Is There New Evidence Linking HRT to Breast Cancer?

If you suffer from menopausal symptoms, you may hear hormone replacement therapy (HRT).

What Is Hormone Replacement Therapy?

During menopause, estrogen levels decline. Women may experience discomforts like hot flashes and vaginal dryness. HRT is the most effective treatment for menopause symptoms. This treatment includes estrogen therapy and combination therapy of estrogen and progestin.

What Are Side Effects of HRT?

What Are More Serious Health Risks?

HRT has been linked to an increased risk of three types of cancers:

  • Breast cancer
  • Ovarian cancer
  • Womb cancer

It also increases risk of blood clots, heart disease, strokes, pulmonary embolism, and uterine fibroids.

Is There Research Data Linking HRT to Cancer?

The answer is “Yes.” Using the keywords “HRT” and “cancer” to search PubMed, there are 2,250 scientific papers. If we change the keyword from “cancer” to “breast cancer,” there are 1,395 scientific papers. Thus, 62% of all HRT-related cancer studies focused on breast cancer.

A recent study by scientists at Harvard University provided new evidence indicating that estrogen not only promotes but also directly causes breast cancer. This new discovery further confirms the cancer risk associated with estrogen. 

There were two classical studies linking HRT to breast cancer. These studies had large women populations. One in the US called “Women’s Health Initiative (WHI).” The other was in the UK called the Million Women Study.

In 1991, the NIH launched the WHI. More than 160,000 post-menopausal women ages 50 to 79 participated in the 15-year study. WHI found that the estrogen-progestin combination had an increased risk for breast cancer. It also promoted heart disease, stroke, blood clots, and urinary incontinence.

The Million Women Study in the UK recruited 1,084,110 UK women aged 50–64 years between 1996 and 2001. They followed up for HRT and cancer incidence and death. The study found that HRT increased the risk of breast cancer. Estrogen-progestin combinations showed a greater risk than other types of HRT.

In 2020, a group of Danish scientists reviewed 22 published epidemiology studies between 2002 and 2019 from different parts of the world. Because breast cancer takes a long time to develop, it is difficult to estimate cancer risk if the participant has not yet shown signs of full-blown cancer. They used mammographic density as a marker to assess breast cancer risk. They found that HRT, estrogen-progestin combination, in particular, consistently increases the risk of breast cancer.

Since HRT causes cancer, why do doctors still promote it?

This is a good question. Let me explain.

To develop a new drug, it must go through 3 phases of clinical trials. Each phase ranges from 3 months to 2 years. With such a short study period, cancer risks are not detected. Long-term studies may observe the development of cancer. Thus, all estrogen-like drugs are safe during the short-term clinical trial period.

The safety data of estrogen are based on short-term clinical trials

Can drug companies do a long-term study to confirm drug safety before marketing it? Maybe not. The reason is that it will take too long to develop a drug. Also, the drug patent protection period is only 20 years. If a drug takes more than 20 years to develop, its patent would expire, and the drug company may bankrupt. Thus, under current regulation, only a short-term clinical trial is possible.

After long-term use, many patients developed cancer. This led university scientists to conduct longer-term studies. In the past 20 years, many studies linked HRT to breast cancer. These findings are published in scientific journals, not targeting laypeople. Thus, many people may not know the cancer risk of HRT. Information about HRT risk is on, WebMD, and the FDA webpages. It is important that you learn it before making a decision that might lead to cancer later in life.

Are Bioidentical Hormones Safer?

The answer is “No.” They are not.

According to the Food and Drug Administration (FDA), American Cancer Society, and the Mayo Clinical doctors, the hormones marketed as “bioidentical” and “natural” aren’t safer than hormones used in traditional hormone therapy, and there’s no evidence that they’re any more effective.

Bioidentical hormones have an equal cancer risk as regular hormones
How to identify false information on estrogen safety?
There are plenty of false information about safety of estrogen.
Estrogen has been well documented to promote cancer by tens of thousands of scientific reports.
But, there is no shortage of information saying a certain type of estrogen is safe.
For example, this report says that "using vaginal estrogen not linked to high breast cancer risk."
Is it true?
Let us look at how many years the study took. The study was from 1993 to 1998. It is a relatively long clinical study for other diseases, but it is too short to test safety for cancer. Thus, the conclusion is false because one may not get cancer in 5 years.
In fact, all estrogen or estrogen derivative drugs, even the ingested forms, have safety studies to back them up. They are all tested safe in both animals and humans. If they do not have safety studies, these drugs cannot be sold.
The concern is that all the clinical studies are based on short-term data. What happens after taking these drugs for a longer term?
To cause cancer, it will require time. You cannot get cancer in a short a few years. It may require many more years of development.
Therefore, if a safety conclusion is based on a short-term data, it is likely false information.
After a long-term use of estrogen, many women get breast, ovarian, and/or uterine cancers, especially the estrogen receptor sensitive breast cancer. You can find this out by just asking cancer survivors.
At this time there are more than 3.8 million breast cancer survivors in the United States. Many may be in your family or neighborhood.
Therefore, we need to be cautious when we see a news report about a certain type of estrogen is safe. We need to check it out to see if it is false information.
About the safety of any treatment product, it is important to identify false information and make a well informed decision.


Is There a Safer Alternative to HRT?

The answer is “Yes.” This is why we developed NeuEve. It provides a natural option for women seeking a safer HRT alternative.

One of the most common menopausal symptoms is vaginal dryness. NeuEve uses a natural approach to relieve it.

For example, when a person suffers from dehydration, there is no needed to take drugs. Drinking water can relieve it. Likewise, vaginal dryness is local tissue dehydration. You can relieve it without using drugs. NeuEve can relieve it, like Chapstick for dried lips. This article explains how it works.

Dehydration: Effective Home Remedies


Disclaimer: This article is for information purposes only. It is about natural products, nutrients, and/or methods for managing menopause-related discomforts (not diseases). It is not medical advice for the treatment of any diseases.


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Dr. Renjie Chang

About the Author

Dr. Renjie Chang's medical and pharmaceutical experience:
- OB-GYN in the Peking Union Hospital in China
- a faculty member of OB-GYN at University of Oklahoma Health Sciences Center
- drug developer at the Abbott Laboratories in Chicago
- Founder of Lavax Inc, where she developed an innovative vaginal microbicide for preventing sexually transmitted disease with grants from NIH and Gates Foundation
- Founder of NeuEve, an all-natural women's health company