Estrogen-Only Therapy Reduces Breast Cancer Chances In Post-Menopausal Women
March 7, 2012

Estrogen-Only Therapy Reduces Breast Cancer Chances In Post-Menopausal Women

A new study published this week shows that women who used estrogen alone as hormone replacement therapy after menopause had a lower risk of developing breast cancer up to five years after they stopped taking it, reports Shari Roan for the Los Angeles Times.

This discovery adds yet another twist to the ongoing story on hormone replacement therapy for treatment of hot flashes and poor sleep quality.

The estrogen-only therapy appears to cut the risk of having breast cancer by about 20 percent and significantly reduces a woman´s risk of dying from the disease and the benefits appear to last for years after the therapy has concluded, reports Brenda Goodman, MA, for WebMD.

Executive director of the North American Menopause Society (NAMS), Margery Gass, MD, explained to Goodman: “certainly for some women hormone therapy dramatically improves their quality of life.”

The report is a follow-up analysis of the landmark Women´s Health Initiative, a clinical trial of tens of thousands of women that began in 1993. That study compared two hormone replacement therapies, estrogen plus progestin, which most women must take, and estrogen alone, taken by women who have had hysterectomies.

The double-hormone arm of the study was abruptly halted in 2002 after scientists found that it raised the risk of breast cancer without conferring hoped-for benefits on the heart.

In 2004, the estrogen-alone arm of the study was also halted after researchers discovered an increased risk of stroke and blood clots. At the time, it was not clear how estrogen alone affected breast cancer risk, however research since then found that estrogen alone did not increase risk and maybe even lowered it.

This latest study, published in the journal Lancet Oncology, provides the strongest evidence yet that estrogen alone not only lowers breast cancer risk for a sustained time for some women, it also decreases mortality for the disease.

Study coauthor Dr. Rowan T. Chlebowski, an investigator at the Los Angeles Biomedical Research Institute in Torrance and chief of medical oncology and hematology at Harbor-UCLA Medical Center, told the LA Times reporter, “It´s a very interesting finding.”

“It goes against a huge number of observational studies suggesting estrogen would increase the risk of breast cancer by itself. But this study points out that it´s much more complex than we originally thought. Estrogen alone for the period we studied seems to be pretty safe and maybe even beneficial.”

Researchers studied more than 7,500 postmenopausal women who had undergone a hysterectomy and had taken estrogen-only HRT as a part of the Women´s Health Initiative, writes Liz Szabo for USA Today. The women, aged 50 to 79, took estrogen for six years and then stopped when the trial was halted.

Researchers continued to monitor the women for the next five years and found that the women who took estrogen were 23 percent less likely to develop breast cancer than those who took a placebo, reports Carrie Gann for ABC News.

Of the women taking estrogen-only HRT who did develop breast cancer, the study found that they were less likely to die from the disease. Six women taking estrogen died of the disease, compared with 16 in the group taking a placebo.

“There´s no question that hormones remain the best treatment for hot flashes and night sweats,” says Dr. Janet Pregler, director of the Iris Cantor-UCLA Women´s Health Center. “The risk of doing that for a few years around menopause is really very low, depending on other health risks you have.”

The study found several caveats to the effectiveness of estrogen-only HRT. The reduced risk of breast cancer applied only to women who were not already at risk for the disease. As a result, patients should not take estrogen with the goal of reducing breast cancer risk.

Also, HRT is still associated with an increased risk of stroke, and doctors say that women who are at increased risk of stroke and blood clots should still avoid taking any HRT.


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