HPV vaccine
If Britain were to introduce testing for HPV, the current regime of all women under 49 taking a smear test every three years could be abandoned, and doctors would only focus on those with HPV. Photograph: Voisin/Phanie/Rex Features
The more I investigate the different ways to prevent cervical cancer, the better I understand why the general public – and those who've been sending me their feedback – are confused about the disease. We've seen how HPV (human papilloma virus) vaccination can be affected
by costs, the diseases it would prevent and the culture where it is adopted.
We've also seen that the age women begin cervical screening depends on the in which country they live. But there's also the question of the technology used to screen women.
The science is constantly improving, but is it sensible to adapt screening programmes every time a new method comes out?
The UK is a good example. Several experts I've spoken to consider the NHS cervical screening programme to be one of the best in the world. Some have said it may have
prevented an epidemic. But they also say HPV testing (which is still rarely used on British territory) should become the primary screening method in the near future. Does this mean we should go for a radical change now?
In line with the majority of EU countries the UK currently uses liquid-based cytology
(LBC). This consists in putting a sample of cells from the surface of the cervix into a pot of liquid. The sample is examined under a microscope and the woman may be sent for
colposcopy if any abnormalities are found. LBC preserves cells better than the older method,
the Pap smear. But armed with a deeper understanding of the virus that causes most cervical cancer cases, scientists have developed
HPV testing, a more sensitive screening method.
According to Professor Peter Sasieni from Cancer Research UK (CRUK), it looks for the DNA of the human papillomavirus, picking up many more strains than cytology would. If the test spots an infection, women could then be screened with cytology. Another advantage is that HPV test is simple enough to do in almost any laboratory, whereas cytology requires a subjective analysis by a properly trained technician.
Nevertheless, Sasieni believes HPV testing won't become the main cervical screening method in the UK for another 10 years. Why not before, you wonder? It "would cause chaos", he told me. It would require an investment that the ongoing economic situation might not allow, putting at risk the jobs of a large, skilled workforce. And, as
CRUK's blog reported
last year, he has said there would be no going back if things didn't work out.
What are other nations doing? The Netherlands is the first country with a well-organised cytology-based programme that is considering switching. For countries that are starting from scratch, testing for DNA is best – as Mexico and Turkey are doing. It seems countries that don't even have a current programme may soon be in a better position than the UK.
Introducing both the HPV vaccine and HPV testing will also change how frequently women have to be screened. In England, screening is offered every three years for those aged 25-49 and then every five years until they're 64 - in common with
13 other EU member states. This seems sensible:
a large European study shows that screening every year prevents 93% of
squamous cell carcinoma, but screening every third year still prevents 91% of the cases at much lower costs. With the vaccine and the new screening method, this would change - women would need less frequent screening if found not to be infected, and more cancers would be prevented.
The problem with HPV testing, Sasieni told me, is that in places like Scotland where screening starts at the age of 20, "you would have probably 40% of women testing positive". Being told you have a viral infection is potentially more worrying than an abnormal smear. "By the age of 30 it becomes less common because the immune system has got rid of the infection," said Sasieni.
That appears to be the downside of HPV testing: a higher rate of false-positives.
Once again, the way patients now demand access to tests urges us to understand the wider concepts of preventive medicine. As we saw with the example of
screening age, the more we test, the more harm we might do.
I discussed this with Dr Armando Brito de Sá, a professor of general practice at the
Medical School of Lisbon University. He describes overtesting as a direct breach of "primum non nocere", an ethical principle taught in medical schools which means "first, do no harm". There is a "general and wrong idea that the more exams we do, the better health we have."
Dr de Sá, a practising GP, also explained that once you tell patients the facts they understand that being screened privately at high costs could be more harmful than attending less frequent smear tests under a national programme.
The main aim of my research project has been to track what the scientific evidence says, and find out if it matches policy. A country's budget is a finite sum, so we tend to point the finger at the holders of the purse strings when we can't get access to the treatments we want. I had access to "opportunistic" screening back home in Portugal that is unavailable to women on the NHS over here, but my research has made me realise that "first, do no harm" is probably a more sensible option – and investing in new screening methods like the HPV test is definitely the way forward.
Next week, I'll be looking at data from Africa, where access to screening is limited. Do you know any good examples of cervical cancer prevention in the developing world?
Débora Miranda is a science journalism MA student at City University London and is investigating these questions for her final project. All her source material is posted on her website
cancer-screening.net. She can be contacted via email on
cancerscreeningproject@gmail.com and on Twitter
@debmir