What are the long term effects of HRT?
Publication Date:04/03/2008
Most of the health risks associated with taking hormone replacement therapy (HRT) go back to normal within three years of a woman stopping it, a new study shows. But the risk of getting cancer may increase very slightly. Researchers aren't sure why this is.
What do we know already?
HRT is used to treat troublesome symptoms of the menopause, like hot flushes and mood swings. The hormones in HRT replace those that women's bodies stop making at the menopause. Most women take combined HRT, which contains the hormones oestrogen and progestogen.
However, a big study published six years ago showed that women taking combined HRT were slightly more likely to get breast cancer, and to have blood clots, heart attacks or strokes.
The study ran for five years. Since then, researchers have continued to check the health of the women who were in the study, to see how long the effects of HRT lasted.
HRT can also protect women from thinning bones (osteoporosis), which increases the risk of fractures. But because of the risks associated with HRT, doctors nowadays only prescribe it for menopausal symptoms, not usually as a treatment to prevent thinning bones.
What does the new study say?
The new study looked at what happened to the women during the two to three years after they stopped taking combined HRT. Half the women in the original study took HRT and half took a dummy treatment (placebo).
The study found that most of the long-term risks of taking HRT wore off during this time. For the women who'd taken and then discontinued HRT, the risk of having a blood clot, heart attack or stroke or breast cancer was no longer higher than in the women who'd taken the dummy treatment.
The extra benefit which HRT has for bones had also disappeared. Among women who had taken HRT, the risk of fracture went back up to the risk of the women who'd taken the dummy treatment.
However, among women who had stopped taking HRT, their risk of having any type of cancer got slightly higher. In the two to three years since they'd stopped taking the pills, 16 in 1,000 women who'd taken HRT in the original study had any type of cancer, compared to 13 in 1,000 women who'd taken the dummy treatment.
Tell me more about the study's findings
The main, lasting difference between women who'd taken HRT and women who'd taken the dummy treatment was in the numbers of women getting any types of cancer. Breast cancer didn't account for the increased risk of cancer. This increased risk was down to other types of cancer, including lung cancer. This was a surprise. Researchers haven't looked much at how HRT affects the risk of other types of cancer.
Where does the study come from?
The study was carried out by researchers from several universities in the US, including the Universities of North Carolina, Iowa, Texas and Cincinnati, and Harvard Medical School in Boston. It was published in the Journal of the American Medical Association.
How reliable are the findings?
This was a very big study, which included 16,608 women. The first part of the study was a randomised controlled trial, which is a very reliable type of study. It means that half the people in a group get the treatment, while the other half get a dummy treatment. None of the people taking the tablets know which type they have.
The results from the second part of the study, following the women after they'd stopped taking the treatments, gives us some useful information. However, because it is no longer a randomised controlled trial, it is slightly less reliable.
It would be useful to see what happened to these women in future years, to see whether the increase in cancer stayed higher.
What does this mean for me?
If you've taken HRT in the past, this study is mostly good news. It shows that most of the risks of HRT that we already know about, such as heart attacks, strokes and breast cancer, go back to normal within a couple of years of stopping.
It's hard to know what to make of the increased risk of cancers, especially lung cancer. The main cause of lung cancer is smoking tobacco. We don't know why it should be more common in women who took HRT. However, there were only 48 cases of lung cancer among all of the 16,608 women in the study, so it's possible the differences could be down to chance. The chances of getting lung cancer, for women who don't smoke, are very small, whether they take HRT or not.
The women in the study were mostly quite a bit older than women taking HRT in the UK. Some of them had passed the menopause five to ten years previously. So we're not sure how relevant these findings are for women who are taking HRT for menopausal symptoms within a year or two of the menopause.
What should I do now?
If you've taken HRT in the past, there's no need to take any action as a result of this study. It's a good idea to continue to go for breast cancer screening, as this can pick up early signs of breast cancer. If you have any symptoms that worry you, see a doctor to get them checked out.
If you are considering taking HRT for symptoms of the menopause, this study gives you some more information to think about. You will need to weigh up the benefits and risks of taking HRT with your doctor. Advice for doctors is that women should take the lowest dose that works for them, for the shortest amount of time.
From:
Heiss G, Wallace R, et al. Health Risks and Benefits 3 Years After Stopping Randomized Treatment with Estrogen and Progestin. Journal of the American Medical Association. 2008; 299: 1036-1045.
To find out more, see our information on the menopause.
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© BMJ Publishing Group Limited ("BMJ Group") 2007. All rights reserved
This information does not replace medical advice. If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.
