Researcher: Estrogen-only therapy may prevent breast cancer in some women

Estrogen-only hormone replacement therapy may benefit younger postmenopausal women who do not have a uterus, a Canadian researcher said Thursday at the annual meeting of the San Antonio Breast Cancer Symposium.

Dr. Joseph Ragaz, an oncologist at the University of British Columbia, presented a re-analysis of the Women’s Health Initiative -- which originally concluded that both long-term estrogen-only and estrogen-plus-progestin hormone replacement were too risky for most women.

But Ragaz said his take on the data suggests that using only estrogen -- for women who do not have a uterus and do not need progestin -- protects against breast cancer. He found that subsets of women, such as younger postmenopausal women and those with no strong family history of breast cancer or benign breast disease, had a lower risk of breast cancer after using estrogen-only therapy and reaped other health benefits, such as a lower risk of heart disease.

Ragaz says studies are needed to determine whether estrogen produced by the body, called endogenous estrogen and which is known to fuel cancer growth, and outside sources of estrogen (called exogenous) have different effects on breast-cancer risk.

“Our conclusion, which is potentially a new paradigm, is that we see a dual effect,” Ragaz said. “On a research level, we have to identify the mechanisms or biology that would distinguish exogenous-estrogen benefits from the carcinogenic effects of the endogenous estrogen.”

The study was called “provocative” by Dr. Judy Garber, an associate professor of medicine at the Dana-Farber Cancer Institute. But she said the idea called for further study and that the current guidelines for women regarding hormone therapy shouldn’t change.

Related: Mammography guidelines fail to persuade women.

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