Vaccination and testing for the human papilloma virus could eradicate cervical cancer
(24 September 2009: VIDYYA MEDICAL NEWS SERVICE) -- Cervical cancer could be eradicated within the next 50 years if countries implement national screening programmes based on detection of the human papilloma virus (HPV), which causes the disease, together with vaccination programmes against the virus, according to a cervical cancer screening expert.
Professor Jack Cuzick told Europe's largest cancer congress, ECCO 15 – ESMO 34 , in Berlin today (Thursday 24 September) that while the current HPV vaccines protect against two cancer-causing strains of the HPV virus, soon there would be vaccines available that protect against nine types. If vaccination were to be combined with HPV screening (which is much more sensitive than the currently used Pap smear test), then eventually the cancer would disappear in those countries that had successfully implemented national programmes. However, this would require political will and effort at both national and European level.
"It's important to say up front that the HPV is responsible for all cervix cancer," said Prof Cuzick. "If you can eradicate the virus, the cancer will not appear. So the current vaccine holds the promise of eradicating about 70-75% of cervical cancers (caused by HPV types 16 and 18), and there appears to be some additional cross protection amongst types that are closely related to 16 or 18, in particular 31, 45 and a little bit of 33. There are new vaccines being planned that will vaccinate against nine types. If they are successful, there should be no need to screen women that have been vaccinated at all. That's the long-term future: vaccination and no screening. After about 50 years, we could see cervical cancer disappearing."
As the current HPV vaccine only protects against two of the cancer-causing types, vaccinated women will still require screening for the rest of their lives.
"Women vaccinated above the age of about 16 will need to be regularly screened for the rest of their life, because the vaccine is not effective in women who have already been exposed to the virus. Even for girls vaccinated before this age with the current vaccine, there will be a need for some screening to protect from cancers caused by HPV types not in the vaccine, so screening is here to stay for the foreseeable future. However, we need to change to screening for HPV rather than the Pap smear test, and then it will be possible for the tests to be conducted at longer intervals," said Prof Cuzick, who is the John Snow Professor of Epidemiology and head of department at the Cancer Research UK Centre for Epidemiology, Mathematics and Statistics, Wolfson Institute of Preventive Medicine (London, UK).
The Pap test uses cytology to detect pre-cancerous changes to cells; it relies on subjective assessments by people examining the cells in the smear with a microscope and so is open to human error. Prof Cuzick believes such errors will increase as the proportions of smears with affected cells decline due to increasing numbers of women having been vaccinated. In contrast, the HPV test is almost completely automated, is designed to detect the virus in the smear rather than relying on visual examination, and so is much less likely to be affected by human error.
Prof Cuzick said that countries should be switching to the HPV screening test now. "There's overwhelming evidence that HPV screening is more effective than the Pap smear test, which misses about a third to a half of all high grade lesions. There are now several available commercial HPV tests and most of these tests show a sensitivity (the proportion of true positives correctly identified) in the order of 95% for high grade lesions, whereas cytology is somewhere between 50-70%. So it would really streamline the service because you could test less frequently, and it's also been shown that the protection lasts longer so that screening every five to seven years is probably appropriate."
However, he warned that the European Union and national governments should take the initiative in discussions on implementing screening and vaccination programmes, rather than leaving it to pharmaceutical companies to lead the debate.
"The European Commission and Parliament, together with national governments, could be doing more to promote HPV testing. One of the most useful things the EU could do would be to provide a forum for the dissemination of knowledge about the role of HPV both to doctors and to the general public. It could sponsor a major symposium to discuss HPV testing, vaccination and the best strategies for implementing programmes in member countries.
"There's been a lot of concern, particularly with the vaccine, that dissemination of information about HPV has come mainly from the drug companies, and people are, not surprisingly, a little sceptical of pharmaceutical-based education programmes. So if the EU was to take this up without pharmaceutical support, I think it would be very appropriate and it would provide a forum that would be extremely legitimate."
Although current HPV tests are more expensive than cytology tests, Prof Cuzick said the price would go down as the volume of tests increased. In addition, the fact that it's more accurate and women could be screened at longer intervals meant that switching to HPV testing could save governments money in the long term.
"For younger women we think HPV testing should happen every five years starting at age 25-30; by the time they're 50, if they've been negative, they could probably be screened every eight years. So there's a lot to be gained, both in terms of better protection and less frequent screening, which will save time and money. If women can go less often and get more protection it makes a lot of sense."
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