Chains of evidence, mosaics of data: does estrogen 'cause' breast cancer? How would we know?

Menopausal hormone therapy: why we should no longer be afraid of the breast cancer risk

The threat that women may develop breast cancer is the major reason why both physicians and women are afraid to use menopausal hormone therapy (MHT). The fear pertains to estrogen-progestin replacement therapy (EPRT) as estrogen-alone replacement therapy has no, or even a reduced, breast cancer risk. We reviewed the way breast cancer risk with EPRT was reported in some major publications since 2002 and tried to put the use-risk association in context. We hope this will make it easier for the physician and the menopausal woman to understand the risk involved and allow more confident and more informed decision-making regarding MHT use. We conclude that there are five interrelated reasons why physicians and women should no longer be afraid of the breast cancer risk with EPRT. We submit that breast cancer related to EPRT use is rare because the risk is very low; the reported increase in breast cancer risk with EPRT is not relevant to current practice; modifiable lifestyle factors, not EPRT, are the real risks for breast cancer; breast cancer-specific mortality is reduced in women who develop breast cancer while on EPRT; and avoiding MHT use when indicated puts a woman in harm's way.