Breast cancer risk in relation to different types of hormone replacement therapy in the E3N-EPIC cohort.

Authors: Fournier A, Berrino F, Riboli E, Avenel V, Clavel-Chapelon F.

Publication Year: 2005

Citation: Int J Cancer 2005; 114(3):448-54.

Combined HRT with estrogen (either oral or transdermal) and synthetic progestins was found to carry a significantly increased risk of breast cancer compared with estrogens plus oral micronized progesterone.  In fact, no increase in breast cancer risk was seen in the estrogen plus oral micronized progesterone group compared with estrogen alone.  This large multi-center study therefore suggests that there is a dramatic difference between the effects of bioidentical progesterone versus synthetic progestins on breast cancer risk.