The Effect of HRT On Breast Cancer Risk

Hormone Replacement Therapy (HRT) is known to increase breast cancer risk, but is still routinely prescribed to help ease menopausal symptoms.

Here’s why.

In 2002, research showed a link between HRT and increased breast cancer risk, and prescribing practices immediately changed. Nowadays, HRT is typically prescribed for women who meet specific criteria for only 3-5 years, and at significantly lower doses than they were pre-2002.

HRT is still a viable treatment option for menopause, and women can mitigate their risk in a variety of ways.

The Basics of HRT

Photo: Adobe Stock/highwaystarz
Photo: Adobe Stock/highwaystarz

The two types of HRT given to women for menopausal symptoms are estrogen-only (ET) and combination (EPT), which consists of estrogen and progestogen. Estrogen offers the most relief from menopausal symptoms, and is typically only given to women who have had a hysterectomy, as it can increase the risk of uterine cancer. Combination HRT is given to women who still have their uterus, as the progesterone lowers the risk of uterine cancer.

HRT is given to replace lost hormones during menopause, which helps ameliorate its symptoms and helps increase quality of life. Menopause typically occurs in a woman’s late 40s to early 50s, when her ovaries stop producing high levels of the hormones estrogen and progesterone, and her period ceases. Some common symptoms include hot flashes, night sweats, difficulty sleeping, vaginal dryness, weight gain, and changes in libido. Symptoms of menopause can last around four years on average, and can have a significant impact on her life.

For most symptoms of menopause, like hot flashes, night sweats, and osteoporosis, HRT will be given systemically, as a pill, patch, gel, spray, or injection. For symptoms like vaginal dryness that are limited to one area, HRT may be given locally, as a cream, ring, or tablet.

The Million Women Study

Photo: Adobe Stock/RFBSIP
Photo: Adobe Stock/RFBSIP

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The Million Women Study is a sprawling project that has been able to churn out dozens of studies concerning women’s health and risk factors over the past couple decades. In 1996, researchers from the University of Oxford partnered with the NHS Breast Screening Programme to determine the relationship between breast cancer risk and hormone therapies used to help with menopausal symptoms. Participants in the study are women in the UK who were born between 1935 and 1950. and were recruited between 1996 and 2001.

The Million Women Study revealed that women who are using HRT have a doubled risk of getting breast cancer compared to women who don’t use HRT. Using HRT for more than 10 years elevates the risk even further. The risk of endometrial cancer (a type of uterine cancer) and ovarian cancer also increases.

The Million Women Study is ongoing, as researchers continue to delve into other risk factors for women’s health that could be modified or removed, such as smoking, diet, and use of oral contraceptives. They’re are working to identify short-term and long-term effects of specific lifestyle choices to determine a clearer picture of what can influence a woman’s risk of getting different cancers, heart disease, stroke, dementia, and other disorders.

Risks and Benefits

Photo: Adobe Stock/Chinnapong
Photo: Adobe Stock/Chinnapong

The risks of HRT depend on how long the therapy is given, the strength of the dose, and the type of therapy. Current recommendations are to give the lowest effective dose for the shortest amount of time possible.

Combination HRT increases the chance of breast cancer, and causes the highest risk during the first two or three years of treatment. In addition, the chance that the cancer will be found at an advanced stage increases, as the combination HRT creates denser breast tissue, making mammograms more difficult to decipher. Subsequently, the risk of developing breast cancer goes down to pre-HRT levels two to four years after going off of it.

Estrogen-only HRT doesn’t increase the risk of developing breast cancer, according to one study released in 2004 by the WHI (Women’s Health Initiative). However, the Million women study did find an increased risk with estrogen-only HRT when compared to women who had never used any type of HRT. They did find that the risk of breast cancer was much lower than the combination therapy, though. Women who used estrogen-only therapy in their 50s or within ten years of menopause have an even more favorable outcome when compared to the combination users.

Photo: Adobe Stock/Natalie Board
Photo: Adobe Stock/Natalie Board

Both ET and EPT have been linked to an increased risk of stroke, blood clots, and heart disease, and the risk increase in women over 60. They also increase risk of ovarian and uterine cancers, as mentioned above. A study in 2015 found that women who are taking HRT for under 5 years are still at an increased risk of ovarian cancer.

Taking HRT close to the time of menopause offers the lowest risk. The longer the hormones are taken in the years after menopause, the bigger the risk.

HRT is not one-size-fits-all, and each woman’s health history, discomfort levels, and symptoms must be taken into account when prescribing HRT. Quality of life during the years of menopause are important to consider as well.

Photo: Adobe Stock/ Darren Baker
Photo: Adobe Stock/ Darren Baker

On the flip side, HRT might reduce the risk of bowel (colon) cancer and stomach cancer, and other diseases, but more research needs to be done. For postmenopausal women, they can help prevent bone loss, bone fractures, and osteoporosis.

According to Cancer Research UK, using HRT is a small risk factor for cancer when compared to other lifestyle factors like being overweight and smoking. Minimizing HRT could prevent 1,400 cancer cases every year in the UK; a healthy weight could prevent 13,200 cancer cases per year; and being a non-smoker could prevent 22,000 cancer cases per year.

Although HRT is the most effective way to cap menopausal symptoms, there are alternative options. A woman can alter her lifestyle to include more regular exercise as well as a healthy diet, reduce caffeine and alcohol, and cut out smoking. There are also other medications that could help with symptoms, like tibolone, antidepressants, and clondine, which come with their own side effects and are not as effective as HRT.

HRT benefits may outweigh the risks for healthy women who experience moderate to severe menopausal symptoms; are losing bone strength and don’t see results with other treatment; or experienced premature menopause (before age 40) or premature ovarian insufficiency (a loss of normal ovary function) before age 40. Early menopause can increase a woman’s risk of osteoporosis, heart disease, shortened lifespan, Parkinson’s-like symptoms, and anxiety or depression, especially if you’ve had your ovaries removed and haven’t started ET by the age of 45.

As always, talk with your doctor about any concerns you may have about hormone therapy.

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