Bioidentical hormones are again shown be superior to synthetic hormones, and this is continuing proof that bioidentical hormones are not associated with breast cancer while synthetic versions significantly increase the risk of breast cancer.

Unequal risks for breast cancer associated with different hormone replacement therapies: results from the E3N cohort study. Fournier A, Berrino F, Clavel-Chapelon F. Breast Cancer Research and Treatment 2007

One of the largest studies to date comparing the risk of breast cancer with the use of natural bioidentical hormones and synthetic hormone replacement therapy demonstrates that the natural hormones have significantly less associated risk of breast cancer. This study published a 2007 issue of Breast Cancer Research reported the association between various forms of HRT and the incidence of breast cancer in over 80,000 postmenopausal women who were followed for over 8 postmenopausal years. This study found that, compared to women who never used any hormone replacement therapy, women who used estrogen only (different preparations analyzed together) had an increased risk of breast cancer that was 1.29 times those who never used estrogen. If a synthetic progestin was used in combination with estrogen, there was a significant increase in the risk of breast cancer compared to those on the estrogen only that was 1.69 times the risk of those who never used estrogen.

If, however, a woman used natural progesterone in combination with estrogen, the increased risk of breast cancer was eliminated, having no increase risk o f breast cancer as compared to those who never used estrogen. In addition, estriol containing products was found to have a further protective effect against breast cancer, resulting in a lower risk of breast cancer than even those who did not use any hormone replacement.

This study adds to the mass of previous medical literature that demonstrates the superior safety of bioidentical hormone replacement as compared to synthetic hormones.