I thought research was presented to peers at conference etc for scrutiny before it was considered for policy.
The trouble with epidemiology and statistics is that it can find link, which this has done. We know that there is a link with breast cancer and HRT. But we do not know what that link is and hard science RCT are needed to find out what that link is and isolate the mechanisms, then something can be done.
We knew there was a link before, and this study shows that link exists (again) and that it may last longer than thought, but it still does not tell us what that link is. There have been a number of studies since the millennium and million women trials looking at different progestogens to see if that could be a cause, and detailed analysis of the numbers has shown that it could be an effect, but we need a lot more of this sort of research before we get any answers.
I don't know why this study got so much attention. They have only said there is a link and have not come up with anything that proves that HRT actually causes BC, and the study does not show that HRT increases the number of deaths from BC.
This study is the result of a joint effort of the Collaborative Group on Hormonal Factors in Breast Cancer, comprising 133 institutions around the world. I reckon they have discussed the study extensively before submitting it for publication, but of course there must be an equal number of scientists and other people trying to understand and possibly challenge their findings (it happened with the WHI trial). If the UK government is considering it for policy, I reckon it's because it's a robust study and the implications are serious for public health policy.
https://www.gov.uk/drug-safety-update/hormone-replacement-therapy-hrt-further-information-on-the-known-increased-risk-of-breast-cancer-with-hrt-and-its-persistence-after-stoppingI don't see any problem in finding links, or associations. They are very useful for seeing the big picture as long as no causality is inferred. Epidemiology studies are about groups of people, not individual patients. No government could exist without it. Statistics is a tool for all scientific studies. No science would survive without it.
There are not enough data from long term use of HRT studies to be analysed and breast cancer takes a long time to develop, but in the meantime, scientists who have a lot of data at their disposal won't just wait for a ‘hard science RCT' until ‘something can be done'. The purposes of Randomised Controlled Trials are not to isolate mechanisms, these are done via molecular studies in vitro and in vivo, usually using model animals. To isolate hormonal mechanisms using humans as objects would be a bit complicated. RCTs are important to provide strong evidence of cause-effect, IF they are well designed and methodologically sound. They also can be flawed.
This is not the purpose of this study, all analyses on risk ratios are welcome, until molecular investigations can find ‘that link'.
What could be a cause and what could be an effect of what? Sorry I can't understand what you mean. Do you mean that ‘detailed analysis' of the use of different progestogens ‘has shown' that ‘it' (breast cancer?) could be an effect? If that's what you mean, yes, and as I said before, scientists work with available data and if ‘this sort of research (that we need a lot more of)' takes a long time to achieve any significant results, scientists can't just wait.
The study aim was not to prove causality. Actually, scientific studies rarely ‘prove' anything beyond doubt, they are usually about evidence that can corroborate hypotheses or about data collection, analysis and interpretation, like this one.
This objection 'the study does not show that HRT increases the number of deaths from BC' keeps being raised by many doctors and ‘experts'. From a purely personal point of view, I would like to know what are my chances of getting breast cancer if I'm on HRT, independently of what comes next. Breast cancer mortality rates depend on many other variables. From the public health point of view, it's very important to know that HRT use can increase the absolute risks of BC (which has been provided by this study) not just during the use of HRT (up to 5 years), but also 15 years after discontinuation (which is a new finding of this study), for the very important reason that the NHS and equivalents around the world are going to pay for those breast cancer treatments, not to mention the obvious implications for individuals.
This study is about numbers (patients, years of HRT use, age, risk ratios), it is not about proving causality, there's a big IF in the Interpretation section:
‘If these associations are largely causal, then for women of average weight in developed countries, 5 years of MHT, starting at age 50 years, would increase breast cancer incidence at ages 50–69 years by about one in every 50 users of oestrogen plus daily progestagen preparations; one in every 70 users of oestrogen plus intermittent progestagen preparations; and one in every 200 users of oestrogen-only preparations. The corresponding excesses from 10 years of MHT would be about twice as great.'
It would be useful if one can separate what has been demonstrated in a 67-page study from 1-page media reports.
It's nice to be able to discuss things deeply and not let emotions and preconceptions get in the way. Science can certainly be flawed but it's still the best tool we have to address these flaws.
Sorry for not multiquoting, it's terribly difficult when there's no such an option, at least I haven't found it.
BeaR.
Author
Topic: Link to Guardian article this morning re increased breast cancer risk on HRT (Read 29265 times)