Screening currently involves looking at cells down a microscope
Cervical screening is never far from the headlines – just look at this week’s stories on possible ways of increasing the number of women taking part. And recently there’s been much debate about the ages when women are screened.
But is it all about age? Or are there other areas where new evidence points to potential changes to the programme?
To mark cervical screening awareness week, in this post we’ll explore the latest evidence about cervical screening – including the evidence about screening age – and how we think the programme could be improved to help save even more lives in future.
Science isn’t static
It’s not surprising that debates about issues like screening age keep cropping up. The very nature of science and medicine means that researchers constantly publish new evidence and data that could improve things such as screening programmes.
So it’s important that the Government keeps abreast of this evidence, so that screening can do what it’s designed to – prevent more cancers and save more lives.
In the field of cancer screening, hundreds of scientific papers are published every month, and we keep on top of the lot, distilling them down to what we think is really useful.
So what’s the evidence on age? And does it match up with how the current programme works?
20 or 25?
In England, the cervical screening programme is offered to women after their 25th birthday.
But after the tragic death of 19 year old Sophie Jones in March, a huge online petition reached the Government, asking them to offer screening to women under 25.
This is clearly a very sad and emotive subject, but based on the balance of evidence at the moment we think that inviting healthy women under 25 for cervical screening would be likely to do more overall harm than good.
But first, it’s vital to clear up one very important thing. If women have symptoms, at any age, they should tell their doctor, even if they’ve recently been for screening.
Doctors can then offer appropriate diagnostic tests (which aren’t the same as cervical screening), no matter how old the patient. It’s important that women get these diagnostic tests promptly, as well as any subsequent treatment they need.
But cervical screening isn’t designed to spot women who already have cancer (although it occasionally does) – instead it aims to find subtle changes to the cells lining the cervix that could go on to become cancer in the future.
These abnormal cells can be removed, preventing cervical cancer from developing in the first place.
Here’s the important bit. In younger women, these abnormal cell changes develop more often but, crucially, are much more likely to clear up by themselves. Research has shown that, compared to older women:
- Younger women are more likely to receive an abnormal test result
- Cell changes found in younger women are less likely to develop into cancer
- Younger women are therefore more likely to have unnecessary further investigations and treatments
How does this translate into actual numbers? A recent study compared data from England – where screening starts at 25 – with data from Wales, during a period when screening started at age 20. This allowed researchers to estimate that, for every 100,000 women invited for screening from age 20 rather than 25, the programme would:
- Prevent between 3 and 9 cancers
- Lead to 8,000 extra unnecessary referrals for further tests (colposcopy)
- Lead to 3,000 extra women receiving unnecessary treatment for abnormal cell changes
This treatment can lead to side effects – including severe bleeding – and it could also raise the risk of premature birth in later pregnancies.
Decisions on screening programmes are based on recommendations from the UK National Screening Committee, which brings together leading experts to review all the evidence.
They then consult with the public to make recommendations. They last looked at the cervical screening age range in 2012, and decided to keep the lower age limit at 25. We agree with this assessment.
What about older women?
It’s not just the lower age range where new evidence has come out recently – researchers have also been investigating what happens to older women.
In England, Wales and Northern Ireland, women continue to be invited for screening every five years between the ages of 50 and 64. And in Scotland women receive an invitation every three years up to the age of 60.
But a study a few months ago showed that being screened after their 60th birthday protected women from cervical cancer even into their eighties, though the level of protection dropped over time.
So what’s the take home message from this? It’s still important to take up screening when you’re in your sixties. But also, in future, as our life expectancy increases, we may need to start reconsidering the upper age limit for screening.
Improving the cervical screening programme
All this may sound as though we think the cervical screening programme is perfect just the way it is. It’s certainly very effective, saving around 5,000 lives a year in the UK, but there are also improvements that could make it even better.
One change that we’d like to see is HPV testing as the main type of cervical screening test, rather than the existing Liquid Based Cytology (LBC) test.
The former looks for DNA from the human papillomavirus (HPV) that causes cervical cancer, while the latter looks for signs of abnormal cells down a microscope.
HPV testing is used as a ‘secondary’ test and, since 2008, women with a borderline result or ‘mild abnormalities’ from LBC have their samples tested for the virus to see whether they need further follow up.
Research has shown that HPV testing is better at preventing cervical cancer than the current test, and could prevent an additional 600 cases of cervical cancer a year if the tests were swapped around.
As a result, the screening programme has begun rolling this out with a small proof-of-concept programme – women in certain areas will first have their sample tested for HPV and it will only be checked for abnormal cells if HPV is found in their sample.
This won’t change how screening works from a woman’s point of view – the way the sample is collected will stay the same. And because HPV testing works better than LBC, women who test negative for the virus can also safely wait longer before their next appointment – maybe up to five or six years instead of three.
This would reduce the number of tests they need and potentially save the NHS money as well as saving lives.
The pilots are happening in six areas of England. But there seems to be a lack of information about what happens next – we’d like to see plans in place now to extend and roll out HPV testing as the ’main’ test as soon as the pilots are over.
These sorts of changes can only be made by looking at the evidence from research. The evidence shows that attempts to improve the cervical screening programme by lowering the age range won’t help. But making the switch to HPV testing could.
By planning for this now, more lives will be saved, sooner.
The future of cervical screening?
Cervical screening is an effective, evidence-based way to prevent cervical cancer, but it isn’t the only option.
Infection with HPV is behind almost all cervical cancers, and a vaccine against the virus is now offered to young women, which is a very effective way of preventing infections.
So it’s likely that, in future, there will need to be more changes to how cervical screening works, to take account of the fact that more and more women of screening age will have been vaccinated.
They’ll still benefit from screening (as the vaccine doesn’t prevent 100 per cent of cases), but we need research to tell us how best to screen vaccinated women, and whether this will vary over a woman’s lifetime.
In the meantime, it’s important that vaccinated women still go for screening.
It’s critical that we and others continue to monitor and study existing screening programmes, to ensure they are working as they should be, now and into the future.
And so that they save as many lives as possible.
Jess Kirby is a senior health information manager at Cancer Research UK
Image of researchers and microscope from Wikimedia Commons