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Taking certain types of hormone replacement therapy (HRT) can double the risk of developing breast cancer, says a study of more than a million women.

The largest ever study into the link between HRT and breast cancer was conducted by scientists at Cancer Research UK's Epidemiology Unit in Oxford.

The research suggests the single pill moderately increases the risk of breast cancer, but the combined pill doubles the risk.

It estimates HRT, taken by women to relieve the unpleasant symptoms of menopause, may have been responsible for an extra 20,000 cases of the disease in Britain in the last decade.

You put your questions to Dr John Toy, medical director of Cancer Research UK and to women's health expert Dr Marliyn Glenville, in an interactive forum.

Transcript

Sarah Fountain:
Hello and welcome to this BBC News Interactive forum. A study of more than a million women indicates that some hormone replacement therapies can double the risk of breast cancer. The study by Cancer Research UK and the NHS suggests the threat is greatest for women using the combined pill treatment. It's estimated that HRT may be responsible for an extra 20,000 cases of the disease in the past decade.

You've been sending in your questions on this issue and joining me to help answer them are Dr John Toy, medical director, Cancer Research UK, and the women's health expert, Dr Marilyn Glenville, joins me on the telephone from her clinic in Kent.

Welcome to you Dr Toy and to Dr Glenville. Dr Toy, we've had an e-mail from Joan Chantrell, UK: How can a woman decide whether to continue with HRT in the light of the research?

Dr John Toy :
It's going to be a somewhat difficult decision to make and one certainly that the woman herself alone shouldn't try to take. She should do that after spoken to her medical adviser. What this study has done is that it has added to the weight of evidence that we've got globally about HRT. So we know that it can be beneficial. But like all medicines, we know that it can have associated risks. This study shows, in rather more specific detail, some of those risks.

Sarah Fountain:
Do you think it's quite difficult to weigh those risks up though?

Dr John Toy :
It can be yes, because if you take the combined pill, which increases the risk most, then you reduce almost to zero any increased risk of developing cancer of the womb. But if you take the oestrogen only pill which doesn't increase the breast cancer risk so much, then you do increase the risk of cancer of the womb and trading these things off is not an easy business.

Sarah Fountain:
Marilyn, what do you say to somebody who's on HRT, are there alternatives that they can take?

Dr Marilyn Glenville:
There are alternatives and obviously they need to see their GP to talk it through as well. My suggestion would be to ask maybe for a lower dose and take it slowly, not just to panic and stop it straight away because sometimes the symptoms can be worse if it's stopped very suddenly. So my suggestion would be to see their GP and talk it through anyway. There are alternatives and we do know from the medical literature that there are some that do work very well and they've been studied scientifically and then they can be put in along with looking at prevention of osteoporosis and having screenings like bone density scans, so they know where they stand.

Sarah Fountain:
John we've had a question about osteoporosis and the fact is that some people are worried that if they don't take their HRT they're going to be at more risk from osteoporosis. What do you say to people like that?

Dr John Toy :
It's true that those who are at an increased risk of developing osteoporosis will be benefited from taking HRT. But there are other treatments that you can take and indeed there are other lifestyle changes that perhaps can be introduced. So keeping fit and healthy is one thing that a woman can do to help herself directly and then there are non-HRT treatments that you can take which have undoubtedly strong benefits in osteoporosis.

Sarah Fountain:
Marilyn, what would you suggest for somebody who's worried about osteoporosis, doesn't want to continue taking HRT? What alternative therapies would you suggest?

Dr Marilyn Glenville:
Well I definitely agree with Dr Toy to actually then look at lifestyle issues. We know exercise plays an enormous role in prevention of osteoporosis. Also to look at things like calcium intake and all of the other minerals and looking at what they're eating. And to even ask for a bone density scan to find out what their bone density is like and look at their family history risk as well. And also there are excellent medications for osteoporosis if they do find out they've got it and they can use those instead of HRT. So there are ways of treating osteoporosis which don't require HRT.

Sarah Fountain:
Going back to HRT we have an e-mail from Gill Russell, Germany/UK and she asks: What alternatives would there be for HRT for someone like me who had a hysterectomy and have been taking HRT on patches ever since?

Dr Marilyn Glenville:
Well I would go then with looking at the other evidence - that scientists have asked why don't women around the world experience the menopause symptoms in the same way and they don't. And they've looked at certain food substances which are called phyto-oestrogens, which are plant oestrogens naturally found in certain foods like soya, chickpeas, lentils, and one can use those changes in the diet. And also we know that certain vitamins actually help with the hot flushes and there is a herb called black cohosh which has had a good amount of clinical research in placebo-controlled trials and is also on prescription in Germany available for women with hot flushes. So there other choices that women can make but it's also a lifestyle change as well and keeping themselves generally healthy.

Sarah Fountain:
Dr Toy what do you think about these alternative remedies?

Dr John Toy :
It's difficult to know really without looking very carefully at each one of them in detail in just the same way that experts look at potential new medicines to see whether or not they can be licensed for a doctor to prescribe them for their patients. So one hears stories about these herbal medicines that may be anecdotal only but actually may be giving a true picture. Unless we have done the research - the sort of thing that Cancer Research UK is doing of course - then we shall not be really be absolutely certain.

Sarah Fountain:
Now this research from Cancer Research UK took in a study of a million women and you think this is fairly conclusive. You are not trying to scare people, you actually think there is a link.

Dr John Toy :
Yes, this is a very large study. If we think of the women in terms of seconds for a moment and we had one pass in front of us every second, it would be 11� days before all of them had passed by. So when you've got such an enormous population, the confidence that you can have in the results goes up enormously too and so we're very confident of these results. And you're quite right, we don't want to be giving out scare messages to women. We want to have women well informed so that they can take mature decisions as an adult about their life and what they would like to do with it.

Sarah Fountain:
Marilyn, do you think you're going to see more women who are worried about HRT and asking you for alternatives?

Dr Marilyn Glenville:
Yes, I think so possibly. I work both in London and Kent and women do come through the practice, even previously with a history of breast cancer or thrombosis and they can't use HRT and I think nowadays women are better informed. They do take part in their own healthcare along with the practitioner that they're with to make an informed decision, weighing up the risks versus the benefits from their own medical history - is there is breast cancer in the family, is there osteoporosis in the family - and actually then having a plan of action as to what is the best for them, how do they approach it and whether they have certain screenings, such as bone density scans. So they actually know where they stand at the moment and then it's much easier to plan what they need to do and who they need to see.

Sarah Fountain:
John we've had an e-mail just in from Jenny Bird in the UK who asks: Have you had the same findings with HRT patches?

Dr John Toy :
Yes, what this study has done because of its size again, is that it has looked at all the sorts of HRTs that the women have been taking and the doses that they've been taking and all of them are associated with an increased risk but some more than with others. There doesn't however seem to be much difference at all between the way in which you have the HRT given - tablet or a patch, or the doses of the HRT in terms of the oestrogen dose.

Sarah Fountain:
We've had an e-mail from Mary, England who asks: Does the dosage have any impact on the level of risk. I am taking Evorel Conti patch - 50g estradiol but could I take a 25g dose and would that make any difference?

Dr John Toy :
From the evidence of this study, it would seem that dose doesn't have a major difference. What the study seems to show more than anything else I think is that it's the duration of exposure to oestrogen which is the important thing to consider. We know that women who have their periods starting earlier in life and have the menopause late in life, have an increased risk compared with other women who are not like that. So now if in the post-menopausal stage we start to add oestrogen obviously we're exposing the woman to a longer duration of oestrogen and it seems to be that rather the dose per se which is the risk.

Sarah Fountain:
William Mackay, Scotland asks: My wife is on a low dose of oestrogen, has been for about 10 years. Is that a potential problem?

Dr John Toy :
Yes, the longer the woman is on HRT the higher the risk and suddenly by 10 years the risk has gone us quite a bit. So one needs again not to frighten women about what does that really mean because we're talking about relative risks and we need to know absolutely how many extra women would get breast cancer if they took the combination over a decade of time, like this gentleman's wife. And we know that there would be an extra 19 cases in 1,000 women if for 10 years they took the combined preparation.

Sarah Fountain:
Marilyn, I've had an e-mail just in from Joy in the UK who asks: I've recently stopped taking HRT after two years and have been taking black cohosh to combat the return of hot flushes. It seems to be working, but is there anything else that I could take that might help me?

Dr Marilyn Glenville:
Yes, so I would take the black cohosh - and we do know that that one has been clinically studied in terms of the herbs so it can be very helpful. And then at the same time, simple lifestyle practical things - there may be some triggers that actually bring on more hot flushes, for instance, something simple like certain caffeinated drinks or the temperature of a drink or even a glass of red wine - women are very individual. But she may see that there is a pattern to some of them. Stress can also bring them on - if a women gets anxious she might have a hot flush. So it's looking to see whether there's any simple practical things that she can do that will also reduce them quicker than just with the black cohosh. Then with her food, to add the simple things like in, like that would be eaten in the Middle East, like hummus or other countries where they would have lentil soup or use organic soya milk. So she's supplementing her diet with the phyto-oestrogens that are traditionally eaten around the world where the women get minimal hot flushes.

Sarah Fountain:
Marilyn, we've had an e-mail from David Cramond, in Thailand who asks: Over recent years there have been many views on the role of Soya Protein in the natural control of menopausal symptoms and the possibility that Soya Protein can help maintain healthier breast tissues, preventing Cancer. Do you think this is a good thing for women to start taking soya milk to prevent breast cancer and to prevent the menopausal systems?

Dr Marilyn Glenville:
We do know from the epidemiological studies that women, for instance, Japan only get one-sixth the rate of breast cancer that we do but within a few years of moving over the rate can equal it. But I would suggest that it's only done with the diet at the moment until there is more research. So not in terms of phyto-oestrogen supplements but to actually change the diet. We know from the dietary side - putting in things like organic soya milk, chick peas, lentils, those kinds of phyto-oestrogens, can have an protective effect against the breast and also help with the hot flushes.

Sarah Fountain:
Do you think a change in diet is an important thing for menopausal women?

Dr John Toy :
I'm afraid I don't really know. I'm a cancer doctor and it would be out of my range of expertise to comment upon that. So I'm going to bow to the expertise of our other expert.

Sarah Fountain:
We've just received this e-mail from Jeff Hayes who says: Surely the many different HRT drugs have different risks and benefits and shouldn't all be lumped together in this analysis. Now I know you've been specific about combined and oestrogen only so perhaps if you could just explain that to us John and say why you talked about all of them in one bag?

Dr John Toy :
The paper which is in tomorrow's Lancet describes in great detail exactly what's been happening. But of course that's a medical paper for a medical readership and therefore we've tried to put across a message which the lay public is able to understand and then that message itself gets condensed down by the media in sound bites. What we have shown is that in the two major classes of HRT; the oestrogen only and the combination of oestrogen and progesterone, there is an increased risk of developing breast cancer for both classes but it's greater - about four times greater - in the combination than it is in the single. And we've also shown that there are preparations that are rather similar to a preparation that was tested in the trial in America and reported last year that also showed that there was an increase in breast cancer and as well as that, some other adverse events which led the trial to be stopped early because they found that the adverse events outweighed the benefits.

Sarah Fountain:
It's not only menopausal women who take extra oestrogen supplements or HRT. We've had two questions e-mailed in, one from Caroline Monroe, England who asks: What implications do the findings have on HRT in Male-to-Female Transsexual women?

Nicole King, UK: Transsexual people, in particular those transitioning from male to female, take very high doses of HRT for very extended periods of time because of the transition from male to female. Do we know what the findings mean to us?

Dr John Toy :
No, not absolutely, we would just have to extrapolate because we haven't studied it, we can't therefore comment on it. But the first thing to say and this perhaps may surprise many people is that men can get breast cancer because men do have breasts although they're not so developed because they don't have the female hormone. Consequently if you now are in a trans-sexual situation where you're giving additional doses of oestrogen to the male, then the risks will go up as they go up for a normal woman who's not on HRT perhaps. So yes, I would anticipate that there would an increased risk of developing breast cancer in someone who's taking oestrogen - whether they are post-menopausal women as we have shown, or a male in a trans-sexual situation.

Sarah Fountain:
Also lots of women take the pill for contraceptive reasons. Do you findings have any implications for these women?

Dr John Toy :
The pill itself does cause an increased risk of breast cancer as I am sure as I hope and trust that all those who are taking it know. But we're talking about a small increase on a small case. So a small bit of a small bit is a small thing and women who are usually taking the contraceptive pill are at an age pre-menopausally when the general risk of breast cancer is low. What this study of ours that we're talking about today - the million women study - has shown is that if you have taken the pill in the past and now you're taking HRT, there is no added risk between the two that we can discern.

Sarah Fountain:
John, we've had another live e-mail in whilst we've been on air. This one is from N Zin Ali who asks: Is the supplement containing human growth hormone an alternative to HRT medication?

Dr John Toy :
No it's not, they are two different hormones. We've all got within our bodies lots of hormones. It may be one of the reasons that there has been a sense, at any rate amongst some people, that taking HRT hormonal treatment is safe because we have hormones in our body. But this shows of course that every medicine if you take it a non-natural fashion has an associated risk with it.

Sarah Fountain:
Marilyn, lots of people have been e-mailing us asking where we can get the black cohosh medication. Is it an over-counter product?

Dr Marilyn Glenville:
Yes, it is over the counter and they can take it as liquids of capsules, so either is fine. It is just worth, I think, paying a bit more in terms of the supplement because they will get a better quality. The one I use is called black cohosh plus and there just are different makes of them. But the more they pay at the moment for a supplement, the quality is better.

Sarah Fountain:
Marilyn, do you have a website where people can find out more about the alternative therapies that you recommend?

Dr Marilyn Glenville:
I do. It is www.marilynglenville.com. And I've also written a book called New Natural Alternatives to HRT which does go through the different ways of actually controlling the hot flushes naturally.

Sarah Fountain:
Having read today's research, what will you be suggesting to women who come to see you in your clinic who are suffering from menopausal symptoms and have been thinking about going onto HRT?

Dr Marilyn Glenville:
Well my suggestion first of all would be to say well if we can control the symptoms naturally and also to do a bone density scan so they know where they stand straight away then why take something that may give them the risk of breast cancer? Obviously the osteoporosis risk needs to be taken in account but it is one of those things that we can usually prevent. Obviously if it is already happening, then there are good osteoporosis medications. But my view has always been, well let's try the natural side first of all to control these night sweats and hot flushes and if it's good enough well that's wonderful and if it's not then there is always HRT and to use it for a short period of time to get over their symptoms. But I would also say after all, to go for the natural side because the menopause is actually a natural event and let's just look at it as a transition and get rid of these symptoms without risking another disease by taking a drug.

Sarah Fountain:
John, where do we go from here now with the research?

Dr John Toy :
Well the million women study will still be looked at for quite a long time to come. New questions will be posed - one of the questions will be: what can we discern in terms of being able to read the breast screening mammograms that women have when they're on HRT when we know that the breast density increases and being able to read the mammogram isn't as it otherwise would be and so what we are knowing now is news about the risks associated with breast cancer. We don't really need to do any more work in that field at all - I think we've got the answer there. But we now need to look at it in a more global perspective for the benefit of women's health.

Sarah Fountain:
I'm afraid that's all we have time for. My thanks to our guest, Dr John Toy and Dr Marilyn Glenville and to you for your many questions. From me Sarah Fountain and the rest of the News Interactive team here in London, goodbye.