The link between hormone replacement therapy (HRT), also called menopausal hormone therapy (MHT), and breast cancer isn't new. Now a new, large-scale study, published in The Lancet confirms an increased risk of breast cancer from all types of MHT except one—topical vaginal estrogens—that can persist for more than 10 years after a woman stops therapy.
As women enter and sustain menopause, levels of the hormones estrogen and progesterone decline. As the North American Menopause Society (NAMS) explains, estrogen promotes the growth and health of the female reproductive organs and keeps the vagina moisturized, elastic and stretchy, and well supplied with blood. Progesterone prepares the lining of the uterus for a fertilized egg and helps maintain early pregnancy. Many women receive synthetic hormones via pill, cream or gel, patch, or injection.
After taking a deep dive into both published and unpublished work on menopause and MHT, the study’s researchers determined that breast cancer risk increases with the use of estrogen-progestagen hormone therapy when compared to use of estrogen-only therapy. Progestagens are synthetic hormones that mimic the actions of natural progesterone, the authors explain.
Frequency mattered, and risk was higher for women who used estrogen-progestagen therapy every day instead of several days a month.
Lots of Women Use Lots of Hormones
The research from a very long and impressive list of global researchers that comprise the Collaborative Group on Hormonal Factors in Breast Cancer shares that currently, some 6 million women use MHT in North America and 6 million do so in Europe.
Regulatory agencies on both continents—here, it’s the U.S. Food & Drug Administration—tend to recommend use for the shortest time possible, but guidelines in general can be nebulous. The latest guidelines in UpToDate explain that both NAMS and the American College of Obstetrics and Gynecology agree that use of MHT should be individualized and not discontinued solely based upon patient age—again, every women is different, and it’s important to discuss all the risks and benefits with a doctor. Apparently 5 years of use is common now, cutting back the 10 years that was formerly more common, they say.
This major study analyzed data from more than 58 smaller studies of more than 100,000 women diagnosed with breast cancer—51% had used MHT. The authors looked at data from 1992 to 2018 that recorded MHT use and tracked the rates of breast cancer.
Longer Use Doubled Risk
Using MHT for 10 years resulted in about twice the excess breast cancer risk associated with five years of use, says study co-author Gillian Reeves a professor of statistical epidemiology from the University of Oxford, U.K. Using MHT has little increased risk following use of less than a year. Topical use of vaginal estrogens delivered as creams or suppositories does not appear to increase risk.
The authors determined that use of MHT was more strongly associated with estrogen-receptor-positive (ER+) breast cancer than other types. Hormones mainly affect the ER+ type of breast cancer, they say. They also said that the age groups of 40s and 50s presented the most evidence, since those are the decades when most women experience menopause and thus are prompted to use MHT. There appeared to be less risk among a smaller group of women who began using MHT in their 60s.
In this study, which focused on women of normal weight, being severely overweight or obese didn’t really add to breast cancer risk, especially if women used estrogen-only MHT, the authors say. Being obese has previously been shown to increase risk in post-menopausal women. Estrogen-only therapy is typically used by women after a hysterectomy.
What This Study Means for You
If your head spins when you contemplate the risks and benefits of MHT, you're not alone, because still, the use of hormone therapy is not an exact science.
As Joanne Kotsopoulos, Ph.D., of the Women's College Research Institute in Toronto, Ontario wrote in a comment in the same edition of The Lancet, menopause for many women involves insomnia, hot flashes, and a general "decline in wellbeing." No wonder women seek relief.
On the other hand, the prospect of developing breast cancer gives many women—and their physicians pause. As Dr. Kotsopoulos wonders out loud, maybe breast cancer worry has meant millions of women suffered menopause symptoms needlessly. That's another reason knowing "cancer risks with accuracy" is so important, and because not using MHT may increase risk of osteoporosis, poor heart health, or cognitive decline, she says.
In summary, "Clinicians must heed the message of this study but also to take a rational and comprehensive approach to the management of menopausal symptoms, with careful consideration of the risks and benefits of initiating MHT for each woman," she adds.
It's important to have frank and collaborative discussions with your ob-gyn. Every single woman is different, and that includes you. If it's true that, "the more you know…," this latest research adds to a body of work that should help women make more informed decisions.
About Going 'Hormone-less' Naturally With Menopause
You're probably wondering, "So what do I do now?" For sure, don't rush into anything. The National Center for Complementary and Integrative Health (NCCIH) says these popular alternatives to managing menopause may help case-by-case, but they have not been backed by extensive or comprehensive scientific research:
Natural products: Although we may hear news to the contrary, phytoestrogens or dietary estrogens that occur naturally in plants and plant-based foods, along with herbs—including black cohosh—and other natural products, don't really help us with menopause symptoms. Before you try anything, talk to your doctor.
Hypnotherapy and mindfulness meditation: We may get some relief with hypnotherapy and mindfulness meditation, but there's not a ton of research to back this up.
Acupuncture: The results around acupuncture, a form of Chinese medicine, for treating menopause symptoms just aren't totally convincing, but NCCIH is doing more research.
Yoga: Practicing yoga and other exercises may help with some other symptoms of menopause, but not hot flashes.
Bioidential hormones: These are usually referred to as custom-compounded hormones that are “prepared” by a pharmacist on an individual basis, NAMS says. These aren't proven to be safer or more effective than conventional hormone therapy, and their preparation isn't overseen by a regulatory agency.
Doctors and other women say that staying "balanced," with a healthy diet, plenty of exercise, and strong social connections all go a long way toward managing your menopause.