Progestins and progesterone in HRT & the risk of breast cancer
Controlled studies and most observational studies published over the last 5 years suggest that the addition of synthetic progestins to estrogen in hormone replacement therapy (HRT), particularly in continuous-combined regimen, increases the risk of breast cancer (BC) compared to estrogen alone.
In this important review of the literature on HRT and the risk of breast cancer, Campagnoli and collegues at the Sant Anna Gynecological Hospital in Torino, Italy conclude that the balance of the in vivo evidence is that progesterone does not have a cancer promoting effect on breast tissue. We therefore suggest that when HRT is indicated, preparations containing progesterone, and not a synthetic progestin should be used, according to a sequential or cyclic-combined regimen. In this way the risk of endometrial cancer is minimized without increasing the risk of breast cancer.
