A large study provides reassurance for women taking hormone replacement therapy after menopause. (Breast Cancer Res Treat, 2008; 107: 103-111) Performed in France, the study involved follow-up of 80,000 post-menopausal women treated with varying formulations of hormones, or with no hormones. Average duration of follow-up was eight years.
Compared with women taking no hormones, the incidence of invasive breast cancer in women taking estrogen alone was 30% higher. However, in women taking estrogen plus bioidentical progesterone, there was NO increase in breast cancer incidence. Women taking artificial progestins had the worst results, a 69% increase in breast cancer incidence.
The type of estrogen used and the route of administration made no difference. The crucial factor was the type of progesterone used. Synthetic progesterone increased breast cancer risk, while bioidentical formulations lowered breast cancer incidence to the level of women taking no hormones whatever.
Allan Sosin, M.D.