SAN ANTONIO, Dec. 10 (UPI) — Hormone replacement therapy that uses estrogen alone provides a protective effect in reducing breast cancer risk, U.S. researchers say.

“Our analysis suggests that, contrary to previous thinking, there is substantial value in bringing hormone replacement therapy with estrogen alone to the guidelines,” lead researcher Dr. Joseph Ragaz of the University of British Columbia in Vancouver says in a statement.

Ragaz and colleagues reviewed and re-analyzed data from the Women’s Health Initiative hormone replacement therapy trials — a trial ended in 2002 when subjects with estrogen plus progestin had a greater incidence of coronary heart disease, breast cancer, stroke and pulmonary embolism than the subjects receiving placebo.

The researchers found that subsets of women with no strong family history of breast cancer who received estrogen alone had a significantly reduced breast cancer incidence while 75 percent without benign disease prior to the trial enrollment also had a reduced breast cancer risk.

“While the use of hormone replacement therapy with estrogen alone may reduce the risk of breast cancer and may also be appropriate to manage menopausal symptoms, further research is warranted to elaborate on the optimum treatment regimen, to refine the selection of ideal candidates for estrogen therapy, and to understand the estrogen mechanisms that support the prevention of human breast cancer,” Ragaz said.

The findings were presented at the 33rd annual Cancer Therapy & Research Center and the American Association for Cancer Research Breast Cancer Symposium in San Antonio.