Does hormone replacement therapy increase cancer risk?
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• Yes, evidence shows that hormone replacement therapy (HRT) can increase risk of breast, ovarian and endometrial (womb) cancers
• But it’s important to remember that the increased risk is small
• For some, the benefits of taking HRT may outweigh the risks, so talk to your GP about the options
What is HRT?
Hormones have an important role in our bodies. They play a role in controlling things like growth, fertility and our mood.
After the menopause, the ovaries stop producing the female sex hormone oestrogen. So, people may experience menopausal symptoms, like hot flashes and mood changes. For some, these symptoms are very uncomfortable, and HRT can treat them by boosting the levels of female sex hormones in the body.
There are many types of HRT and studies have shown that they can increase the risk of different cancers.
Does HRT increase the risk of breast cancer?
The risk of breast cancer increases for postmenopausal women using any type of HRT. But it is biggest for those using combined HRT, which has the hormones oestrogen and progestogen.
Risk is also higher in those who use HRT for more than 5 years. For these people, the risk remains increased for at least 10 years after they stop using it.
Does HRT increase the risk of endometrial (womb) cancer?
The risk of womb cancer differs depending on the type of HRT.
Oestrogen-only HRT increases the risk of womb cancer. The longer this type of HRT is used, the larger the risk. So, 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. Adding the hormone progestogen can reduce womb cancer risk for those taking HRT. But combined treatment causes the greatest increase in risk of breast cancer. So, it’s important to talk to your doctor about the benefits and risks of HRT for you.
Tibolone, another medication that can help with uncomfortable menopausal symptoms, has also been found to increase the risk of womb cancer.
Does HRT increase the risk of ovarian cancer?
Using oestrogen-only or combined HRT increases risk of ovarian cancer. But when HRT is stopped, risk starts to go back down over time.
It’s not yet clear if there’s any link between ovarian cancer and tibolone.
Should I take HRT?
Risk of cancer with HRT depends on many factors. This includes the type of HRT, when people start taking it, how long they take it for, their age and underlying health.
The balance of risks and benefits is different for each person. So, talk to your GP about what option might be best for you. They should help you decide according to your needs for treatment. There are other things that affect cancer risk more strongly. For example, you can reduce your cancer risk by keeping a healthy weight, not drinking alcohol and stopping smoking.
There are different types of HRT. Your GP can give you advice to help you chose which type might work best for you.
The two main types of HRT are:
• Oestrogen-only HRT, which is only oestrogen, a female sex hormone
• Combined HRT, which consists of oestrogen, and progestogen, another female sex hormone
Combined HRT can be given in two ways:
• Cyclical (or sequential)
Oestrogen is taken daily but progestogen is given in monthly or three-monthly doses
Both oestrogen and progestogen are taken together every day HRT can be taken in different ways, including as tablets, patches or gels.
There are other forms of HRT which are less commonly prescribed. These can include a medication called tibolone. Tibolone is a man-made hormone that has effects like oestrogen, progestogen and testosterone, a male sex hormone.
You can find out more here on the NHS website.
Beral, V. Breast cancer and hormone-replacement therapy in the Million Women Study. Lancet (London, England) 362, 419–427 (2003). https://www.ncbi.nlm.nih.gov/pubmed/12927427
Beral, V., Bull, D. & Reeves, G. Endometrial cancer and hormone-replacement therapy in the Million Women Study. Lancet (London, England) 365, 1543–1551 (2005). https://www.ncbi.nlm.nih.gov/pubmed/15866308
Beral, V., Bull, D., Green, J. & Reeves, G. Ovarian cancer and hormone replacement therapy in the Million Women Study. Lancet (London, England) 369, 1703–1710 (2007). https://www.ncbi.nlm.nih.gov/pubmed/17512855
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. 91, (2007).