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HRT increases breast cancer riskBupa investigative news - 19 August 2003
Hormone replacement therapy (HRT) is a drug used to help women cope with the unpleasant effects of the menopause, which normally occurs between the ages of 42 and 58 years. It was known that HRT increased the risk of breast cancer, but the Million women study has quantified the risk for oestrogen-only HRT and has shown that use of combined HRT is associated with a higher-than-expected increase in risk. So what does this mean to the thousands of women who take HRT? What were the headlines?With breast cancer being such a key issue, and the study involving such a vast number of women, the research instantly made the front pages of many UK newspapers. Coverage appeared in the majority of mainstream publications, gaining headlines such as, "HRT 'doubles breast cancer risk'", "Millions hit by breast cancer alarm", "HRT can double the risk of breast cancer", "HRT linked to breast cancer" and "HRT found to give early benefits, but risks persist". What is the bigger picture?The study in question is called the Million Women Study and the details were published in The Lancet medical journal. The study was funded by Cancer Research UK, the NHS Breast Screening Programme and the Medical Research Council, and 1,084,110 women in the UK aged between 50 and 64 years old were recruited between 1996 and 2001 through the NHS breast screening programme. Half the women had been using HRT or had done so in the past, and amongst the women there were 9,364 cases of invasive breast cancer and 637 deaths due to breast cancer. The data was analysed by scientists at the Cancer Research UK Epidemiology Unit in Oxford. They discovered that post-menopausal women taking combination HRT were twice as likely as non-users to develop breast cancer. In women taking tibolone, the risk increased by 45 per cent, and for those on oestrogen-only HRT, the risk was 30 per cent greater than for nonusers of HRT. This means that:
The increase in risk starts to become apparent within one to two years of starting either form of HRT and increases the longer it is taken. As soon as HRT is stopped, the risk begins to fall and, after five years, is the same as for women who've never taken the drug. Professor Valerie Beral, director of the Cancer Research UK epidemiology unit, and lead author of the study, said, "We estimate that over the past decade use of HRT by UK women aged 50-64 has resulted in an extra 20,000 breast cancers, oesterogen-progestogen therapy accounting for 15,000 of these." "Combined oestrogen-progestogen HRT is usually prescribed for women who still have a uterus," she explained, "to avoid the increased risk of cancer of the uterus caused by oestrogen-only therapy." "Since our results show a substantially greater increase in breast cancer with combined HRT, women need to weigh the increased risk of breast cancer caused by the addition of progestogen against the lowered risk of uterine cancer. Comparing the risks is by no means simple, and women may well want to discuss options with their doctor," she advised. According to Dr. John Toy, medical director of Cancer Research UK, "Previous reports have indicated that breast cancer risk increases in women taking HRT and this vast new study, the largest ever conducted, has allowed accurate assessment of the size of the effect. On a national scale, with so many women taking HRT, the number of extra cases of breast cancer has been quite large, but the increased risk does start to fall on stopping treatment." He added that, "It would be sensible for a woman to take HRT for only as long as it is necessary to deal with her medical problems, as advised by her doctor. A woman wanting to take HRT for a long time would be extremely wise first to consider carefully the findings of this large study and other relevant research."
What does this mean?Professor Duff, chair of the Committee on Safety of Medicines (CSM), said, "This high quality study is important as it reflects what is actually happening in HRT users in the UK. We have reviewed the study carefully and realise that these findings may present women and their doctors with a dilemma about long-term HRT treatment." "However," he added, "what this study clearly shows is that, in all cases, the additional risk of breast cancer begins to decline when HRT is stopped and by five years reaches the same level as in women who have never taken HRT." Samia al Qadhi, joint chief executive of Breast Cancer Care, said, "Breast Cancer Care welcomes any research that contributes to our understanding of the risk factors linked to breast cancer. These recent findings are very significant as they highlight a specific type of HRT which may increase a woman's risk of getting breast cancer." Delyth Morgan, chief executive of Breakthrough Breast Cancer, described the findings as "very disappointing". She said, "There has been a strong suspicion that HRT is implicated in breast cancer for many years and the results confirm our worst fears." Dr. John Stevenson, from the British Menopause Society, said, "The findings of this new study are in line with findings of previous studies, both observational and randomised clinical trials, that HRT use is associated with a small increase in risk of breast cancer being found." However, he said, "The authors extrapolate their findings as showing that HRT has been responsible for 20,000 additional cases of breast cancer over the past 10 years in women aged 50 to 65 years. But if one looks at the risk of women not getting breast cancer over this period, the use of HRT changes it from 99.3 per cent to 98.9 per cent - a much less alarming (and less sensational) statistic." What's more, he points out that, "In women taking combined HRT for 10 or more years - the group at highest risk for developing breast cancer - then, in absolute terms, the excess risk is still confined to around three-quarters of one per cent of these women. The increased risk for breast cancer from HRT remains much the same as the increased risk from drinking alcohol, and is still less than the increased risk associated with being overweight."
What does this mean to me?The CSM launched new advice for doctors and patients as soon as the research was made public. They advise that for short-term use the benefits outweigh the risks for many women, but that women should be aware of the increased risk for longer-term use. According to Professor Duff from the CSM, "The new findings mean that it is even more important that each decision to start HRT is made on an individual basis, and is reassessed at least annually. Women who are concerned by these new findings should make a routine appointment to discuss these matters with their doctor." Although welcoming the CSM guidance, Delyth Morgan said the "lack of clarity regarding 'short-term' use will leave many women unable to make a truly informed decision. Specific guidance on the different types of HRT is also needed." She added that, "Women want as much support as possible to weigh up the pros and cons of taking HRT or whether to come off it." Samia al Qadhi admitted that women may be worried by the study, especially the widespread news coverage it produced, but was keen to try to allay their fears. "We have daily contact with many people with breast cancer concerns and we are aware that this research may cause anxiety amongst women," she said. "However, HRT use has known benefits and if women are worried about these findings and how they relate to their own HRT use, we recommend they discuss their concerns with their GP in order to make an informed choice. We would also like to highlight that age remains the single most important risk factor for breast cancer," Samia al Qadhi added. Both Breast Cancer Care and Bupa's Dr. Rebecca Small add that the study highlights the importance of breast awareness - of checking your breasts regularly for changes and for regularly attending breast screening. SummaryThe Million Women Study has helped confirm that HRT increases the risk of developing breast cancer. It quantified the risk of breast cancer associated with taking oestrogen-only HRT. It has shown a higher risk than previously thought with the use of combined HRT. It also provided new information about the risk of breast cancer with tibolone. Women who are concerned by their potential risks should discuss their concerns with their GP at their next routine appointment. Women should also remain alert for changes in their breasts both by carrying out self examination and by attending regular breast screening. Links for more information
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