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Hormone replacement therapy reduces breast cancer risk by 25% in women who have had hysterectomies

Hormone replacement therapy lowers breast cancer risk by 25% for women who have had hysterectomies – but increases the risk by almost as much for anyone who still has a uterus, research shows

  • Researchers looked at postmenopausal women on hormone replacement therapy (HRT) compared to women on placebo
  • Women who had hysterectomies and took HRT had a 25% lower risk of breast cancer than women without a uterus but who took a placebo
  • The risk of breast cancer death was also lower: 53% fewer HRT women died than those on placebos
  • But in women who had not had a hysterectomy, HRT increased breast cancer risk by almost 25%

Hormone replacement therapy (HRT) may lower breast cancer risk for some women, but increase it for others, a new study finds.

Researchers found that women who had their uterus removed and who took HRT were about 25 percent less likely to get cancer than women who received a placebo.

In addition, this same group of women was more than 50 percent less likely to die from breast cancer.

But the University of California Los Angeles Medical Center team also found that women who had their uterus not removed increased their cancer risk by nearly a quarter by taking HRT.

Women who had hysterectomies and received hormone replacement therapy had a 25% lower risk of breast cancer than women without a uterus but with a placebo (file image)

Women who had hysterectomies and received hormone replacement therapy had a 25% lower risk of breast cancer than women without a uterus but with a placebo (file image)

There are two main types of HRT: combination HRT, which contains both estrogen and progesterone, and estrogen-only HRT.

Previous research has found that combination HRT, often used by postmenopausal women to relieve menopausal symptoms, increases breast cancer risk by about 75 percent.

There is also a greater chance for users of combination HRT that the cancer may be found at a more advanced stage.

Scientists think this is because cancer cells often contain hormone receptors.

The risk decreases when it comes to estrogen-only HRT. Only when used for more than 10 years is the prospect of a breast cancer diagnosis raised.

For the study, published in JAMA, the team followed two placebo-controlled randomized clinical trials involving more than 27,000 postmenopausal women.

Women were enrolled in 40 centers across the country from 1993 to 1998 and were followed through December 31, 2017.

In one study, involving more than 16,600 women with a uterus, about 8,500 received two doses of HRT – estrogen and estrogen plus progestin only, which is a synthetic progestin – while about 8,100 received a placebo.

In the second study, researchers look at women who perform hysterectomies, procedures that remove the uterus and ovaries.

About 5,300 received one dose of HRT containing only estrogen and about 5,400 received placebo.

The results showed that women with previous hysterectomy and HRT use were much less likely to develop breast cancer.

There were 238 cases among women without a uterus and taking the medication, compared with 296 receiving a placebo – a difference of 24.3 percent.

In addition, there was a lower breast cancer mortality among women with HRT with 30 deaths compared to 46 deaths, a 53 percent difference.

For comparison, HRT in women with uterus was linked to a statistically significantly higher incidence of breast cancer.

About 23 percent more women on HRT developed breast cancer with 584 cases compared to 447 cases.

However, there was no notable difference in breast cancer mortality between these groups.


Menopause, which often affects women in their late 40s and early 50s, can cause depression, hot flashes, headaches, and night sweats. In the long run, it can also cause bone disease and memory loss.

Hormone replacement therapy (HRT) addresses these symptoms by replacing the female sex hormones – estrogen and progestin – when the body no longer produces them.

But while it can change the lives of many women, studies have shown that there may be an increased risk of breast cancer and heart disease from HRT. As a result, many women no longer accept HRT treatment and some doctors will not prescribe it.

However, the Woman’s Health Concern (WHC) noted that one of the American studies used women in their mid-sixties who were often overweight as test subjects, and these are not representative of women in the UK.

In addition, a 2012 controlled study from Denmark reported that healthy women who used combined HRT for 10 years immediately after menopause had a reduced risk of heart disease and death from heart disease, which is in contradiction with reports from previous studies.

The WHC says HRT is safe, provided it is taken for the right reasons, namely to alleviate menopausal symptoms, and with the minimum effective dose.

Source: WHC