This method could lead to a transformation of the screening programmes for cervical cancer offered to Danish women today.
What is the most effective way of detecting precancerous cervical cells? Looking at a cell sample – a smear – under a microscope, like we do today in Denmark and many other countries? Or screening the cell sample for HPV (Human Papillomavirus)?
This is the key question posed in an article recently published by Danish researchers in the scientific journal Clinical Epidemiology.
And the article’s conclusion is clear, explains Louise T. Thomsen from the Danish Cancer Society:
‘With HPV screening, we can detect up to 50% more cases of severe precancerous cervical cell changes than with the classic microscopy-based technique, giving a strong indication that we should switch to HPV screening in Denmark,’ says Louise Thomsen, postdoc in public health and first author of the scientific article.
The study behind the article was funded by the Lundbeck Foundation, Region Danmark and the MERMAID Project, and the researchers looked at analyses of cell samples taken from around 28,000 Danish women, aged between 30 and 59.
The samples were taken at Vejle Hospital in 2017 and 2018 and were then either screened for HPV or analysed using the classic microscopy-based method.
Comparing the results from the two groups, researchers were able to see that HPV screening is significantly more effective than classic microscopy-based analysis when it comes to detecting precancerous cervical cells. Louise Thomsen explains:
‘For every 1,000 women examined using HPV screening, we found 14 cases of these severe precancerous cell changes. By comparison, we found nine cases per 1,000 women using the classic microscopy-based method.’
HPV is the true villain
Based on this study of the efficacy of the two screening methods – traditional microscopy and HPV screening – the Danish Health Authority is considering introducing a new procedure for cervical cancer screening in Denmark.
If they decide to replace the current microscopy-based method with HPV screening, Denmark will join the number of other countries already following this path, including the Netherlands, Italy and New Zealand.
Louise Thomsen, from the Danish Cancer Society, explains that Norway and Sweden – two of the countries whose health systems are most comparable with the Danish system – are currently in the process of introducing screening using HPV tests:
‘Our study shows that it makes perfect sense to screen for HPV when looking for precancerous cervical cells. In fact, HPV is the cause of almost all cases of cervical cancer – particularly HPV16 and HPV18, which account for 70% of cases.’
Risk of unnecessary concern
However, before we roll out HPV screening to replace traditional microscopy, we need to give careful consideration to a potential side effect of this screening technology.
As Louise Thomsen says, HPV screening is so effective that there is a risk that a large number of women will be called in for further examination by a gynaecologist due to a suspicion of precancerous cervical cell changes when there’s actually nothing wrong with them:
‘And we have to reduce this risk as much as possible, because it will be a burden on the health system’s resources and could cause unnecessary concern in the women.’
Around 375 Danish women are diagnosed with cervical cancer every year. This number is expected to decline over the coming decades due to the fact that systematic HPV vaccination has been added to the national childhood immunisation programme.
There are more than 100 different types of HPV, around 15 of which may be carcinogenic.
Danish women between the ages of 23 and 49 are offered examination of a cell sample – a so-called smear – once every three years. Women between 50 and 64 are offered the same examination once every five years. In 60–64-year-olds, HPV screening is used.
If there is a suspicion of precancerous cervical cells, the woman will be referred for a colposcopy, or, in some cases, a new smear will be taken. If, when a colposcopy is performed, severe precancerous changes are detected in the tissue samples taken, the women will undergo a cervical cone biopsy.
The Danish study was conducted by researchers from the Danish Cancer Society, Rigshospitalet, University of Copenhagen, Vejle Hospital and the University of Southern Denmark.
Foreign studies have previously shown that HPV screening detects more cases of precancerous cervical cell changes than a microscopy-based method.
80% of all women will have an HPV infection at some time during their lives. Most of these infections will disappear on their own, without doing any harm.