Does hormone replacement therapy (HRT) increase cancer risk?
- Yes, hormone replacement therapy (HRT) can increase the risk of breast, ovarian and womb cancer
- But the increased risk is small
- For some, the benefits of taking HRT may outweigh the risks, so talk to your GP about your options
What is HRT?
HRT is a treatment that can reduce symptoms of the menopause by changing hormone levels in the body. Hormones are chemical messengers. They can affect things like growth, fertility and our mood.
During the menopause, the ovaries start to produce less of the hormone oestrogen. This means some people may experience menopausal symptoms, such as hot flushes and mood changes. For some, these symptoms are very uncomfortable, and HRT can help to reduce them.
Trans men and women may also use hormone therapy. But there isn’t yet enough research about cancer risk associated with this. This webpage only covers menopausal HRT and cancer risk.
Types of HRT
The main types of HRT are:
- Oestrogen-only HRT
- Combined HRT, which includes both oestrogen and progestogen
Some other forms of HRT are less commonly prescribed, such as tibolone (external link). Your GP can give you more information about the different types if you think HRT might help you.
Should I take HRT?
Risk from HRT depends on many different things. This includes the type of HRT, when people start taking it, how long they take it for, age, and general health. And the benefits of taking HRT will vary from person to person too.
Everyone’s different, so talk to your GP about your options.
It’s also important to remember that there are other things that affect cancer risk more than HRT. For example, you can reduce your cancer risk by stopping smoking, keeping a healthy weight, and drinking less alcohol.
Does HRT increase the risk of breast cancer?
Most types of HRT increase the risk of breast cancer. But the risk is higher for those using combined HRT, which uses both oestrogen and progestogen.
Vaginal oestrogens are not linked to an increased risk of breast cancer, whereas tibolone is.
Taking HRT for 1 year or less only slightly increases breast cancer risk. However, the longer you take HRT the greater the risks are, and the longer they last.
The risk of breast cancer due to HRT can also vary from person to person. Things such as what age you are when you first start taking HRT, other medicines you may be taking, and your general health can impact the risk.
People who begin HRT before or soon after the menopause may have a bigger risk than those who start HRT later.
Does HRT increase the risk of ovarian cancer?
Yes, both oestrogen-only and combined HRT slightly increase the risk of ovarian cancer. But when HRT is stopped, the risk starts to go back to what it would have been if HRT wasn’t taken.
It’s not yet clear if there’s any link between ovarian cancer and tibolone.
Does HRT increase the risk of womb (endometrial) cancer?
The risk of womb cancer depends on the type of HRT.
Oestrogen-only HRT increases the risk of womb cancer. The longer this type of HRT is used, the bigger the risk. That’s why oestrogen-only HRT is usually only offered to those who have had their womb removed (a hysterectomy) as they have no risk of womb cancer to begin with.
Combined HRT can reduce womb cancer risk. But combined treatment causes the biggest increase in breast cancer risk. So, it’s important to talk to your doctor about the balance of possible benefits and risks for you.
Similar to oestrogen-only HRT, tibolone also increases the risk of womb cancer.
Beral, V. Breast cancer and hormone-replacement therapy in the Million Women Study. Lancet (London, England) 362, 419–427 (2003).
Brown, K. F. et al. The fraction of cancer attributable to modifiable risk factors in England, Wales, Scotland, Northern Ireland, and the United Kingdom in 2015. Br. J. Cancer 118, 1130–1141 (2018). https://www.nature.com/articles/s41416-018-0029-6
IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Combined Estrogen-Progestogen Contraceptives and Combined Estrogen-Progestogen Menopausal Therapy. 100A (2018).
The Lancet. Type and timing of menopausal hormone therapy and breast cancer risk: individual participant meta-analysis of the worldwide epidemiological evidence. The Lancet (London, England). 394, 10204 p.1159-1168 (2019). https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(19)31709-X/fulltext