HPV vaccines for cancer prevention
Prof Jack Cuzick - Queen Mary University of London, London, UK
Jack, you’re chairing some sessions here, you’re involved with quite a lot of these. Let me start with HPV vaccination, what’s happening here about improving coverage and, for instance, getting boys vaccinated and making everything happen?
Quite a lot is actually happening now. Vaccination programmes have been very good in a few countries, notably the United Kingdom and Denmark where rates are above 80% of girls getting vaccinated. There is now a push to try to expand that. One of the challenges with the current programme is that you vaccinate a girl at 12 or 13 and of course you’re going to have to wait 20-30 years before you really see the impact on cancer. So there’s a lot of interest in actually extending vaccination out to older women, say 25, even out to 40 or so. A new vaccine has come along which has more types in it, so it is clearly more protective. The current vaccines which are Cervarix and Gardesil have only two types against cervix cancer, type 16 and type 18. But the new one has actually added another five types.
What sort of impact on cervical cancer is this sort of preventive measure likely to make, then? The whole programme of vaccination?
Well, vaccinated girls, if you believe that you’ll get full protection against all the types in the nine valent new vaccine could protect up to 90% of cervix cancers so it will virtually disappear.
What about getting the full coverage that you need to get all of the at risk groups?
A major challenge in vaccination is to actually get good coverage across populations. Where it works best is where it’s offered in schools free and provided for by the government and that’s been the model in the United Kingdom. In Denmark they’ve actually been quite successful in getting girls vaccinated through their paediatricians. But in the rest of the world the vaccine coverage has not been great with the exception of Australia which also has a school-based programme which is doing very, very well.
And what sort of level do you have to have it up to, theoretically?
Well, the more the better. Basically we’d like to see 90% of women vaccinated but we’re seeing in the order of 20-30% in many parts of the world now, including much of Europe. So there’s a long ways to go.
And measures you would take to make that change?
There are a number of things. What clearly works is if you can get a programme that’s actually given in schools so that you actually catch the girls when they’re at school. It’s an easy way to do it but that requires a certain infrastructure and a commitment by the government to provide the vaccine.
Let me ask you about breast cancer prevention. There’s the whole question of breast density has come into it, hasn’t there? How do you do risk assessment for women including breast density?
We have been very interested in this for a long time because of our interest in prevention. One of the key things if you’re going to do chemoprevention is to be able to identify those women at sufficiently high risk that the benefits will really outweigh the side effects. So our classical model, the so-called IBIS or Tyrer-Cuzick model, has been used for a long time now and it’s the best current model for actually assessing who is at high risk. Now there are two additional features that aren’t in that model which will be in the next generation; one is mammographic breast density. This emerges as the single most important factor for assessing risk of breast cancer and we’re now able to show in some of the work that we’ve done recently that it adds substantially to the classic information in the Tyrer-Cuzick model.
Typically what do you think doctors should be doing about incorporating all of these risk factors?
My view is that we should really rethink the breast screening programmes and the breast screening invitations to make them more of a cancer prevention activity. So a woman comes for breast screening, she’s already got some anxiety about breast cancer so it’s a good time to talk about risk. You also get the mammogram which provides, by looking at the density, a major factor for risk. Put that all together, it’s an excellent time to begin to teach women about what their risk is and how they might reduce it.
What are the options, then, for women to prevent breast cancer?
There are a number of things. It’s fairly clear that maintaining physical activity is very important and that’s something that everyone can do. Just keeping physically active and there’s a range of things that you can do – make sure you walk a little bit more, try to walk up stairs, those kinds of things. The other important thing for the general population is to watch weight, that being overweight is a risk factor for post-menopausal breast cancer. Now, the real interest, I think, is what you do for the higher risk women where that’s probably not enough, that’s going to give you maybe a 20-30% reduction. It’s good for the general population but if you’re at high risk you want more. What’s been actually approved in the United States is tamoxifen and raloxifene, these are two selective oestrogen receptor modifiers that have been used quite widely and give you about a 30-40% reduction. More recently there are two trials come out which have actually shown that for post-menopausal women the aromatase inhibitors, either exemestane or anastrozole, are even more effective and produce more like a 60% reduction, so a really quite substantial reduction in risk.
Now, cancer doctors inevitably are going to get consulted to give advice on these matters. How would you summarise what sort of advice they need to be giving to women to avoid breast cancer?
The real challenge now is that we do need to provide more education to doctors because they are not aware of the issues. The primary fact is that breast cancer is still the commonest cancer in women and that you can make a substantial reduction in risk with preventive therapies. This has been done in cardiovascular disease for a long time, nobody thinks twice about taking a statin if their cholesterol is high. We need to do the same in breast cancer by saying if you’re at high risk of breast cancer there are some preventative therapies that you can take. Tamoxifen and raloxifene are the more widely accepted ones now but the newer ones which look to be better are the aromatase inhibitors.