Does Hormone Replacement Therapy Really Cause Cancer?

What We Were Told vs. the Truth

Photo by Anastasia Lenova

When I first started experiencing symptoms of perimenopause, I didn’t think too much about what I could do to mitigate them. At the time, all women were told that hormone replacement therapy, or HRT, caused breast cancer. Since there was a high incidence of breast cancer in my family, I knew that HRT was clearly off limits for me.

Fortunately, I managed pretty well without hormones. My hot flashes weren’t too bad, and I never experienced night sweats. I gained some weight but wasn’t plagued with brain fog. Looking back on it, the experience could have been a lot worse.

But what about those women my age (60s and 70s) who struggled during perimenopause and menopause? Hormones probably would have helped a lot. Not only were hormones not offered, they also weren’t even discussed. Women had few options back then.

The reason lies in the response of the Women’s Health Initiative (WHI) to a study they were conducting testing the effectiveness and safety of HRT. The study, started in 1992, was one of the first specifically about women’s health undertaken by the National Institutes of Health. It was also one of the most expensive, costing $1 billion.

The study progressed until 2002, when something extraordinary happened. Calling a press conference even before a paper had been published, the study leaders announced that they were stopping the study early. They claimed that the findings showed that HRT causes breast cancer, and they wanted to make the public aware of this information as soon as possible. In their view, it was urgent that women stop taking HRT immediately.

The announcement caused a flurry of media coverage and an atmosphere of fear and confusion. The headline in the New York Times was “Study Halted Over Increase in Cancer Risk.” Women were terrified, frantically calling their doctors for reassurance that a breast cancer diagnosis wasn’t imminent. Everyone assumed that this group of well-respected researchers and physicians had found out something important. No one questioned or challenged their findings.

As it turns out, the medical community would have been wise to take a closer look at the data before spreading the word. In fact, the study leaders were wrong. Unbelievably, they had misinterpreted their own data. What this meant in practical terms was that menopause care was set back 20 years and that women now in their 60s and 70s missed out on any opportunity for hormone therapy.

Uncovering the Story

I first became aware of this story through a documentary called “Balance: A Perimenopause Journey,” sent to me by Jules, a subscriber to my Substack. The documentary, which I watched as a series of four episodes on Amazon Prime, follows two Jain monks as they look for relief from their perimenopausal symptoms. The series features stories from patients, some illustrating the difficulties they had finding doctors who understood their symptoms and could treat them, along with commentary from many experts in the field. Episode 2, however, stopped me in my tracks. Called “The Misinformation Crisis,” it laid out in clear, easy-to-understand language what the WHI said and what the facts really showed.

According to Dr. Kristi Funk, a breast cancer surgeon and founder of the Pink Lotus Breast Cancer Center in Los Angeles, the WHI claimed that the study showed a 26% increase in breast cancer cases. But if you dig into the data, as has been done over the past 20 years, the findings look quite different. For example, at the time, 4 out of 1,000 women received a breast cancer diagnosis, which corresponds to the number in the placebo group who were also diagnosed. On the other hand, among the group receiving a combination of estrogen and progesterone, 5 out of 1,000 women were diagnosed with breast cancer, a difference of 0.1%. This number was not considered statistically significant. Further, Dr. Heather Hirsch, a menopause expert also featured in the show, pointed out that women only on estrogen actually experienced a decline in breast cancer diagnoses.

Listening to these experts talk, I couldn’t understand why the data had been misconstrued. Looking for more answers, I went back to the Internet and found a treasure trove of information. An episode of a podcast called Unpaused, started by Dr. Mary Claire Haver, a leader in the menopause movement and another physician featured in the Balance documentary, called “The Truth About Estrogen: What the Women’s Health Initiative Got Wrong with Dr. Avrum Bluming & Dr, Carol Tavris,” provided a new interpretation of the data.

Here are a few key points from their review:

· A fact that was not well publicized at the time was that the average age of the participants was 63—more than 10 years older than the age most women are when they would be starting HRT. About 70% of the women were significantly overweight, and 50% were obese. Nearly 50% were previous or current smokers, and more than 35% had hypertension. This population is not representative of most women seeking HRT and certainly not the best experimental group.

· Nineteen years after the study was stopped, WHI investigators reported a 23% decreased incidence of breast cancer among women taking estrogen alone. Furthermore, the researchers noted that women who received estrogen and progesterone had no statistically significant increase in breast cancer mortality, while women taking estrogen alone had a 40% reduced risk of death due to breast cancer.

· HRT has a positive effect on cardiovascular health. A consensus has now emerged that starting HRT within the first 10 years of menopause is the time to maximize the benefits of HRT. Similarly, HRT can help maintain bone health and reduce fractures by 30-50%.

Bluming and Tavris had some thoughts about why this major mistake occurred—and why the WHI’s erroneous interpretations continue to be discussed today. They think that money may have had something to do with it; after all, the WHI was one of the most expensive studies ever funded. Also, bad news is big news. Back then, that meant more newspapers and magazines sold and more people tuning in to watch coverage about these findings.

Other ideas were also mentioned. Fear of legal culpability on the part of physicians, disregard for women among physicians, and perhaps the one that made the most sense to me: the fact that the WHI was simply too big to fail. These top leaders in the field did not want to admit that they were wrong, and because of who they are, they don’t have to. (For the record, the WHI has walked back its initial claim that HRT causes ovarian and lung cancer. They also acknowledge that HRT helps prevent osteoporosis.)

New research has helped show the risks and benefits of HRT in a more positive light. One of the biggest findings is that for women who go through menopause before age 45, hormone therapy is recommended because these women are at a great risk of osteoporosis. For healthy women in their 50s, the increased risk of blood clots and stroke are rare, making this group good candidates for treatment.

Other benefits of HRT have surfaced. In an excellent article by Susan Dominua called “Women Have Been Misled About Menopause,” she pointed out that women who have taken hormones have 24% fewer bone fractures, a 20% lower incidence of diabetes, and no difference in overall mortality compared to women who did not.

Nonetheless, the legacy of the aborted WHI study endures. Even after 20 years, the world’s best journals, including JAMA, Lancet, and the New England Journal of Medicine, still refuse to publish articles about HRT. Education for rising physicians about menopause has not improved significantly, leaving many doctors unprepared to have comprehensive, nuanced conversation with their patients. As a result of these ongoing issues, the number of women in the United States taking hormones stands at 4% compared to the 40% taking them before the WHI press conference.

It’s easy to glaze over when reviewing the data associated with WHI and menopause. It’s hard to lay people to absorb this information. But what this story makes clear is that communication about hormones and menopause continues to be poor. I’m a science writer with a strong interest in women’s health and I wasn’t aware of this issue before watching the documentary. Jules also knew nothing about it, along with the women in my circle I asked about it. Most thought that hormones caused breast cancer and were visibly shocked when I told them otherwise.

I’m deeply disturbed that accurate medical information is buried and that old myths have such staying power. It makes me wonder if the public is being misled about other studies on issues such as dementia. I was already skeptical about coverage on science topics, but now I don’t know what to think. I think that every headline deserves additional research, especially if it sounds either catastrophic or too good to be true. In those instances, it’s likely that neither is true.