HRT, the Pill and cancer risk

Do HRT and hormonal contraceptives increase the risk of cancer?

Hormone replacement therapy (HRT)

HRT is taken by women going through the menopause to help reduce symptoms, such as hot flushes, night sweats and mood changes. It works by increasing the amount of oestrogen, which naturally drops during the menopause, in the body.

There is strong evidence that taking HRT increases the risk of breast, womb and ovarian cancers. However, this increase is only slight – fewer than 2,000 cases of cancer are thought to be preventable in the UK if everyone avoided taking HRT, compared with nearly 25,000 cases that could be prevented by maintaining a healthy weight.

A woman’s exact risk is dependent on the type of HRT being taken, how long it is taken for and how strong the dose is.

HRT does have benefits for women. It can improve quality of life by relieving many of the symptoms of menopause. There is also evidence that it can reduce a woman’s risk of developing bowel cancer and osteoporosis (thin or weak bones).

It is best to discuss whether to start or stop using HRT with your doctor, who will be able to tell you what options are available to you. For some women, the benefits may outweigh the risks. However, to minimise the risk of breast cancer, it is preferable to use the lowest dose of HRT necessary to relieve your symptoms for the shortest possible time.  

Not smoking, followed by maintaining a healthy weight, keeping active and eating a healthy diet, are the most effective ways to reduce your cancer risk. 

HRT does affect different cancers in different ways, though the overall increased risk is small.

Breast cancer

Studies have shown that taking combined HRT (which contains the hormones oestrogen and progesterone) increases the risk of breast cancer. The evidence about oestrogen-only HRT is less clear – it may also increase risk, but to a lesser extent than with combined HRT.

With combined HRT, the risk of developing breast cancer increases slightly the longer you take HRT, but decreases gradually once you stop. Five years after stopping HRT, the risk of developing breast cancer will be the same as if it had never been taken. The evidence is less clear for oestrogen-only HRT.

Naturally occurring oestrogen and progesterone are thought to affect the growth of some breast cancers – having higher levels of these hormones from taking HRT might explain why it increases the risk of breast cancer, but we don’t yet know for sure.

Womb (endometrial) cancer

There is strong evidence that oestrogen-only HRT increases the risk of womb cancer. The evidence relating to combined HRT is less clear: the increase in womb cancer risk seems to be smaller in women using combined HRT than oestrogen-only HRT. It is also possible that, with the correct dose of progesterone within combined HRT, there is no effect on risk, but this is still to be shown in the evidence.

Ovarian cancer

Evidence has shown an increase in risk of ovarian cancer from taking both combined and oestrogen-only 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 stops being taken, the risk does start to reduce.

Bowel (colorectal) cancer

There is some evidence that HRT may reduce the risk of bowel cancer, but as yet there is insufficient evidence to confirm which type of HRT is most beneficial, the size of the reduction in risk or how long the benefit lasts for. More research is needed to confirm these.

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 is 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 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 the pill offers some protection against some cancers, by 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. 

Not smoking, followed by maintaining a healthy weightkeeping active and eating a healthy diet, are the most effective ways to reduce your cancer risk. 


Sources
HRT
Hormonal contraception