiol-only therapy carries no risk for breast cancer, while the breast cancer risk varies according to the type of progestogen. Estradiol therapy combined with medroxyprogesterone, norethisterone ...