Estrogen-only therapy may protect certain women against breast cancer

Younger postmenopausal women without a uterus (post-hysterectomy) in need of hormone replacement for menopausal symptoms may also gain protection against breast cancer by taking estrogen-only hormone replacement therapy (ERT), the Los Angeles Times reports. This somewhat surprising finding was presented by Dr. Joseph Ragaz yesterday at the annual meeting of the San Antonio Breast Cancer Symposium after he re-analyzed data from the Women’s Health Initiative (WHI) aimed at determining the health effects of both estrogen-only and estrogen-progestin hormone replacement therapy. Originally, the WHI concluded that long-term use of both ERT and the combination HRT therapies posed a substantial health risk, particularly for breast cancer. Dr. Ragaz, however, found that certain subsets among the study participants, such as younger postmenopausal, post-hysterectomy women and those with no strong family history of breast cancer or benign breast disease, had a lower risk of breast cancer and other conditions such as heart disease after using ERT.

Prolonged exposure to estrogen produced by the body (endogenous estrogen) is a known risk factor for breast cancer, and whether estrogen replacement (exogenous estrogen) has a different effect on breast tissue has yet to be determined. ACSH’s Dr. Josh Bloom thinks that the mechanism is analogous to some extent to that of testosterone supplementation for men. “With testosterone, you see something similar. When you administer supplemental testosterone, it can be via a patch, gel or pill. The pill form has been known to cause liver cancer while the gel and patch have few side-effects. Perhaps, it could be that the pill is going straight to the liver, and thus causing problems there. Exogenous estrogen likely proceeds through a different metabolism in the body.”