Cancer Research UK : HRT and cancer

HRT and cancer

Your risk of cancer is influenced by the genes you inherit from your parents

High levels of our own natural hormones can increase our risk of cancer. But some medical treatments can also increase our hormone levels, including hormone replacement therapy (HRT) and the contraceptive Pill.

This page will talk about HRT, how it affects your cancer risk, and how you can weigh up the risks.

What is hormone replacement therapy (HRT)?

After menopause, a woman’s ovaries stop producing the hormone oestrogen. As a result, she may experience menopausal symptoms including hot flashes and mood swings.

Hormone replacement therapy, or HRT, treats these symptoms by boosting the body with more female sex hormones. There are three types of HRT:

Oestrogen-only HRT, which consists only of oestrogen
Tibolone HRT, which consists of a synthetic form of oestrogen
Combined HRT, which consists of oestrogen and progestagen, another female sex hormone

HRT and cancer

In a study of one million women, Cancer Research UK scientists have shown that different types of HRT can increase the risk of different cancers.

Breast cancer. All types of HRT increase the risk of breast cancer but combined HRT does so by much more than other types. Women using combined HRT have double the risk of breast cancer compared to non-users. And if they use HRT for over 10 years, their risks are even higher.

Researchers estimate that over the last decade, HRT use has caused about 20,000 breast cancer cases in the UK. 15,000 of these were caused by combined HRT.

Other cancers. However, oestrogen-only HRT and tibolone can increase the risk of womb cancer, and possibly ovarian cancer. A woman’s risk of womb cancer doubles if she takes these types of HRT for 5 years. Combined HRT has no effect on either of these cancers and may even reduce the risk of womb cancer.

But because breast cancer is more common than womb cancer, combined HRT poses a greater overall cancer risk than other types.

Other effects. HRT has other positive and negative side effects. It can lead to abnormal breast screening results and increase the risk of stroke and blood clot on the lung. But it also reduces the risk of bowel cancer and hip fractures.

Should I take HRT?

HRT is still an effective short-term treatment for menopausal symptoms. Using HRT for a few years doesn’t greatly increase your risk. But the longer you stay on HRT, the higher your risk becomes.

Stopping HRT treatment reduces your risk, which will return to normal by 5 years after stopping.

If you are considering starting or stopping HRT, or using it for a long time, you should consider the risks involved and discuss them with your doctor. The issues are different for every woman. The fact that HRT increases the risk of breast cancer may be more important if you have a history of breast cancer in your family.

Your doctor will be able help you weight up the pros and cons of different types of HRT and make the right choice based on your own circumstances.