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A new scientific paper and other recent evidence offer important reassurances about the risk of breast cancer from hormone therapy to treat menopause symptoms, two University of Virginia School of Medicine menopause experts say.

Hormone therapy can help relieve menopause symptoms such as hot flashes, night sweats, sleep disturbances, vaginal issues, sexual problems, and loss of bone density. But information has been conflicting on whether or how much this treatment increases recipients’ risk of breast cancer.

The new review in the scientific journal Menopause, combined with other recent findings, provides much-needed clarity, according to UVA Health’s JoAnn V. Pinkerton, MD, and Carolyn S. Wilson, MD. Pinkerton and Wilson have outlined their thoughts on the review in an accompanying editorial co-written with Andrew M. Kaunitz, MD, of the University of Florida College of Medicine – Jacksonville.

“When prescribed to women after hysterectomy, estrogen therapy used alone at menopause did not increase the risk of invasive breast cancer. Longer durations of estrogen therapy use may increase risk. For women with an intact uterus who need combined estrogen and progestogen, the risk of breast cancer increased slightly and persisted after discontinuation,” said Pinkerton, professor of obstetrics and gynecology, director of midlife health at UVA Health and executive director emeritus of the North American Menopause Society. “Women and their healthcare providers should feel reassured about the safety of hormone therapy when used at menopause.”  

Hormone Therapy and Breast Cancer Risk

There have been longstanding questions about whether hormone therapy — including progestogens and estrogen together or estrogen alone — puts women at increased risk of breast cancer. The waters have been muddied by sometimes conflicting results from large observational studies and two large randomized Women’s Health Initiative (WHI) clinical trials.

The uncertainty prompted the authors of the new Menopause review to evaluate the differences between the trial data and the observational data. They set out to examine both the large WHI trials and smaller randomized controlled trials that could provide additional insight. 

Their results, Pinkerton and her co-authors say in the accompanying editorial, “make a strong case” that hormone therapy taken at menopause does not increase the risk of invasive breast cancer for women who have received a hysterectomy. 

The editorial notes that estrogen combined with progesterone increases breast cancer risk for women who have not undergone a hysterectomy, especially when used long-term. However, the authors point to another recent study indicating that the increased risk did not translate into a higher risk of death. “The lack of higher mortality with combined estrogen and progesterone therapy is reassuring for women with a uterus who have been concerned about using hormone therapy at menopause,” Wilson said. 

Further, the authors note that not all progestogens — medications that protect the uterus against estrogen-stimulated cancer — carry equal breast cancer risk. It appears that estrogen combined with micronized progesterone and dydrogesterone does not increase breast-cancer risk to the same degree as other combinations, if at all. (Though widely available in Europe and elsewhere, dydrogesterone has been discontinued in the United States in favor of other progestogens.)

The new paper and other recent findings offer important insights for patients and their doctors, the UVA menopause experts say. The editorial authors urge doctors to discuss the benefits and potential risks of the treatment with women when considering hormone therapy. They recommend that patients and their doctors reevaluate whether to continue the treatment periodically while continuing with breast examinations and breast imaging. 

“Let’s replace fear with knowledge,” Pinkerton said. “Most healthy women under age 60 or within 10 years of having their last period and having bothersome symptoms can take hormone therapy without fear at menopause if taking estrogen alone or combined with progesterone.” 

Editorial Published

Both the new review and the accompanying editorial have been published online by Menopause. Pinkerton is participating in a multicenter clinical trial of nonhormone therapy for hot flashes, for which UVA is receiving financial support from Bayer. Kaunitz noted that his institution receives financial support from Merck and Bayer for ongoing clinical trials.

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