HRT, the Pill and cancer risk

In recent years, there has been a concern raised about the taking of hormone replacement therapy (HRT) – to help treat menopause symptoms – and the potential increased risk of certain cancers. Here, we try to explain what exactly that risk is.

On this page:

> What is the menopause?
> Hormone replacement therapy
> Cancer treatments and the menopause
> HRT and cancer
> Bowel cancer
> Breast cancer
> Womb cancer
> Ovarian cancer
> The Pill (hormonal contraception)

What is the menopause?

Menopause happens when the ovaries stop producing eggs and the levels of the hormones oestrogen, progesterone and testosterone fall to undetectable levels within the body.

Most women will experience some symptoms of menopause, and these can range from relatively mild to those that have a significant impact upon a woman’s life.

Symptoms typically include night sweats, hot flushes, low mood and anxiety, and problems with memory and concentration (although there are upwards of 30 different symptoms). They start before the onset of menopause (a stage known as the perimenopause), although they usually start after a woman’s last period and, on average, continue for approximately four years.

Early menopause occurs before the age of 45, while the majority of women experience it between 45 and 55 years or age.

If you are experiencing any of the symptoms of menopause, it’s important that you seek advice from your GP, or a qualified health care professional, about your symptoms, diagnosis and treatment options.

Hormone replacement therapy (HRT)

Because menopause results in long-term hormone deficiency, replacing these hormones can effectively alleviate some of the symptoms. HRT works by increasing the levels of oestrogen and progesterone in the body and is considered the gold standard when it comes to treating menopause. The therapy primarily contains the hormone oestrogen, while often containing a type of progesterone. Taking oestrogen and progesterone together is known as combined HRT.

There are two types of progesterone. The first is micronised progesterone. This is a form of the hormone that has a molecular structure identical to the one produced by the ovaries (referred to as body-identical oestrogen).

The second is synthetic progesterone. This type is chemically different to the oestrogen produced by the body and, therefore, is often not as well tolerated by those taking it as the micronised version.

Progesterone protects the lining of the uterus and levels of the hormone determine the thickness of the lining. Testosterone might also be prescribed for women experiencing menopause. Deficiency of this hormone can lead to a reduction in quality of life including symptoms such as persistent headaches, memory and cognitive problems, reduced libido, and osteoporosis.

Trans men and women may also decide to use hormone therapy; unfortunately, there is not enough evidence to draw conclusions about how this impacts cancer risk. In the future, our hope is that there is an evidence-base strong enough for WCRF to draw conclusions in this area.

> For further information about HRT and menopause, please see our blog post

Cancer treatments and the menopause

Radiotherapy and chemotherapy can both cause ovaries to stop producing eggs – in some cases this might be temporary, while in others the change is permanent and will bring about menopause.

Those diagnosed with ovarian cancer that requires the removal of their ovaries (an oophorectomy), or another disease or condition that requires this operation, will experience menopause shortly after.

HRT and cancer risk

The evidence-base for whether HRT impacts cancer risk is still growing, and more research is needed to confirm potential associations between HRT and cancer risk – especially for site-specific cancers. The factors that seem to determine cancer risk relate to the following:

  • The type of HRT being taken (oestrogen versus oestrogen and progesterone)
  • How the medication is administered (tablets, skin patch, gel, implants or vaginally)
  • Length of time taken (the longer HRT is taken, the greater the risk)

Overall, HRT has many benefits related to physical and mental health for those taking it. For example, reducing the risk of stroke, heart disease and osteoporosis among those going through the menopause.

The small increased risk of cancer is something to consider and discuss with a health professional when thinking about whether to start treatment. Research undertaken by WCRF demonstrates that not smoking, followed by maintaining a healthy weightkeeping active and eating a healthy diet, are the most effective ways to reduce your cancer risk.

Below is the available evidence related to HRT and site-specific cancer risk.

Bowel (colorectal) cancer

There is some evidence that HRT reduces the risk of bowel cancer. Yet, there is not enough evidence to confirm which type of HRT is associated with this reduced risk, the size of the reduction in risk or how long it lasts for.

Breast cancer

There is evidence that HRT increases the risk of breast cancer. However, it’s important to consider that much of this evidence comes from studies undertaken nearly 20 years ago with women who were taking older types of oral combined HRT.

For example, a study from 2002 found a very small increase in breast cancer risk that was not statistically significant. Currently research shows that there’s no change in breast cancer risk among women who take oestrogen-only HRT.

Meanwhile, women who use combined HRT have a slightly increased risk of the disease, as do those who use HRT for longer periods of time. This increase appears to drop-off after HRT is stopped. Again, this risk is small, especially when compared with other factors.

Among women with a family history of breast cancer, there are inconsistent findings related to how HRT might impact breast cancer risk. Therefore, it’s important that you shared this information with your health professional when making decisions about whether to take HRT.

Womb (endometrial) cancer

There is some evidence that oestrogen-only HRT increases the risk of womb cancer – although, as with breast cancer, much of this research is older.

The evidence relating to combined HRT is less clear. Because of this increased risk, oestrogen-only HRT is usually only prescribed to those who do not have a womb – for example women who have had a hysterectomy.

Ovarian cancer

There is a slight increased risk of ovarian cancer among those who take either oestrogen-only or combined HRT. The size of the increase in risk is small, but it is seen quite quickly (in women who have been taking HRT for less than five years). 

However, once HRT is stopped, the risk appears to rapidly reduce and may return to pre-HRT levels.

Hormonal contraception (such as the Pill)

Research to date suggests all types of hormonal contraception, including the combination (oestrogen and progesterone containing) pill, the progesterone-only pill (known as the mini-pill) and the contraceptive patch (which contains oestrogen and progesterone), increase the risk of breast cancer compared with women who do not use these forms of contraception.

But more research is needed to confirm this, especially the link between the progesterone-only pill and breast cancer, where the evidence is less clear.

There’s also some research suggesting a link between long-term use of combined (oestrogen and progestogen) contraception, such as the combination pill and patch, and a small increased risk of developing cervical cancer. With the combination pill (the evidence is less clear for the progesterone-only mini-pill), the risk of cervical cancer slightly increases when taking the pill, but slowly returns to normal after you stop.

For both breast and cervical cancer, evidence shows that 10 years after you stop taking the combination pill, your risk will be the same as if it had never been taken. This has also been shown for breast cancer risk on women who took the progesterone-only pill.

Evidence shows that the pill offers some protection against some cancers, including reducing the risk of developing ovarian (risk continues to decrease the longer the pill is taken for), womb (for at least 15 years after you stop taking the pill), liver and bowel cancers. This may also be the case for the contraceptive patch. More research is needed to confirm these links.

The increase in cancer risk from using any form of hormonal contraception is very small and, for many women, the benefits may outweigh the risk. However, if you are concerned, it is best to discuss your options with your doctor.

Research undertaken by WCRF demonstrates that not smoking, followed by maintaining a healthy weightkeeping active and eating a healthy diet, are the most effective ways to reduce your cancer risk.



Hormonal contraception