Menopausal hormone therapy and breast cancer risk

March 15, 2012, Journal of the National Cancer Institute

In the past decade, results from large prospective cohort studies and the Women's Health Initiative (WHI) randomized placebo-controlled hormone therapy trials have substantially changed thoughts about how estrogen alone and estrogen plus progestin influence the risk of breast cancer, according to a review published March 15 in the Journal of The National Cancer Institute.

Although is currently used by millions of women for , there is still concern about hormone therapy–induced risk. In addition, the effects of estrogen plus progestin vs estrogen alone on breast cancer are not completely understood.

To compare the effects of estrogen alone vs those of estrogen plus progestin on breast cancer risk, Rowan T. Chlebowski, M.D., Ph.D., of the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center and Garnet Anderson, Ph.D., at Fred Hutchinson Cancer Research Center at, looked at data from two randomized, placebo-controlled full scale clinical trials conducted in the WHI. One trial evaluated estrogen plus progestin in postmenopausal women with an intact uterus, and the other evaluated estrogen alone in postmenopausal women with prior hysterectomy. Estrogen plus progestin statistically significantly increased the risk of breast cancer. In contrast, estrogen alone use in postmenopausal women with a previous hysterectomy, statistically significantly decreased the risk of breast cancer.

The randomized clinical trial findings differ from the predominance of observational studies, which suggested that both estrogen alone and estrogen plus progestin increase breast cancer incidence. The authors propose that "an imbalance in the use of mammography with greater screening for hormone users could explain some of the increase in breast cancer incidence with estrogen alone seen in cohort studies because screened populations have more cancers detected than unscreened populations".

While the mechanisms underlying the different effects of estrogen alone and estrogen plus progestin are not completely understood, the authors state that preclinical and other clinical evidence suggests "the findings in the clinic, taken together with preclinical evidence, indicate that many breast cancers in post-menopausal women can survive only a limited range of exposures."

Explore further: Combo hormone therapy has increased breast cancer risk over estrogen alone

Related Stories

Combo hormone therapy has increased breast cancer risk over estrogen alone

November 18, 2011
The debate about using menopausal hormone therapies to relieve symptoms in post-menopausal women has been ongoing. Is the combination therapy of estrogen and progestin better or worse than just giving women estrogen alone? ...

Breast tenderness in women getting combo hormone therapy associated with increase in breast density

October 14, 2011
Post-menopausal women who experience new onset breast tenderness after starting combination hormone therapy may have an increased risk of breast cancer compared to women who don't experience breast tenderness, a study by ...

Breast tenderness linked to increased breast density

October 24, 2011
(Medical Xpress) -- Post-menopausal women who experience breast tenderness after starting combination hormone therapy have a higher risk of breast cancer than women who don't, a study by researchers with UCLA's Jonsson Comprehensive ...

Recommended for you

Scientists block the siren call of two aggressive cancers

January 23, 2018
Aggressive cancers like glioblastoma and metastatic breast cancer have in common a siren call that beckons the bone marrow to send along whatever the tumors need to survive and thrive.

Boosting cancer therapy with cross-dressed immune cells

January 22, 2018
Researchers at EPFL have created artificial molecules that can help the immune system to recognize and attack cancer tumors. The study is published in Nature Methods.

Workouts may boost life span after breast cancer

January 22, 2018
(HealthDay)—Longer survival after breast cancer may be as simple as staying fit, new research shows.

Cancer patients who tell their life story find more peace, less depression

January 22, 2018
Fifteen years ago, University of Wisconsin–Madison researcher Meg Wise began interviewing cancer patients nearing the end of life about how they were living with their diagnosis. She was surprised to find that many asked ...

Single blood test screens for eight cancer types

January 18, 2018
Johns Hopkins Kimmel Cancer Center researchers developed a single blood test that screens for eight common cancer types and helps identify the location of the cancer.

Researchers find a way to 'starve' cancer

January 18, 2018
Researchers at Vanderbilt University Medical Center (VUMC) have demonstrated for the first time that it is possible to starve a tumor and stop its growth with a newly discovered small compound that blocks uptake of the vital ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.